Imidazopyridyl compounds as aldosterone synthase inhibitors

Abstract

This invention relates to imidazopyridyl compounds of the structural formula: I or their pharmaceutically acceptable salts, wherein the variable are defined herein. The inventive compounds selectively inhibit aldosterone synthase. This invention also provides for pharmaceutical compositions comprising the compounds of formula I or their salts as well as potentially to methods for the treatment, amelioration or prevention of conditions that could be treated by inhibiting aldosterone synthase.

##STR00001##

Description

RELATED APPLICATION

This application claims benefit to provisional application U.S. Ser. No. 61/537,910, filed 22 Sep. 2012, herein incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to imidazopyridyl compounds, which selectively inhibit aldosterone synthase (CYP11B2) with diminished inhibition or affect on steroid-11-β-hydroxylase (CYP11B1) inhibitors. The inventive compounds potentially have utility in treating cardiovascular diseases such as hypertension or heart failure. The present invention also relates to pharmaceutical compositions comprising the inventive compounds as well as processes for their preparation.

BACKGROUND OF THE INVENTION

Aldosterone is a steroid hormone secreted in the adrenal cortex. In primary cells of the distal tubules and collecting ducts of the kidney, aldosterone binding to the mineralocorticoid receptor (MR) results in the retention of sodium and water and excretion of potassium, which in turn leads to increased blood pressure. Aldosterone also causes inflammation that leads to fibrosis and remodeling in the heart, vasculature and kidney. This inflammation may proceed by MR-dependent as well as MR-independent mechanisms (Gilbert, K. C. et al., Curr. Opin. Endocrinol. Diabetes Obes., vol. 17, 2010, pp. 199-204).

Mineralocorticoid receptor antagonists (MRAs), such as spironolactone and eplerenone, have been used previously to block the effects of aldosterone binding to MR. When given in addition to standard therapies such as angiotensin-converting enzyme (ACE) inhibitors and loop diuretics, the nonselective MRA spironolactone and the selective MRA eplerenone significantly reduced morbidity and mortality in patients with heart failure or myocardial infarction (Pitt, B. et al., New Engl. J. Med., vol. 341, 1999, pp. 709-717; Pitt, B. et al., New Engl. J. Med., vol. 348, 2003, pp. 1382-1390). However, the nonselective MRA spironolactone can also bind to and act at other steroid receptors, and as a consequence its use is associated with sexual side effects such as gynecomastia, dysmenorrhoea and impotence (Pitt, B. et al., New Engl. J. Med., vol. 341, 1999, pp. 709-717; MacFadyen, R. J. et al., Cardiovasc. Res., vol. 35, 1997, pp 30-34; Soberman, J. E. et al., Curr. Hypertens. Rep., vol. 2, 2000, pp 451-456). Additionally, both spironolactone and eplerenone are known to cause elevated plasma potassium levels (hyperkalemia) and elevated aldosterone levels.

An alternative method of blocking the effects of aldosterone is to inhibit its biosynthesis. CYP11B2 is a mitochondrial cytochrome P450 enzyme that catalyzes the final oxidative steps in the conversion of 11-deoxycorticosterone, a steroidal precursor, to aldosterone (Kawamoto, T. et al., Proc. Natl. Acad. Sci. USA, vol. 89, 1992, pp. 1458-1462). Compounds that inhibit CYP11B2 should thus inhibit the formation of aldosterone. Such compounds, particularly those of nonsteroidal structure, should provide the beneficial effects of MRAs, without the adverse effects derived from steroid receptor binding or MR-independent inflammatory pathways. The art has recognized that reducing aldosterone levels by inhibiting aldosterone synthase could represent a new pharmaceutical strategy that might be useful in treating a disorder or disease characterized by increased stress hormone levels and/or decreased androgen hormone levels in a patient (WO2011/088188 to Novartis). Compounds possessing this activity might have the potential to treat disease states such as heart failure, cachexia, acute coronary syndrome, Cushing's syndrome or metabolic syndrome.

CYP11B1 is a related enzyme that catalyzes the formation of glucocorticoids, such as cortisol, an important regulator of glucose metabolism. Because human CYP11B2 and CYP11B1 are greater than 93% homologous, it is possible for nonselective compounds to inhibit both enzymes (Kawamoto, T. et al., Proc. Natl. Acad. Sci. USA, vol. 89, 1992, pp 1458-1462; Taymans, S. E. et al., J. Clin. Endocrinol. Metab., vol. 83, 1998, pp 1033-1036). It would be preferable, however, for therapeutic agents to selectively inhibit CYP11B2 and the formation of aldosterone with diminished inhibition of, or affect on, CYP11B1 and the production of cortisol.

WO 2009/135651 to Elexopharm describes 6-pyridin-3yl-3,4,-dihydro-1H-quinolin-2-one derivatives as being CYP11B2 inhibitors. Two compounds described therein are lactam derivatives of the formula:

##STR00002##
Structurally similar lactam and thiolactam compounds are disclosed by Lucas et al., J. Med. Chem. 2008, 51, 8077-8087; those compounds are said to be potential inhibitors of CYP11B2. Lucas et al. in J. Med. Chem. 2011, 54, 2307-2309 describes certain pyridine substituted 3,4-dihydro-1H-quinolin-2-ones as being highly potent as selective inhibitors of CYP11B2. An abstract of a dissertation reports that a series of novel heterocyclic-substituted 4,5-dihydro-[1,2,4]triazolo[4,3a]quinolones was evaluated for its aldosterone synthase activity; one of the compounds is reported as exhibiting excellent selectivity of CYP11B2 over CYP11B1.

Benzimidazole derivatives are also known in the art to treat various disease states. For example, U.S. Pat. No. 6,897,208 to Aventis Pharmaceuticals describes compounds of the formula:

##STR00003##
wherein R¹ is an optionally substituted aryl or heteroaryl group and A₅ is H or alkyl. These compounds are said to be kinase inhibitors. Other benzimidazoles derivatives are known in the art. For example, WO2002/46168 A1 to AstraZeneca describes benzimidazoles derivatives that are useful in the treatment or prophylaxis of Alzheimer's disease, anxiety disorders, depressive disorders, osteoporosis, cardiovascular disease, rheumatoid arthritis or prostate cancer. US2007/0270420 A1 to Vertex Pharmaceuticals describes benzimidazole compounds that are useful of inhibitors of GSK-3 and Lck protein kineases. Other benzimidazole derivatives are described in US 2009/0018124 A1, WO2004/0862638, WO2008/073451 A1 and US 2005/0272756 A1.

Novartis in US 2010/0261698 A1 describes indole derivatives of the formula:

##STR00004##
Novatis indicates that these compounds inhibit aldosterone synthase and may be useful in the treatment of disease states such as heart failure and hypertension. In WO2010/130,796 A1 and WO2011/061168, Novartis discloses aryl-pyridine derivatives that are said to inhibit aldosterone synthase.

US 2009/0221591 A1 to Universitat des Saarlandes also discloses compounds that inhibit CYP11B1 and CYP11B2. WO 2009/135651 to Universitat des Saarlandes teaches that compounds of the formula:

##STR00005##
possess the ability to inhibit aldosterone synthase.

WO1999/400094 Bayer AG discloses oxazolidinones with azol-containing tricycles as having antibacterial activity.

U.S. Pat. No. 7,381,825 to Takeda describes histone deacetylase inhibitors of the formula
Z-Q-L-M
where Q is a substituted or unsubstituted aromatic ring, L is a substituent providing between 0-10 atoms separation between M and the remainder of the compound, M is a substituent capable of complexing with a deacetylase catalytic site and/or metal ion, and Z is list of bicyclic groups, including but not limited to

##STR00006##
where X is CR₁₂ or N. These compounds are said to be useful in treating cell-proliferative diseases such as, for example, leukemia, melanoma, bladder cancer, etc.

SUMMARY OF THE INVENTION

In its many embodiments, the present invention provides for novel imidazopyridyl compounds, which are inhibitors of CYP11B2, or metabolites, stereoisomers, salts, solvates or polymorphs thereof, processes of preparing such compounds, pharmaceutical compositions comprising one or more such compounds, processes of preparing pharmaceutical compositions comprising one or more such compounds and potentially methods of treatment, inhibition or amelioration of one or more disease states associated with inhibiting CYP11B2 by administering an effective amount at least one of the inventive imidazopyridyl compounds to a patient in need thereof.

In one aspect, the present application discloses a compound or a pharmaceutically acceptable salt, metabolite, solvate, prodrug or polymorph of said compound, said compound having the general structure shown in Formula I

##STR00007##

or a pharmaceutically acceptable salt thereof

wherein:

Ring A is attached to Ring B via positions D and E and is:

##STR00008##

D is C;

E is N;

R¹ is H or alkyl;

R² is halogen; —CN; —OR⁷; —N(R¹⁰)C(O)R⁷; —NR¹¹R¹²; —C(O)R⁷; —C(O)N(R¹¹)(R¹²); —C(O)OR⁷; —S(O)_m—R⁷; alkyl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, —OR⁷, NR⁸R⁹, CN, N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷, or —S(O)_m—R⁷; cycloalkyl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, —OR⁷, —NR⁸R⁹, —CN, —N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷ or —S(O)_m—R⁷; heterocycloalkyl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, —OR⁷, —CN, —NR⁸R⁹—N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷ or —S(O)_m—R⁷; aryl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, cycloalkyl, —OR⁷, —CN, —NR⁸R⁹—N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷, or —S(O)_m—R⁷; or heteroaryl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, cycloalkyl, —OR⁷, —CN, —NR⁸R⁹, N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷ or —S(O)_m—R⁷;

R³ is H; halogen; —CN; alkyl optionally substituted one or more times (e.g., 1 to 4 times) by halogen or cycloalkyl optionally substituted once or twice by alkyl or halogen; cycloalkyl optionally substituted once or twice by alkyl or halogen; or —C(O)OR⁷;

R⁴ is H; halogen; —CN; —OR⁷; —NR⁸R⁹; —N(R¹⁰)C(O)OR⁷; —C(O)OR⁷; —C(O)N(R⁸)(R⁹); —C(O)OR⁷; —N(R¹⁰)S(O)₂—OR⁷; or —S(O)_m—OR⁷; alkyl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, —OR⁷, —NR⁸R⁹, —CN, N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷, —N(R¹⁰)S(O)₂—R⁷ or —S(O)_nR⁷; cycloalkyl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, —OR⁷, —NR⁸R⁹, —CN, N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷ or —S(O)_m—R⁷; aryl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, cycloalkyl, —OR⁷, —CN, —NR⁸R⁹—N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷ or —S(O)_m—R⁷; heterocycloalkyl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, —OR⁷, —CN, —NR⁸R⁹, —N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷ or —S(O)_m—R⁷; or heteroaryl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, cycloalkyl, —OR⁷, —CN, —NR⁸R⁹, —N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷ or —S(O)_m—R⁷;

R⁵ is H; halogen; —CN; —OR⁷; —NR⁸R⁹; —N(R¹⁰)C(O)OR⁷; —C(O)N(R⁸)(R⁹); —C(O)R⁷; —C(O)OR⁷; —N(R¹⁰)S(O)₂—OR⁷; —S(O)_n—R⁷; alkyl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, —OR⁷, —NR⁸R⁹, —CN, —N(R¹¹)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷, —N(R¹⁰)S(O)₂—R⁷, or —S(O)—R⁷; cycloalkyl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, —OR⁷, —NR⁸R⁹, —CN, —N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷ or —S(O)_m—R⁷; aryl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, cycloalkyl, —CN, —NR⁸R⁹—N(R¹⁰)C(O)(R⁷), —C(O)N(R⁸)(R⁹), —C(O)OR⁷ or —S(O)_m—R⁷; heterocycloalkyl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, cycloalkyl, —CN, —NR⁸R⁹—N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷ or —S(O)_m—R⁷; or heteroaryl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, cycloalkyl, —OR⁷, —CN, —NR⁸R⁹, —N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷ or —S(O)_m—R⁷;

• • or R⁴ and R⁵ are joined together to form a 5- to 7-membered carbocyclic or heterocyclic ring that is fused to the pyridyl ring to which R⁴ and R⁵ are attached, wherein the ring formed by R⁴ and R⁵ is optionally substituted by 1 to 3 R⁶;

R⁶ is independently H; halogen; —CN; —OR⁷; —NR⁸R⁹; —N(R¹⁰)C(O)OR⁷; —C(O)N(R⁷)(R⁸); —C(O)N(R⁸)(R⁹); —C(O)OR⁷; —S(O)_m—R⁷; alkyl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, —OR⁷, —NR⁸R⁹, —CN, —N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷ or —S(O)_m—R⁷; cycloalkyl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, —NR⁸R⁹, —CN, —N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷ or —S(O)_m—R⁷; aryl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, cycloalkyl, —CN, —NR⁸R⁹—N(R¹⁰)C(O)(R⁷), —C(O)N(R⁷)(R⁸), —C(O)OR⁷ or —S(O)_m—R⁷; heterocycloalkyl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, —OR⁷, —CN, —NR⁸R⁹—N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷ or —S(O)_m—R⁷; or heteroaryl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, cycloalkyl, —OR⁷, —CN, —NR⁸R⁹, —N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷ or —S(O)_m—R⁷;

R⁷ is independently H; alkyl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, —OR¹⁰, —NR⁸R⁹, —CN, —N(R¹⁰)C(O)R¹⁰, —C(O)N(R⁸)(R⁹), C(O)OR¹⁰ or —S(O)_m—R¹⁰; cycloalkyl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, —OR¹⁰, —NR⁸R⁹, —CN, —N(R¹⁰)C(O)R¹⁰, —C(O)N(R⁸)(R⁹), —C(O)OR¹⁰ or —S(O)_m—R¹⁰; aryl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, cycloalkyl, —OH, —OR¹⁰, —NR⁸R⁹, —CN, —N(R¹⁰)C(O)R¹⁰, —C(O)N(R⁸)(R⁹), —C(O)OR¹⁰ or —S(O)_m—R¹⁰; or heteroaryl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, cycloalkyl, —OR¹⁰, —NR⁸R⁹, —CN, —N(R⁹)C(O)R¹⁰, —C(O)N(R⁸)(R⁹), —C(O)OR¹⁰ or —S(O)_m—R¹⁰;

R⁸ is independently H or alkyl;

R⁹ is independently H or alkyl;

• • or R⁸ and R⁹ are joined together with the nitrogen to which they are attached form a saturated 5- to 7-membered heterocyclic ring;

R¹⁰ is independently H or alkyl;

R¹¹ is independently H; alkyl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, —OR⁷, —NR⁸R⁹, —CN, —N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷ or —S(O)_m—R⁷; cycloalkyl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, —OR⁷, —NR⁸R⁹, —CN, —N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁸ or —S(O)_m—R⁸; aryl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, cycloalkyl, —OR⁷, —CN, —NR⁸R⁹—N(R¹⁰)C(O)(R⁷), —C(O)N(R⁷)(R⁸), —C(O)OR⁷ or —S(O)_m—R⁷; heterocycloalkyl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, —OR⁷, —CN, —NR⁸R⁹—N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷ or —S(O)_m—R⁷; or heteroaryl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, cycloalkyl, —OR⁷, —CN, —NR⁸R⁹, —N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷ or —S(O)_m—R⁷;

R¹² is independently H; alkyl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, —OR⁷, —NR⁸R⁹, —CN, —N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷ or —S(O)_m—R⁷; cycloalkyl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, —NR⁸R⁹, —CN, N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁸ or —S(O)_m—R⁸; aryl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, cycloalkyl, —CN, —NR⁸R⁹—N(R¹⁰)C(O)(R⁷), —C(O)N(R⁷)(R⁸), —C(O)OR⁷ or —S(O)_m—R⁷; heterocycloalkyl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, —OR⁷, —CN, —NR⁸R⁹—N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷ or —S(O)_m—R⁷; or heteroaryl optionally substituted one or more times (e.g., 1 to 4 times) by halogen, alkyl, haloalkyl, cycloalkyl, —OR⁷, —CN, —NR⁸R⁹, N(R¹⁰)C(O)R⁷, —C(O)N(R⁸)(R⁹), —C(O)OR⁷ or —S(O)_m—R⁷;

a is 0, 1, 2, 3, or 4 (e.g., 0, 1 or 2);

n is 1 or 2; and

m is 0, 1 or 2.

Another aspect of the present invention is pharmaceutical compositions comprising a therapeutically effective amount of at least one compound of Formula I or a pharmaceutically acceptable salt thereof and a pharmaceutically acceptable carrier.

Another aspect of the present invention is pharmaceutical compositions comprising a therapeutically effective amount of at least one compound of Formula I or a pharmaceutically acceptable salt thereof, a therapeutically effective amount of at least one additional therapeutic agent and a pharmaceutically acceptable carrier.

Another aspect of the present invention potentially is the prevention of one or more disease states associated with inhibiting CYP11B2 by administering an effective amount at least one of the inventive imidazopyridyl compounds to a patient in need thereof.

It is further contemplated that the combination of the invention could be provided as a kit comprising in a single package at least one compound of Formula I or a pharmaceutically acceptable salt thereof in a pharmaceutical composition, and at least one separate pharmaceutical composition, such as, for example a separate pharmaceutical composition comprising a therapeutic agent.

The compounds of the present invention could be useful in the treatment, amelioration or prevention of one or more conditions associated with inhibiting CYP11B2 by administering a therapeutically effective amount of at least one compound of Formula I or a pharmaceutically acceptable salt thereof to a mammal in need of such treatment. Conditions that could be treated or prevented by inhibiting CYP11B2 include hypertension, heart failure such as congestive heart failure, diastolic dysfunction, left ventricular diastolic dysfunction, heart failure (including congestive heart failure), diastolic dysfunction, left ventricular diastolic dysfunction, diastolic heart failure, systolic dysfunction, hypokalemia, renal failure (including chronic renal failure), restenosis, syndrome X, nephropathy, post-myocardial infarction, coronary heart diseases, increased formation of collagen, fibrosis and remodeling following hypertension and endothelial dysfunction, cardiovascular diseases, renal dysfunction, liver diseases, vascular diseases, cerebrovascular diseases, retinopathy, neuropathy, insulinopathy, endothelial dysfunction, ischemia, myocardial and vascular fibrosis, myocardial necrotic lesions, vascular damage, myocardial necrotic lesions, myocardial infarction, left ventricular hypertrophy, cardiac lesions, vascular wall hypertrophy, endothelial thickening or fibrinoid necrosis of coronary arteries.

The compounds of the present invention also might be useful in treating one or more conditions characterized by increased stress hormone levels and/or decreased androgen hormone levels in a mammal by administering a therapeutically effective amount of at least one compound of Formula I or a pharmaceutically acceptable salt thereof to a mammal in need of such treatment. Conditions characterized by increased stress hormone levels and/or decreased androgen hormone levels in a mammal include, for example, heart failure (e.g., acute heart failure, acute decompensated heart failure, chronic heart failure, chronic heart failure with impaired exercise tolerance or chromic heart failure with muscle weakness), cachexia (e.g., cardiac cachexia, COPD-induced cachexia, cirrhosis-induced cachexia, tumor-induced cachexia or viral (HIV)-induced cachexia), acute coronary syndrome, Cushing's syndrome or metabolic syndrome.

Another aspect of the present invention is the use of a compound of Formula I or a pharmaceutically acceptable salt thereof for the manufacture of a medicament for the treatment, amelioration or prevention of one or more conditions associated with inhibiting CYP11B2 in a patient.

This invention further relates to process for the preparation of the compounds of Formula I or their pharmaceutically acceptable salts. Moreover, this invention also relates to the use of the compounds of Formula I or their pharmaceutically acceptable salts to validate in vitro assays, such as, for example the V79-Human-CYP11B2 and V79-Human-CYP11B1 discussed later in the application.

These and other objectives will be evident from the description of the invention contained herein.

DETAILED DESCRIPTION

In an embodiment, the present invention provides compounds represented by structural Formula I or pharmaceutically acceptable salt thereof, wherein the various moieties are as described as above.

Another embodiment of the present invention is compounds or their pharmaceutically acceptable salts of Formula I represented by structural Formula II

##STR00009##

wherein R², R³, R⁴, R⁵ and a are as defined in Formula I.

Another embodiment of the present invention is compounds or their pharmaceutically acceptable salts of Formula I represented by structural Formula III

##STR00010##

wherein R¹, R³, R⁴, R⁵ and a are as defined in Formula I.

Another embodiment of the present invention is compounds or their pharmaceutically acceptable salts of Formula I represented by structural Formula IV

##STR00011##

wherein R², R³ and a are as defined in Formula I and b is 0, 1 or 2 (e.g, where b is 0, or where b is 1 or 2 and R⁶ is alkyl or halo).

Another embodiment of the present invention is compounds or their pharmaceutically acceptable salts of Formula I represented by structural Formula V

##STR00012##

wherein R¹, R² and a are as defined in Formula I and b is 0, 1 or 2 (e.g, where b is 0, or where b is 1 or 2 and R⁶ is alkyl or halo).

Another embodiment of the present invention is compounds or their pharmaceutically acceptable salts of any of the embodiments of Formulae I through V, a is 0 or a is 1 or 2 and R² is independently halogen (e.g., F or Cl), —CN, alkyl (e.g., methyl, ethyl, n-propyl, i-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl), —OR⁷ (where R⁷ is H, alkyl (e.g., methyl, ethyl, n-propyl, i-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl), or haloalkyl (e.g., —CF₃)), haloalkyl (e.g., —CF₃), cycloalkyl (e.g., cyclopropyl or cyclohexyl) or phenyl optionally substituted by halogen.

Another embodiment of the present invention is compounds or their pharmaceutically acceptable salts of any the embodiments of Formulae I through V described above where R³ is H, halogen, —CN, alkyl (e.g., methyl, ethyl, n-propyl, propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl), or cycloalkyl (e.g., cyclopropyl or cyclohexyl).

Another embodiment of the present invention is compounds or their pharmaceutically acceptable salts of any of the embodiments of Formulae I through III above where R⁴ is H, halogen (e.g., —F or Cl), —CN, alkyl (e.g., methyl or ethyl) or cycloalkyl (e.g., cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl).

Another embodiment of the present invention is compounds or their pharmaceutically acceptable salts of any of the embodiments of Formulae I through III above where R⁴ is H or alkyl (e.g., methyl or ethyl).

Another embodiment of the present invention is compounds or their pharmaceutically acceptable salts of any of the embodiments of Formulae I through III above where R⁵ is H, halogen (e.g., —F or Cl), —CN, alkyl (e.g., methyl, ethyl, n-propyl, propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl), —OR⁷ (where R⁷ is H, alkyl (e.g., methyl, ethyl, n-propyl, i-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl) or haloalkyl (e.g., —CF₃)), haloalkyl (e.g., —CF₃) or phenyl optionally substituted by halogen, —OR⁷ (where R⁷ is H, alkyl (e.g., methyl, ethyl, n-propyl, i-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl)) or haloalkyl (e.g., —CF₃).

Another embodiment of the present invention is compounds or their pharmaceutically acceptable salts thereof of any of the embodiments of Formula I through III described above where R⁴ is H and R⁵ is H, halogen (e.g., —F or —Cl), —CN, alkyl (e.g., methyl, ethyl, n-propyl, i-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl), —OR⁷ (where R⁷ is H, alkyl (e.g., methyl, ethyl, n-propyl, i-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl) or haloalkyl (e.g., —CF₃)), haloalkyl (e.g., —CF₃) or phenyl optionally substituted by halogen, —OR⁷ (where R⁷ is H, alkyl (e.g., methyl, ethyl, n-propyl, i-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl) or haloalkyl (e.g., —CF₃)).

Another embodiment of the present invention is compounds or their pharmaceutically acceptable salts thereof of any of the embodiments of Formulae I through III described above where R⁵ is C(O)OR⁷ (e.g., R⁷ is C₁-C₄-alkyl or phenyl, optionally substituted by halogen or haloalkyl).

Another embodiment of the present inventions is compounds or their pharmaceutically acceptable salts thereof of any of the embodiments of Formula I through III described above or their pharmaceutically acceptable salts thereof where R⁴ is H and R⁵ is a group of the formula:

##STR00013##

where:

• • R^a is H, OH, or —C₁-C₃-alkyl optionally substituted with 1 to 3 —F (e.g. CF₃);
  • R^b is H, —OH, or —C₁-C₃-alkyl optionally substituted with 1 to 3 —F (e.g. CF₃);
  • R^c is —C₁-C₃-alkyl optionally substituted with 1 to 3 —F (e.g. —CF₃), is —OC₁-C₃-alkyl, —N(H)S(O)₂—C₁-C₃-alkyl, optionally substituted with 1 to 3 —F (e.g. —CF₃), —N(H)C(O)C₁-C₃-alkyl, optionally substituted with 1 to 3 —F (e.g. —CF₃).

As used above, and throughout this disclosure, the following terms, unless otherwise indicated, shall be understood to have the following meanings:

“Mammal” means humans and other mammalian animals.

The following definitions apply regardless of whether a term is used by itself or in combination with other terms, unless otherwise indicated. Therefore, the definition of “alkyl” applies to “alkyl” as well as the “alkyl” portions of “hydroxyalkyl”, “haloalkyl”, “alkoxy”, etc.

“Alkyl” means an aliphatic hydrocarbon group which may be straight or branched and comprising about 1 to about 20 carbon atoms in the chain. Preferred alkyl groups contain about 1 to about 12 carbon atoms in the chain. More preferred alkyl groups contain about 1 to about 6 carbon atoms in the chain. Branched means that one or more lower alkyl groups such as methyl, ethyl or propyl, are attached to a linear alkyl chain. “Lower alkyl” means a group having about 1 to about 6 carbon atoms in the chain which may be straight or branched.

“Halo” refers to fluorine, chlorine, bromine or iodine radicals. Examples are fluoro, chloro or bromo.

“Halogen” means fluorine, chlorine, bromine, or iodine.

“Haloalkyl” means a halo-alkyl-group in which the alkyl group is as previously described. The bond to the parent moiety is through the alkyl. Non-limiting examples of suitable haloalkyl groups include fluoromethyl, difluoromethyl, —CH₂CF₃, —CH₂CHF₂—CH₂CH₂F, or an alkyl group with one or more terminal carbons tri-substituted with a halogen (e.g., —F) such as, for example —C₁-C₃alkyl-CF₃, —CH(CH₃)(CF₃), —CH(CF₃)₂ and the like.

“Cycloalkyl” means a non-aromatic mono- or multicyclic ring system comprising about 3 to about 10 carbon atoms, preferably about 5 to about 10 carbon atoms. Preferred cycloalkyl rings contain about 5 to about 7 ring atoms. The cycloalkyl can be optionally substituted with one or more “ring system substituents” which may be the same or different, and are as defined above. Non-limiting examples of suitable monocyclic cycloalkyls include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and the like. Non-limiting examples of suitable multicyclic cycloalkyls include 1-decalinyl, norbornyl, adamantyl and the like, as well as partially saturated species such as, for example, indanyl, tetrahydronaphthyl and the like.

“Aryl” means an aromatic monocyclic or multicyclic ring system comprising about 6 to about 14 carbon atoms, preferably about 6 to about 10 carbon atoms. Non-limiting examples of suitable aryl groups include phenyl, naphthyl, indenyl, tetrahydronaphthyl and indanyl.

“Heterocycloalkyl” means a non-aromatic saturated monocyclic or multicyclic ring system comprising about 3 to about 10 ring atoms, preferably about 5 to about 10 ring atoms, in which one or more of the atoms in the ring system is an element other than carbon, for example nitrogen, oxygen or sulfur, alone or in combination. There are no adjacent oxygen and/or sulfur atoms present in the ring system. Preferred heterocyclyls contain about 5 to about 6 ring atoms. The prefix aza, oxa or thia before the heterocycloalkyl root name means that at least a nitrogen, oxygen or sulfur atom respectively is present as a ring atom. Any —NH in a heterocycloalkyl ring may exist protected such as, for example, as an —N(Boc), —N(CBz), —N(Tos) group and the like; such protections are also considered part of this invention. The nitrogen or sulfur atom of the heterocycloalkyl ring can be optionally oxidized to the corresponding N-oxide, S-oxide or S,S-dioxide. Non-limiting examples of suitable monocyclic heterocycloalkyl rings include piperidyl, pyrrolidinyl, piperazinyl, morpholinyl, thiomorpholinyl, thiazolidinyl, 1,3-dioxanyl, 1,4-dioxanyl, tetrahydrofuranyl, tetrahydrothiopyranyl, oxetanyl, tetrahydrothiophenyl, lactam, lactone, and the like.

“Heteroaryl” means an aromatic monocyclic or multicyclic ring system comprising about 5 to about 14 ring atoms, preferably about 5 to about 10 ring atoms, in which one or more of the ring atoms is an element other than carbon, for example nitrogen, oxygen or sulfur, alone or in combination, provided that the rings do not include adjacent oxygen and/or sulfur atoms. N-oxides of the ring nitrogens are also included, as well as compounds wherein a ring nitrogen is substituted by an alkyl group to form a quaternary amine. Preferred heteroaryls contain about 5 to about 6 ring atoms. The prefix aza, oxa or thia before the heteroaryl root name means that at least a nitrogen, oxygen or sulfur atom respectively, is present as a ring atom. A nitrogen atom of a heteroaryl can be optionally oxidized to the corresponding N-oxide. Non-limiting examples of suitable heteroaryls include pyridyl, pyrazinyl, furanyl, thienyl, pyrimidinyl, pyridone (including N-substituted pyridones), isoxazolyl, isothiazolyl, oxazolyl, thiazolyl, pyrazolyl, oxadiazolyl, tetrazolyl, pyrimidyl, furazanyl, pyrrolyl, pyrazolyl, triazolyl, 1,2,4-thiadiazolyl, pyrazinyl, pyridazinyl, quinoxalinyl, phthalazinyl, oxindolyl, naphthyridyl (e.g., 1,5 or 1,7), pyrido[2,3]imidazolyl, imidazo[1,2-a]pyridinyl, imidazo[2,1-b]thiazolyl, benzofuranyl, benzofurazanyl, indolyl, azaindolyl, benzimidazolyl, benzothienyl, quinolinyl, imidazolyl, thienopyridyl, quinazolinyl, thienopyrimidyl, pyrrolopyridyl, imidazopyridyl, isoquinolinyl, benzoazaindolyl, 1,2,4-triazinyl, benzoxazolyl, benzothiazolyl, pyridopyrimidinyl, 7-azaindolyl and the like. The term “heteroaryl” also refers to partially saturated heteroaryl moieties such as, for example, tetrahydroisoquinolyl, tetrahydroquinolyl and the like. All positional isomers are contemplated, e.g., 2-pyridyl, 3-pyridyl and 4-pyridyl.

It should be noted that in heterocycloalkyl ring systems of this invention, there are no hydroxyl groups on carbon atoms adjacent to a N, O or S, as well as there are no N or S groups on carbon adjacent to another heteroatom. Thus, for example, in the ring:

##STR00014##
there is no —OH attached directly to carbons marked 2 and 5.

It should also be noted that tautomeric forms such as, for example, the moieties:

##STR00015##
are considered equivalent in certain embodiments of this invention.

When R⁴ and R⁵ are joined together to form a 5-7 membered carbocyclic ring that is fused to the pyridyl ring to which R⁴ and R⁵ are attached, “carbocyclic” means a cycloalkyl, aryl or partially unsaturated ring composed of 5-7 carbon atoms wherein two of the carbons are shared between the fused rings. When R⁴ and R⁵ are joined together to form a 5-7 membered heterocyclic ring that is fused to the pyridyl ring to which R⁴ and R⁵ are attached, “heterocyclic” means a fully saturated, partially saturated or aromatic ring composed of carbon atoms and one, two or three heteroatoms selected from N, S, or O, wherein two of the carbons are shared between the fused rings. Representative ring include:

##STR00016##

When a moiety can be optionally substituted, it means that each carbon and heteroatom (when present) available for substitution in the given moiety may be independently unsubstituted or substituted with specified number of substituents that are the same or different at each occurrence and which result in the creation of a stable structure as is understood to be reasonable by one skilled in the art.

Unless expressly depicted or described otherwise, variables depicted in a structural formula with a “floating” bond, such as R² in structural Formula III are permitted on any available carbon atom in the ring to which each is attached.

When R⁸ and R⁹ together with the nitrogen to which they are attached form a saturated 5- to 7-membered heterocyclic ring, this means a saturated heterocyclic ring composed of, in addition to the one nitrogen atom, carbon atoms and optionally one additional heteroatom selected from N, S or O. Representative examples include:

##STR00017##

The present invention encompasses all stereoisomeric forms of the compounds of Formula I. Centers of asymmetry that are present in the compounds of Formula I can all independently of one another have (R) configuration or (S) configuration. When bonds to the chiral carbon are depicted as straight lines in the structural Formulas of the invention, it is understood that both the (R) and (S) configurations of the chiral carbon, and hence both enantiomers and mixtures thereof, are embraced within the Formula. Similarly, when a compound name is recited without a chiral designation for a chiral carbon, it is understood that both the (R) and (S) configurations of the chiral carbon, and hence individual enantiomers and mixtures thereof, are embraced by the name. The production of specific stereoisomers or mixtures thereof may be identified in the Examples where such stereoisomers or mixtures were obtained, but this in no way limits the inclusion of all stereoisomers and mixtures thereof from being within the scope of this invention.

The invention includes all possible enantiomers and diastereomers and mixtures of two or more stereoisomers, for example mixtures of enantiomers and/or diastereomers, in all ratios. Thus, enantiomers are a subject of the invention in enantiomerically pure form, both as levorotatory and as dextrorotatory antipodes, in the form of racemates and in the form of mixtures of the two enantiomers in all ratios. In the case of a cis/trans isomerism the invention includes both the cis form and the trans form as well as mixtures of these forms in all ratios. The preparation of individual stereoisomers can be carried out, if desired, by separation of a mixture by customary methods, for example by chromatography or crystallization, by the use of stereochemically uniform starting materials for the synthesis or by stereoselective synthesis. Optionally a derivatization can be carried out before a separation of stereoisomers. The separation of a mixture of stereoisomers can be carried out at an intermediate step during the synthesis of a compound of Formula I or it can be done on a final racemic product. Absolute stereochemistry may be determined by X-ray crystallography of crystalline products or crystalline intermediates which are derivatized, if necessary, with a reagent containing a stereogenic center of known configuration. Where compounds of this invention are capable of tautomerization, all individual tautomers as well as mixtures thereof are included in the scope of this invention. The present invention includes all such isomers, as well as salts, solvates (including hydrates) and solvated salts of such racemates, enantiomers, diastereomers and tautomers and mixtures thereof.

Reference to the compounds of this invention as those of a specific formula or embodiment, e.g., Formula I (which includes the compounds of Formulae II-V all embodiments herein) or any other generic structural formula or specific compound described or claimed herein, is intended to encompass the specific compound or compounds falling within the scope of the formula or embodiment, including salts thereof, particularly pharmaceutically acceptable salts, solvates of such compounds and solvated salt forms thereof, where such forms are possible unless specified otherwise.

In the compounds of Formula I, the atoms may exhibit their natural isotopic abundances, or one or more of the atoms may be artificially enriched in a particular isotope having the same atomic number, but an atomic mass or mass number different from the atomic mass or mass number predominantly found in nature. The present invention is meant to include all suitable isotopic variations of the compounds of Formula I. For example, different isotopic forms of hydrogen (H) include protium (¹H) and deuterium (²H). Protium is the predominant hydrogen isotope found in nature. Enriching for deuterium may afford certain therapeutic advantages, such as increasing in vivo half-life or reducing dosage requirements, or may provide a compound useful as a standard for characterization of biological samples. Isotopically-enriched compounds within Formula Ia can be prepared without undue experimentation by conventional techniques well known to those skilled in the art or by processes analogous to those described in the Schemes and Examples herein using appropriate isotopically-enriched reagents and/or intermediates.

When the compounds of Formula I contain one or more acidic or basic groups the invention also includes the corresponding physiologically or toxicologically acceptable salts, in particular the pharmaceutically utilizable salts. Thus, the compounds of Formula I which contain acidic groups can be used according to the invention, for example, as alkali metal salts, alkaline earth metal salts or as ammonium salts. Examples of such salts include but are not limited to sodium salts, potassium salts, calcium salts, magnesium salts or salts with ammonia or organic amines such as, for example, ethylamine, ethanolamine, triethanolamine or amino acids. Compounds of Formula I which contain one or more basic groups, i.e. groups which can be protonated, can be used according to the invention in the form of their acid addition salts with inorganic or organic acids as, for example but not limited to, salts with hydrogen chloride, hydrogen bromide, phosphoric acid, sulfuric acid, nitric acid, benzenesulfonic acid, methanesulfonic acid, p-toluenesulfonic acid, naphthalenedisulfonic acids, oxalic acid, acetic acid, trifluoroacetic acid, tartaric acid, lactic acid, salicylic acid, benzoic acid, formic acid, propionic acid, pivalic acid, diethylacetic acid, malonic acid, succinic acid, pimelic acid, fumaric acid, maleic acid, malic acid, sulfaminic acid, phenylpropionic acid, gluconic acid, ascorbic acid, isonicotinic acid, citric acid, adipic acid, etc. If the compounds of Formula I simultaneously contain acidic and basic groups in the molecule the invention also includes, in addition to the salt forms mentioned, inner salts or betaines (zwitterions). Salts can be obtained from the compounds of Formula I by customary methods which are known to the person skilled in the art, for example by combination with an organic or inorganic acid or base in a solvent or dispersant, or by anion exchange or cation exchange from other salts. The present invention also includes all salts of the compounds of Formula I which, owing to low physiological compatibility, are not directly suitable for use in pharmaceuticals but which can be used, for example, as intermediates for chemical reactions or for the preparation of physiologically (i.e., pharmaceutically) acceptable salts.

Furthermore, compounds of the present invention may exist in amorphous form and/or one or more crystalline forms, and as such all amorphous and crystalline forms and mixtures thereof of the compounds of Formula I are intended to be included within the scope of the present invention. In addition, some of the compounds of the instant invention may form solvates with water (i.e., a hydrate) or common organic solvents. Such solvates and hydrates, particularly the pharmaceutically acceptable solvates and hydrates, of the instant compounds are likewise encompassed within the scope of this invention, along with un-solvated and anhydrous forms.

Any pharmaceutically acceptable pro-drug modification of a compound of this invention which results in conversion in vivo to a compound within the scope of this invention is also within the scope of this invention. For example, esters can optionally be made by esterification of an available carboxylic acid group or by formation of an ester on an available hydroxy group in a compound. Similarly, labile amides can be made. Pharmaceutically acceptable esters or amides of the compounds of this invention may be prepared to act as pro-drugs which can be hydrolyzed back to an acid (or —COO⁻ depending on the pH of the fluid or tissue where conversion takes place) or hydroxy form particularly in vivo and as such are encompassed within the scope of this invention. Examples of pharmaceutically acceptable pro-drug modifications include, but are not limited to, —C_1-6alkyl esters and —C_1-6alkyl substituted with phenyl esters.

Accordingly, the compounds within the generic structural formulas, embodiments and specific compounds described and claimed herein encompass salts, all possible stereoisomers and tautomers, physical forms (e.g., amorphous and crystalline forms), solvate and hydrate forms thereof and any combination of these forms, as well as the salts thereof, pro-drug forms thereof, and salts of pro-drug forms thereof, where such forms are possible unless specified otherwise.

Compounds of the present invention are effective at inhibiting the synthesis of aldosterone by inhibiting CYP11B2 (aldosterone synthase) and therefore might be useful agents for the therapy and prophylaxis of disorders that are associated with elevated aldosterone levels. Accordingly, an object of the instant invention is to provide a method for inhibiting aldosterone synthase, and more particularly selectively inhibiting CYP11B2, in a patient in need thereof, comprising administering a compound of Formula I to the patient in an amount effective to inhibit aldosterone synthesis, or more particularly to selectively inhibit CYP11B2, in the patient. A selective inhibitor of CYP11B2 is intended to mean a compound that preferentially inhibits CYP11B2 as compared to CYP11B1. The inhibition of CYP11B2, as well inhibition of CYP11B1, by the compounds of Formula I can be examined, for example, in the inhibition assays described below.

In general, compounds that have activity as aldosterone synthase inhibitors can be identified as those compounds which have an IC₅₀ of less than or equal to about 10 μM; preferably less than or equal to about 250 nM; and most preferably less than or equal to about 100 nM, in the V79-Human-CYP11B2 Assay described below. In general, aldosterone synthase inhibitors that are selective for inhibition of CYP11B2 as compared to CYP11B1 are those that show at least 3-fold greater inhibition for CYP11B2 compared to CYP11B1; preferably at least 20-fold inhibition for CYP11B2 compared to CYP11B1; and more preferably at least 100-fold greater inhibition for CYP11B2 compared to CYP11B1, in the V79-Human-CYP11B2 Assay as compared to the V79-Human-CYP11B1 Assay.

Due to their ability to inhibit CYP11B2, the compounds of the present invention might be useful to treat and/or ameliorate the risk for hypertension, hypokalemia, renal failure (e.g., chromic renal failure), restenosis, Syndrome X, nephropathy, post-myocardial infarction, coronary heart diseases, increased formation of collagen, fibrosis and remodeling following hypertension and endothelial dysfunction, cardiovascular diseases, renal dysfunction, liver diseases, vascular diseases, cerebrovascular diseases, retinopathy, neuropathy, insulinopathy, endothelial dysfunction, heart failure (e.g., congestive heart failure), diastolic heart failure, left ventricle diastolic dysfunction, diastolic heart failure, systolic dysfunction, ischemia, myocardial and vascular fibrosis, myocardial necrotic lesions, vascular damage, myocardial infarction, left ventricular hypertrophy, cardiac lesions, vascular wall hypertrophy, endothelial thickening or necrosis of coronary arteries.

The dosage amount of the compound to be administered depends on the individual case and is, as is customary, to be adapted to the individual circumstances to achieve an optimum effect. Thus, it depends on the nature and the severity of the disorder to be treated, and also on the sex, age, weight and individual responsiveness of the human or animal to be treated, on the efficacy and duration of action of the compounds used, on whether the therapy is acute or chronic or prophylactic, or on whether other active compounds are administered in addition to compounds of Formula I. A consideration of these factors is well within the purview of the ordinarily skilled clinician for the purpose of determining the therapeutically effective or prophylactically effective dosage amount needed to prevent, counter, or arrest the progress of the condition. It is expected that the compound will be administered chronically on a daily basis for a length of time appropriate to treat or prevent the medical condition relevant to the patient, including a course of therapy lasting days, months, years or the life of the patient.

In general, a daily dose of approximately 0.001 to 30 mg/kg, preferably 0.001 to 20 mg/kg, in particular 0.01 to 10 mg/kg (in each case mg per kg of bodyweight) is appropriate for administration to an adult weighing approximately 75 kg in order to obtain the desired results. The daily dose is preferably administered in a single dose or, in particular when larger amounts are administered, can be divided into several, for example two, three or four individual doses, and may be, for example, but not limited to, 0.1 mg, 0.25 mg, 0.5 mg, 0.75 mg, 1 mg, 1.25 mg, 1.5 mg, 2 mg, 2.5 mg, 5 mg, 10 mg, 20 mg, 40 mg, 50 mg, 75 mg, 100 mg, etc., on a daily basis. In some cases, depending on the individual response, it may be necessary to deviate upwards or downwards from the given daily dose.

The term “patient” includes animals, preferably mammals and especially humans, who use the instant active agents for the prevention or treatment of a medical condition. Administering of the drug to the patient includes both self-administration and administration to the patient by another person. The patient may be in need of treatment for an existing disease or medical condition, or may desire prophylactic treatment to prevent or reduce the risk of said disease or medical condition.

The term therapeutically effective amount is intended to mean that amount of a drug or pharmaceutical agent that will elicit the biological or medical response of a tissue, a system, animal or human that is being sought by a researcher, veterinarian, medical doctor or other clinician. A prophylactically effective amount is intended to mean that amount of a pharmaceutical drug that will prevent or reduce the risk of occurrence of the biological or medical event that is sought to be prevented in a tissue, a system, animal or human by a researcher, veterinarian, medical doctor or other clinician. The terms “preventing” or “prevention” as used herein refers to administering a compound before the onset of clinical symptoms.

It is understood that a specific daily dosage amount can simultaneously be both a therapeutically effective amount, e.g., for treatment of hypertension, and a prophylactically effective amount, e.g., for prevention of myocardial infarction.

In the methods of treatment of this invention, the compound may be administered via any suitable route of administration such as, for example, orally, parenterally, or rectally in dosage unit formulations containing conventional non-toxic pharmaceutically acceptable carriers, adjuvants and vehicles. The term parenteral as used herein includes subcutaneous injections, intravenous, intramuscular, intrasternal injection or infusion techniques. Oral formulations are preferred, particularly solid oral dosage units such as pills, tablets or capsules.

Accordingly, this invention also provides pharmaceutical compositions comprised of a compound of Formula I and a pharmaceutically acceptable carrier. For oral use, the pharmaceutical compositions of this invention containing the active ingredient may be in forms such as pills, tablets, troches, lozenges, aqueous or oily suspensions, dispersible powders or granules, emulsions, hard or soft capsules, or syrups or elixirs. Compositions intended for oral use may be prepared according to any method known to the art for the manufacture of pharmaceutical compositions and such compositions may contain one or more agents selected from the group consisting of sweetening agents, flavoring agents, coloring agents and preserving agents in order to provide pharmaceutically elegant and palatable preparations. Tablets contain the active ingredient in admixture with non-toxic pharmaceutically acceptable excipients, which are suitable for the manufacture of tablets. These excipients may be for example, inert diluents, such as calcium carbonate, sodium carbonate, lactose, mannitol, calcium phosphate or sodium phosphate; granulating and disintegrating agents, for example, corn starch, or alginic acid; binding agents, for example starch, gelatin or acacia, and lubricating agents, for example, magnesium stearate, stearic acid or talc. Pharmaceutical compositions may also contain other customary additives, for example, wetting agents, stabilizers, emulsifiers, dispersants, preservatives, sweeteners, colorants, flavorings, aromatizers, thickeners, diluents, buffer substances, solvents, solubilizers, agents for achieving a depot effect, salts for altering the osmotic pressure, coating agents or antioxidants.

Oral immediate-release and time-controlled release dosage forms may be employed, as well as enterically coated oral dosage forms. Tablets may be uncoated or they may be coated by known techniques for aesthetic purposes, to mask taste or for other reasons. Coatings can also be used to delay disintegration and absorption in the gastrointestinal tract and thereby provide a sustained action over a longer period. For example, a time delay material such as glyceryl monostearate or glyceryl distearate may be employed.

Formulations for oral use may also be presented as hard gelatin capsules wherein the active ingredient is mixed with an inert solid diluent, for example, calcium carbonate, calcium phosphate or kaolin, or as soft gelatin capsules wherein the active ingredients is mixed with water or miscible solvents such as propylene glycol, PEGs and ethanol, or an oil medium, for example peanut oil, liquid paraffin, or olive oil.

Aqueous suspensions contain the active material in admixture with excipients suitable for the manufacture of aqueous suspensions. Oily suspensions may be formulated by suspending the active ingredient in a vegetable oil, for example arachis oil, olive oil, sesame oil or coconut oil, or in mineral oil such as liquid paraffin. The oily suspensions may contain a thickening agent, for example beeswax, hard paraffin or cetyl alcohol. Sweetening agents and flavoring agents may be added to provide a palatable oral preparation. These compositions may be preserved by the addition of an anti-oxidant such as ascorbic acid. Syrups and elixirs may be formulated with sweetening agents, for example glycerol, propylene glycol, sorbitol or sucrose.

The instant invention also encompasses a process for preparing a pharmaceutical composition comprising combining a compound of Formula I with a pharmaceutically acceptable carrier. Also encompassed is the pharmaceutical composition which is made by combining a compound of Formula I with a pharmaceutically acceptable carrier. The carrier is comprised of one or more pharmaceutically acceptable excipients. Furthermore, a therapeutically effective amount of a compound of this invention can be used for the preparation of a medicament useful for inhibiting aldosterone synthase, inhibiting CYP11B2, for normalizing a disturbed aldosterone balance, or for treating or preventing any of the medical conditions described herein, in dosage amounts described herein.

The amount of active compound of Formula I and its pharmaceutically acceptable salts in the pharmaceutical composition may be, for example but not limited to, from 0.1 to 200 mg, preferably from 0.1 to 50 mg, per dose on a free acid/free base weight basis, but depending on the type of the pharmaceutical composition and potency of the active ingredient it could also be lower or higher. Pharmaceutical compositions usually comprise 0.5 to 90 percent by weight of the active compound on a free acid/free base weight basis.

Since the compounds of Formula I inhibit aldosterone synthase, apart from use as pharmaceutically active compounds in human medicine and veterinary medicine, they can also be employed as a scientific tool or as aid for biochemical investigations in which such an effect on aldosterone synthase and aldosterone levels is intended, and also for diagnostic purposes, for example in the in vitro diagnosis of cell samples or tissue samples. The compounds of Formula I can also be employed as intermediates for the preparation of other pharmaceutically active compounds.

One or more additional pharmacologically active agents (or therapeutic agents) may be administered in combination with a compound of Formula I. An additional active agent (or agents) is intended to mean a pharmaceutically active agent (or agents) different from the compound of Formula I. Generally, any suitable additional active agent or agents, including but not limited to anti-hypertensive agents, anti-atherosclerotic agents such as a lipid modifying compound, anti-diabetic agents and/or anti-obesity agents may be used in any combination with the compound of Formula I in a single dosage formulation (a fixed dose drug combination), or may be administered to the patient in one or more separate dosage formulations which allows for concurrent or sequential administration of the active agents (co-administration of the separate active agents). Examples of additional active agents which may be employed include but are not limited to angiotensin converting enzyme (ACE) inhibitors (e.g, alacepril, benazepril, captopril, ceronapril, cilazapril, delapril, enalapril, enalaprilat, fosinopril, imidapril, lisinopril, moexepril, moveltipril, perindopril, quinapril, ramipril, spirapril, temocapril, or trandolapril); dual inhibitors of angiotensin converting enzyme (ACE) and neutral endopeptidase (NEP) such as omapatrilat, sampatrilat and fasidotril; angiotensin II receptor antagonists (e.g., candesartan, eprosartan, irbesartan, losartan, olmesartan, telmisartan, valsartan) neutral endopeptidase inhibitors (e.g., thiorphan and phosphoramidon), aldosterone antagonists, renin inhibitors (e.g., enalkrein, RO 42-5892, A 65317, CP 80794, ES 1005, ES 8891, SQ 34017, aliskiren (2(S),4(S),5(S),7(S)—N-(2-carbamoyl-2-methylpropyl)-5-amino-4-hydroxy-2,7-diisopropyl-8-[4-methoxy-3-(3-methoxypropoxy)-phenyl]-octanamid hemifumarate) SPP600, SPP630 and SPP635), endothelin receptor antagonists, vasodilators, calcium channel blockers (e.g., amlodipine, bepridil, diltiazem, felodipine, gallopamil, nicardipine, nifedipine, niludipine, nimodipine, nisoldipine veraparmil), potassium channel activators (e.g., nicorandil, pinacidil, cromakalim, minoxidil, aprilkalim, loprazolam), diuretics (e.g., hydrochlorothiazide) including loop diuretics such as ethacrynic acid, furosemide, bumetanide and torsemide, sympatholitics, beta-adrenergic blocking drugs (e.g., acebutolol, atenolol, betaxolol, bisoprolol, carvedilol, metoprolol, metoprolol tartate, nadolol, propranolol, sotalol, timolol); alpha adrenergic blocking drugs (e.g., doxazocin, prazocin or alpha methyldopa) central alpha adrenergic agonists, peripheral vasodilators (e.g. hydralazine); lipid lowering agents (e.g., simvastatin and lovastatin which are marketed as ZOCOR® and MEVACOR® in lactone pro-drug form and function as inhibitors after administration, and pharmaceutically acceptable salts of dihydroxy open ring acid HMG-CoA reductase inhibitors such as atorvastatin (particularly the calcium salt sold in LIPITOR®), rosuvastatin (particularly the calcium salt sold in CRESTOR®), pravastatin (particularly the sodium salt sold in PRAVACHOL®), and fluvastatin (particularly the sodium salt sold in LESCOL®); a cholesterol absorption inhibitor such as ezetimibe (ZETIA®), and ezetimibe in combination with any other lipid lowering agents such as the HMG-CoA reductase inhibitors noted above and particularly with simvastatin (VYTORIN®) or with atorvastatin calcium); niacin in immediate-release or controlled release forms, and particularly in niacin in combination with a DP antagonist such as laropiprant (TREDAPTIVE®) and/or with an HMG-CoA reductase inhibitor; niacin receptor agonists such as acipimox and acifran, as well as niacin receptor partial agonists; metabolic altering agents including insulin sensitizing agents and related compounds (e.g., muraglitazar, glipizide, metformin, rosiglitazone), dipeptidyl peptidase 4 inhibitors (e.g., sitagliptin, alogliptin, vildagliptin, saxagliptin, linagliptin, dutogliptin, gemigliptin); or with other drugs beneficial for the prevention or the treatment of the above-mentioned diseases including nitroprusside and diazoxide.

In general, the compounds in the invention may be produced by a variety of processes know to those skilled in the art and by know processes analogous thereto. The invention disclosed herein is exemplified by the following preparations and examples which should not be construed to limit the scope of the disclosure. Alternative mechanistic pathways and analogous structures will be apparent to those skilled in the art. The practitioner is not limited to these methods and one skilled in the art would have resources such as Chemical Abstracts or Beilstein at his or her disposal to assist in devising an alternative method of preparing a specific compound.

The compounds of the present invention can be prepared according to the procedures of the following Schemes using appropriate materials and are further exemplified by the specific Examples which follow. Moreover, by utilizing the procedures described herein, one of ordinary skill in the art can readily prepare additional compounds of the present invention claimed herein.

Throughout the synthetic schemes, abbreviations are used with the following meanings unless otherwise indicated:

AcCN=acetonitrile; aq=aqueous, Ar=aryl; BSA=bovine serum albumin; Bu=butyl, t-Bu=tert-butyl; n-BuLi=n-butyllithium; conc, conc.=concentrated; c-Pr=cyclopropyl; Cy=cyclohexyl; dba=dibenzylideneacetone; DCM=dichloromethane; DMEM=Dulbecco's modified eagle medium; DMF=N,N-dimethylformamide; DMSO=dimethylsulfoxide; eq.=equivalent(s); EDAC=N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride; EDTA=ethylenediaminetetraacetic acid; Et=ethyl; EtOAc=ethyl acetate; EtOH=ethanol; FBS=Fetal Bovine Serum; h, hr=hour; HPLC=High pressure liquid chromatography; HTRF=homogenous time resolved fluorescence; i-PrOH=isopropanol; i-Pr=isopropyl; LCMS=liquid chromatography-mass spectroscopy; Me=methyl; MeOH=methanol; min, min.=minute; MS=mass spectroscopy; NBS=N-bromosuccinimide; NCS=N-chlorosuccinimide; NMR=nuclear magnetic resonance; PBS=phosphate buffered saline; PdCl₂(dppf)=dichloro[1,1′-bis(diphenylphosphino) ferrocene]palladium(II); Pd₂(dba)₃=tris(dibenzylidineacetone)dipalladium; Pd/C=palladium on activated carbon; Ph=phenyl; Pr=propyl; Py=pyridyl; PyBOP=(benzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate; OAc=acetate; OTf=trifluoromethanesulfonate; RT, rt=room temperature; sat.=saturated; S-Phos=2-dichlorocyclohexylphosphino-2′,6′-dimethoxybiphenyl; TBAF=tetrabutylammonium fluoride; TBDMS=tert-butyldimethylsilyl; THF=tetrahydrofuran; triflate, and TfO₂=trifluoromethanesulfonic anhydride.

As will be known to those skilled in the art, in all schemes, the products of Formula I and all synthetic intermediates may be purified from unwanted side products, reagents and solvents by recrystallization, trituration, preparative thin layer chromatography, flash chromatography on silica gel as described by W. C. Still et al, J. Org. Chem. 1978, 43, 2923, or reverse-phase HPLC. Compounds purified by HPLC may be isolated as the corresponding salt.

Additionally, in some instances the final compounds of Formula I and synthetic intermediates may be comprised of a mixture of cis and trans isomers, enantiomers or diastereomers. As will be known to those skilled in the art, such cis and trans isomers, enantiomers and diastereomers may be separated by various methods including crystallization, chromatography using a homochiral stationary phase and, in the case of cis/trans isomers and diastereomers, normal-phase and reverse-phase chromatography.

Chemical reactions were monitored by LCMS, and the purity and identity of the reaction products were assayed by LCMS (electrospray ionization) and NMR. LCMS spectra were recorded on an Agilent 1100 series instrument equipped with an Xterra MS C18 column (3.5 μM, 3.0×50 mm i.d.) and UV detector. ¹H NMR spectra were recorded on a Varian 500 HHz spectrometer unless otherwise noted, and are internally referenced to residual protio solvent signals. Data for ¹H NMR are reported with chemical shift (8 ppm), multiplicity (s=singlet, d=doublet, t=triplet, q=quartet, m=multiplet, br s=broad singlet, br m=broad multiplet), coupling constant (Hz), and integration. Unless otherwise noted, all LCMS ions listed are [M+H]. All temperatures are degrees Celsius unless otherwise noted.

In the Examples, some intermediates and final compounds having a chiral carbon were prepared as racemates, and some chiral intermediates were resolved and the enantiomers were used separately to synthesize enantiomeric downstream intermediates and final products. In some cases racemic final products may have been resolved. In the instances where chiral compounds were separated by chiral HPLC purification, the term “enantiomer A” or “ent A” refers to the first eluting enantiomer and the downstream compounds derived from this enantiomer. The term “enantiomer B” or “ent B” refers to the second eluting enantiomer and the downstream compounds derived from this enantiomer. The term “rac” refers to a racemic mixture. As a result, the chemical nomenclature may indicate that an S and/or an R enantiomer was obtained, but the absolute stereochemistry of the separate enantiomers A and/or B was not determined.

Preparative HPLC was performed using a SunFire Prep C18 OBD column (5 μM, 19×100 mm i.d.) on Gilson instruments equipped with UV detectors.

Flash chromatography on silica gel was performed using pre-packed silica gel columns on Biotage Horizon or Biotage SP-1 instruments equipped with UV detectors.

The following examples are provided so that the invention might be more fully understood. They should neither be construed as forming the only genus that is considered as the invention nor limiting the invention in any way.

##STR00018##
2-Heteroaryl imidazo[1,2-a]pyridines can be synthesized according to the procedure outlined in Scheme 1. 2-Aminopyridines such as 1 are available commercially, are known in the literature or may be synthesized by a variety of procedures by those skilled in the art. Upon heating in the presence of a dehydrating agent such as TiCl₄, and a base such as triethylamine, 2-aminopyridines 1 may undergo cyclization with 3-bromoacetylpyridines such as 2 to afford 2-heteroaryl imidazo[1,2-a]pyridines such as 3.

##STR00019##

2-Heteroaryl imidazo[1,2-a]pyridines can alternatively be synthesized according by the method outlined in Scheme 2. 2-Aminopyridine 1 may be treated with ethyl bromoacetate to afford 2-imino pyridyl acetic acid ester 4, which may then be converted to 2-chloro imidazo[1,2-a]pyridine 5 upon heating in the presence of an activating agent such as oxyphosphorous chloride. Treatment of 3 with an iodinating agent such as N-iodosuccinimide may then afford 2-chloro-3-iodo imidazo[1,2-a]pyridine 6. Boronate acids and esters may be obtained commercially, are known in the literature or may be prepared by a variety of methods by those skilled in the art. Suzuki coupling of iodide 6 with a boronic acid or ester in the presence of a catalyst such as palladium acetate, a ligand such as triphenylphosphine, and a base such as cesium carbonate at elevated temperature may afford coupled product 7. A subsequent Suzuki coupling between 7 and a heteroaryl boronic acid or ester in the presence of a catalyst such as palladium acetate, a ligand such as 2-dicyclohexylphosphino-2′,6′-dimethoxy-1,1′-biphenyl, and a base such as potassium phosphate tribasic may then afford 2-heteroaryl imidazo[1,2-a]pyridine compound 8.

##STR00020## ##STR00021##

2-(Pyridin-3-yl)-5,6-dihydroimidazo[1,2-c]pyrimidin-7(8H)-ones 17 can be synthesized according to the method shown in Scheme 3. 4-Substituted imidazole 9 may be treated with a base such as sodium hydride followed by an electrophile such as a tert-butylsilyldimethylsilyl-protected bromoalkane to afford the alkylated imidazole 10 and its regioisomer. The correct regioisomer 10 may be brominated with a reagent such as N-br omosuccinimide to give the bromoimidazole 11, which upon Suzuki coupling with a boronic acid or ester can then yield imidazolylpyridine 12. Subsequent bromination with N-bromosuccinimide, followed by amination with an amine in the presence of silver triflate can then afford the imidazolylpyridine 14. Deprotection of 14 with a reagent such as tetrabutylammonium fluoride affords the alcohol 15. Oxidation of 15 with an appropriate oxidizing system, such as ruthenium chloride/sodium periodate, may afford the carboxylic acid 16, and with the addition of the coupling reagent EDAC, 16 may be converted to the desired 2-(pyridin-3-yl)-5,6-dihydroimidazo[1,2-c]pyrimidin-7(8H)-ones 17.

Pyridyl boronate esters may be obtained commercially, are known in the literature or may be prepared by a variety of methods by those skilled in the art. One such method, shown in Scheme 4, begins with treatment of 3,5-dibromopyridine 18 with n-butyllithium and acetone in a solvent such as toluene at low temperature to provide 19. Heating of bromide 19 and 4,4,4′,4′,5,5,5′,5′-octamethyl-2,2′-bi-1,3,2-dioxaborolane in the presence of a catalyst such as dichloro[1,1′-bis(diphenylphosphino)ferrocene]palladium (II) and a base such as potassium acetate in a solvent such as 1,4-dioxane then affords boronate ester 20.

##STR00022##

An alternative method for the preparation of pyridyl boronic acids, shown in Scheme 5, begins with treatment of 1-(5-bromopyridin-3-yl)ethanone 21 with (trifluoromethyl)trimethylsilane and tetrabutylammonium fluoride in a solvent such as tetrahydrofuran to provide 22. Heating of bromide 22 and 4,4,4′,4′,5,5,5′,5′-octamethyl-2,2′-bi-1,3,2-dioxaborolane in the presence of a catalyst such as tris(dibenzylideneacetone)dipalladium (0), a ligand such as tricyclohexylphosphine, and a base such as potassium acetate in a solvent such as 1,4-dioxane then affords boronic acid 23.

##STR00023##

As will be known to those skilled in the art, in all schemes, the products of Formula I and all synthetic intermediates may be purified from unwanted side products, reagents and solvents by recrystallisation, trituration, preparative TLC, flash chromatography on silica gel or reverse-phase HPLC. Compounds purified by HPLC may be isolated as the corresponding salt.

Example 1

##STR00024##

Step A. 6-Fluoro-2-(pyridin-3-yl)imidazo[1,2-a]pyridine

##STR00025##

2-Amino-5-fluoropyridine (0.048 g, 0.427 mmol), 3-bromoacetylpyridine hydrobromide (0.10 g, 0.356 mmol) and chloroform (3.56 mL) were added to a microwave vial. To the resulting solution were added a solution of TiCl₄ in dichloromethane (1.0 M, 0.267 mL, 0.267 mmol) and triethylamine (0.030 mL, 0.214 mmol). The reaction was then heated in a microwave at 110° C. for 30 minutes. The resulting mixture was poured into aqueous sodium hydroxide solution (1.0 N) and extracted with ethyl acetate. The organic extracts were combined, dried over MgSO₄, filtered and concentrated under reduced pressure. Purification by flash chromatography on silica gel (50% to 100% ethyl acetate in hexanes) provided the title compound: LCMS m/z 214.09 [M+H]⁺; ¹H NMR (500 MHz, CDCl₃) δ 9.13 (d, J=1.7 Hz, 1H), 8.59-8.58 (m, 1H), 8.29-8.28 (m, 1H), 8.10 (t, J=2.9, 2.9 Hz, 1H), 7.95 (s, 1H), 7.63 (dd, J=9.9, 5.1 Hz, 1H), 7.40 (dd, J=7.9, 5.0 Hz, 1H), 7.18-7.14 (m, 1H).

Example 2

##STR00026##

Step A. Ethyl 2-(5-fluoro-2-iminopyridin-1(2H)-yl)acetate

##STR00027##

To 2-amino-5-fluoro pyridine (2.0 g, 17.84 mmol) was added ethyl bromoacetate (6.92 mL, 62.4 mmol). The resulting mixture was stirred at room temperature for 18 hours, then filtered. The solids were collected, washed with dichloromethane, and dried under reduced pressure to afford the title compound: LCMS m/z 199.00 [M+H]⁺; ¹H NMR (500 MHz, CD₃OD) δ 8.05 (s, 1H), 7.93-7.90 (m, 1H), 7.14-7.12 (m, 1H), 5.02 (s, 2H), 4.25 (t, J=7.1 Hz, 2H), 1.27 (q, J=7.1 Hz, 3H).

Step B. 2-Chloro-6-fluoroimidazo[1,2-a]pyridine

##STR00028##

A mixture of ethyl 2-imino-5-fluoro-1,2-dihydropyridine-1-yl-acetate hydrobromide (4.12 g, 14.76 mmol) in phosphorus oxychloride (68.8 mL, 738 mmol) was heated at 105° C. for 2 hours. The mixture was then cooled to room temperature and concentrated under reduced pressure. To the resulting residue were added ice water and ammonium hydroxide until the pH of the solution was 8. The solution was then extracted with dichloromethane. The organic extracts were combined, dried over MgSO4, filtered and concentrated under reduced pressure. Purification by flash chromatography on silica gel (30% ethyl acetate in hexanes) provided the title compound: LCMS m/z 170.96 [M+H]⁺, 172.79 [M+2+H]⁺; ¹H NMR (500 MHz, CDCl₃) δ 8.00 (s, 1H), 7.53-7.50 (m, 2H), 7.18-7.13 (m, 1H).

Step C. 2-(5-Bromopyridin-3-yl)propan-2-ol

##STR00029##

To a cooled (−78° C.) solution of 3-acetyl-5-bromo pyridine (1.98 g, 9.90 mmol) in tetrahydrofuran (33 mL) was added dropwise a solution of methyl magnesium bromide in diethyl ether (3.0 M, 6.60 mL, 19.8 mmol). The reaction was warmed to room temperature, and the resulting mixture was stirred at room temperature overnight. The reaction was then quenched with saturated aqueous ammonium chloride solution and extracted with diethyl ether. The organic extracts were combined, washed with brine, dried over magnesium sulfate, filtered and concentrated. Purification by flash chromatography on silica gel (0-60% ethyl acetate in hexanes) provided the title compound: LCMS m/z 217.83 [M+11]⁺; ¹H NMR (500 MHz, CDCl₃) δ 8.61 (s, 1H), 8.53 (s, 1H), 8.01 (d, J=1.9 Hz, 1H), 2.38 (br s, 1H), 1.61 (6H).

Step D. 2-[5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-3-pyridinyl]-2-propanol

##STR00030##

To a 5000-mL 4-necked round-bottom flask purged and maintained with an inert atmosphere of nitrogen were added a solution of the title compound from Example 2 Step C (160 g, 395 mmol) in 1,4-dioxane (2000 mL), 4,4,5,5-tetramethyl-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1,3,2-dioxaborolane (240 g, 498 mmol), potassium acetate (240 g, 1.63 mol), and PdCl₂(dppf) (30 g, 23 mmol). The resulting solution was stirred for 4 hours at 80° C. The reaction was then cooled to room temperature, filtered and concentrated under reduced pressure. The residual solution was diluted with hexanes and filtered. HCl gas was bubbled through the filtrate. The resulting mixture was filtered, and the solids diluted with dichloromethane, then concentrated under reduced pressure. The residue was diluted with H₂O, and washed sequentially with diethyl ether, dichloromethane, and hexanes. The aqueous layer was adjusted to pH 7-8 with saturated aqueous sodium carbonate solution, then extracted with dichlormethane. The organic extracts were combined, dried and concentrated under vacuum to afford the title compound: ¹H NMR (400 MHz, CDCl₃): δ 8.83 (s, 1H), 8.19 (s, 1H), 1.62 (s, 6H), 1.36 (s, 12H).

Step E. 2-(5-(6-Fluoroimidazo[1,2-a]pyridin-2-yl)pyridin-3-yl)propan-2-ol

##STR00031##

To a solution of the title compound from Example 2 Step D (0.1855 g, 0.704 mmol) and the title compound from Example 2 Step B (0.10 g, 0.586 mmol) in tetrahydrofuran (5.86 mL) were added palladium acetate (0.013 g, 0.059 mmol), 2-dicyclohexylphosphino-2′,6′-dimethoxy-1,1′-biphenyl (0.048 g, 0.117 mmol), and potassium phosphate tribasic (0.373 g, 1.759 mmol). The resulting mixture was heated at 100° C. for 18 hours. The mixture was then cooled to room temperature, filtered with the aid of ethyl acetate, and concentrated under reduced pressure. Purification by flash chromatography on silica gel (30-50% acetone in dichloromethane) provided the title compound: LCMS m/z 273.99 [M+H]⁺; ¹H NMR (500 MHz, CDCl₃) δ 8.99 (d, J=1.6 Hz, 1H), 8.72 (d, J=2.2 Hz, 1H), 8.39 (t, J=2.0 Hz, 1H), 8.10 (t, J=2.6 Hz, 1H), 7.96 (s, 1H), 7.63 (dd, J=9.9, 4.8 Hz, 1H), 7.17-7.13 (m, 1H), 2.00 (br s, 1H), 1.68 (s, 6H).

Step F. 2-(5-(3-Chloro-6-fluoroimidazo[1,2-a]pyridin-2-yl)pyridin-3-yl)propan-2-ol

##STR00032##

To a solution of the title compound from Example 2 Step E (0.068 g, 0.251 mmol) in acetonitrile (1.25 ml) was added N-chlorosuccinimide (0.040 g, 0.301 mmol). The resulting mixture was stirred at room temperature for 2 hours, then concentrated under reduced pressure. The resulting residue was diluted with dichloromethane, washed with saturated aqueous sodium chloride solution, dried over MgSO₄, filtered, and concentrated under reduced pressure. Purification by flash chromatography on silica gel (100% ethyl acetate) provided the title compound: LCMS m/z 306.08 [M+H]⁺; ¹H NMR (500 MHz, CDCl₃) 9.23 (d, J=1.7 Hz, 1H), 8.78 (d, J=2.1 Hz, 1H), 8.51 (t, J=2.0 Hz, 1H), 8.08 (t, J=2.5 Hz, 1H), 7.65 (dd, J=9.3, 4.9 Hz, 1H), 7.24-7.20 (m, 1H), 2.02 (br s, 1H), 1.69 (s, 6H).

Example 3

##STR00033##

Step A. 2-Chloro-6-fluoro-3-iodoimidazo[1,2-a]pyridine

##STR00034##

To a solution of the title compound from Example 2 Step B (1.0 g, 5.86 mmol) in acetonitrile (29.3 mL) was added N-iodosuccinimide (1.583 g, 7.04 mmol). The resulting mixture was stirred at room temperature for 2 hours, then concentrated under reduced pressure. The resulting residue was diluted with dichloromethane, washed with saturated aqueous sodium chloride solution, dried over MgSO₄, filtered, and concentrated under reduced pressure. Purification by flash chromatography on silica gel (10-30% ethyl acetate in hexanes) provided the title compound: LCMS m/z 296.70 [M+H]⁺, 298.65 [M+2+H]⁺; ¹H NMR (500 MHz, CDCl₃) δ 8.03 (t, J=2.8 Hz, 1H), 7.56-7.51 (m, 1H), 7.22-7.18 (m, 1H).

Step B. 2-Chloro-6-fluoro-3-methylimidazo[1,2-a]pyridine

##STR00035##

A mixture of the title compound from Example 3 Step A (0.500 g, 1.69 mmol), palladium acetate (0.038 g, 0.169 mmol), methyl boronic acid (0.202 g, 3.37 mmol), cesium carbonate (1.65 g, 5.06 mmol) and triphenyl phosphine (0.088 g, 0.337 mmol) in tetrahydrofuran (8.43 mL) was heated in a sealed tube at 100° C. for 18 hours. The mixture was then cooled to room temperature, filtered, and concentrated under reduced pressure. Purification by flash chromatography on silica gel (0-20% ethyl acetate in hexanes) provided the title compound: LCMS m/z 184.9 [M+H]⁺ 186.86 [M+2+H]⁺; ¹H NMR (500 MHz, CDCl₃) δ 7.75 (d, J=2.4 Hz, 1H), 7.51 (dd, J=9.7, 4.9 Hz, 1H), 7.14-7.102 (m, 1H), 2.44 (s, 3H).

Step C. 2-(5-(6-Fluoro-3-methylimidazo[1,2-a]pyridin-2-yl)pyridin-3-yl)propan-2-ol

##STR00036##

To a solution of the title compound from Example 2 Step D (0.135 g, 0.514 mmol) and the title compound from Example 3 Step B (0.079 g, 0.428 mmol) in tetrahydrofuran (4.28 mL) were added palladium acetate (9.61 mg, 0.043 mmol), 2-dicyclohexylphosphino-2′,6′-dimethoxy-1,1′-biphenyl (0.035 g, 0.086 mmol), and potassium phosphate tribasic (0.273 g, 1.284 mmol). The resulting mixture was heated at 100° C. for 18 hours, then filtered with the aid of ethyl acetate and concentrated under reduced pressure. Purification by flash chromatography on silica gel (50% acetone in dichloromethane) provided the title compound: LCMS m/z 286.17 [M+H]⁺; ¹H NMR (500 MHz, CDCl₃) δ 8.83 (s, 1H), 8.75 (s, 1H), 8.26 (d, J=2.0 Hz, 1H), 7.85 (s, 1H), 7.63 (dd, J=9.8, 5.1 Hz, 1H), 7.16-7.12 (m, 1H), 2.64 (s, 3H), 2.28 (br s, 1H), 1.67 (s, 6H).

Example 4

##STR00037##

Step A. 2-Chloro-6-fluoroimidazo[1,2-a]pyridine-3-carbonitrile

##STR00038##

To a cooled −78° C. solution of the title compound from Example 3 Step A (0.30 g, 1.01 mmol) in tetrahydrofuran (5.06 ml) was added a solution of n-butyllithium in hexanes (1.6 M, 0.696 ml, 1.11 mmol). After 5 minutes, p-toluenesulfonyl cyanide (0.238 g, 1.32 mmol) was added, and the resulting mixture was allowed to slowly warm to room temperature overnight. The resulting mixture was concentrated under reduced pressure and purified by flash chromatography on silica gel (10-50% ethyl acetate in hexanes) to afford the title compound: LCMS m/z 195.88 [M+H]⁺, 197.86 [M+2+H]⁺; ¹H NMR (500 MHz, CDCl₃) δ 8.25 (d, J=2.4 Hz, 1H), 7.69 (dd, J=9.6, 4.8 Hz, 1H), 7.46-7.42 (m, 1H).

Step B. 6-fluoro-2-(5-(2-hydroxypropan-2-yl)pyridin-3-yl)imidazo[1,2-a]pyridine-3-carbonitrile

##STR00039##

To a solution of the title compound from Example 2 Step D (0.053 g, 0.202 mmol) and the title compound from Example 4 Step A (0.033 g, 0.169 mmol) in tetrahydrofuran (0.84 mL) were added palladium acetate (0.0038 g, 0.017 mmol), 2-dicyclohexylphosphino-2′,6′-dimethoxy-1,1′-biphenyl (0.014 g, 0.034 mmol), and potassium phosphate tribasic (0.107 g, 0.506 mmol). The resulting mixture was heated at 100° C. for 18 hours, then filtered with the aid of ethyl acetate and concentrated under reduced pressure. Purification by flash chromatography on silica gel (80% acetone in hexanes) provided the title compound: LCMS m/z 296.96 [M+11]⁺; ¹H NMR (500 MHz, CDCl₃) δ 9.28 (d, J=1.9 Hz, 1H), 8.87 (d, J=2.0 Hz, 1H), 8.55 (t, J=2.1 Hz, 1H), 8.35 (s, 1H), 7.79 (dd, J=9.8, 4.7 Hz, 1H), 7.45-7.41 (m, 1H), 1.98 (br s, 1H), 1.69 (s, 6H).

##STR00040##

Step A. 2-(5-bromopyridin-3-yl)-1,1,1-trifluoropropan-2-ol

To a flask containing 3-acetyl-5-bromopyridine (2.27 g, 11.4 mmol) was added a solution of (trifluoromethyl)trimethylsilane in tetrahydrofuran (0.5 M, 40 mL, 20 mmol) at 0° C. A solution of tetrabutylammonium fluoride in tetrahydrofuran (1.0 M, 11.4 mL, 11.4 mmol) was then added, and the reaction stirred at room temperature until the reaction was complete. The reaction was then concentrated under reduced pressure, diluted with ethyl acetate, and washed with water and saturated aqueous sodium bicarbonate solution. The organic layer was separated, dried over sodium sulfate, filtered and concentrated to give a residue that was purified by flash chromatography on silica gel (10-50% ethyl acetate in hexanes) to provide the racemic title compound: LCMS m/z 269.85 [M+2+H]⁺; ¹H NMR (500 MHz, CD₃OD) δ 8.70 (s, 1H), 8.65 (1H), 8.13 (s, 1H), 1.81 (s, 3H). The racemic title compound was resolved by supercritical fluid chromatography on a chiral AD column, eluting with 10% ethanol:CO₂. Data for enantiomer A: LCMS m/z 271.85 [M+H]⁺; ¹H NMR (500 MHz, CDCl₃) 8.71 (s, 1H), 8.68 (d, J=2.0 Hz, 1H), 8.10 (s, 1H), 1.82 (s, 3H). Data for enantiomer B: LCMS m/z 271.83 [M+H]⁺; ¹H NMR (500 MHz, CDCl₃) 8.71 (s, 1H), 8.68 (s, 1H), 8.10 (s, 1H), 1.81 (s, 3H).

##STR00041##

Step B. [5-(1,1,1-trifluoro-2-hydroxypropan-2-yl)pyridin-3-yl]boronic acid

A vial containing the title compound from Intermediate 2 Step A [enantiomer B (0.647 g, 2.40 mmol)], bis(pinacolato)diboron (1.22 g, 4.79 mmol), tris(dibenzylideneacetone)dipalladium (0) (0.439 g, 0.479 mmol), tricyclohexylphosphine (0.269 g, 0.958 mmol) and potassium acetate (0.705 g, 7.19 mmol) in 1,4-dioxane (12 mL) was flushed with nitrogen, sealed tightly and heated to 80° C. overnight. The reaction was then passed through a syringe filter and concentrated under reduced pressure to provide the title compound: LCMS m/z 235.95 [M+H]⁺.

The compounds in Table 1 were all prepared using chemistry described in the preparation of Examples 14 and Intermediate 1.

TABLE 1
Example	Structure	Name	LCMS
5	##STR00042##	6-fluoro-2-(pyridin-3 - yl)imidazo[1,2-a]pyridine	214.1
6	##STR00043##	6-fluoro-2-(4-methylpyridin-3- yl)imidazo[1,2-a]pyridine	228.0
7	##STR00044##	6-fluoro-2-(5-methylpyridin-3- yl)imidazo[1,2-a]pyridine	228.0
8	##STR00045##	2-(5-(6-fluoroimidazo[1,2- a]pyridin-2-yl)pyridin-3- yl)propan-2-ol	274.0
9	##STR00046##	1,1,1-trifluoro-2-(5-(6- fluoroimidazo[1,2-a]pyridin-2- yl)pyridin-3-yl)propan-2-ol	326.0
10	##STR00047##	8-fluoro-2-(5-methylpyridin-3- yl)imidazo[1,2-a]pyridine	228.0
11	##STR00048##	6-chloro-2-(5-fluoropyridin-3- yl)imidazo[1,2-a]pyridine	248.1
12	##STR00049##	6-chloro-7-fluoro-2-(5- fluoropyridin-3-yl)imidazo[1,2- a]pyridine	266.1
13	##STR00050##	2-(isoquinolin-4-yl)imidazo[1,2- a]pyridine-7-carbonitrile	271.0
14	##STR00051##	6-methyl-2-(6-methylpyridin-3- yl)-3-methylimidazo[1,2- a]pyridine	238.0
15	##STR00052##	8-methyl-2-(6-methylpyridin-3- yl)-3-methylimidazo[1,2- a]pyridine	238.0
16	##STR00053##	7-methyl-2-(6-methylpyridin-3- yl)-3-methylimidazo[1,2- a]pyridine	238.0
17	##STR00054##	6-fluoro-3-methyl-2-(pyridin-3- yl)imidazo[1,2-a]pyridine	228.2
18	##STR00055##	6-fluoro-3-methyl-2-(5- methoxypyridine-3- yl)imidazo[1,2-a]pyridine	258.0
19	##STR00056##	6-fluoro-3-methyl-2-(5- methylpyridin-3-yl)imidazo[1,2- a]pyridine	242.0
20	##STR00057##	6-fluoro-3-methyl-2-(4- methylpyridin-3-yl)imidazo[1,2- a]pyridine	242.0
21	##STR00058##	5-(6-fluoro-3- methylimidazo[1,2-a]pyridin-2- yl)nicotinonitrile	253.0
22	##STR00059##	3-methyl-6-fluoro-2-(5- (trifluoromethyl)pyridin-3- yl)imidazo[1,2-a]pyridine	296.0
23	##STR00060##	2-(5-(6-fluoro-3- methylimidazo[1,2-a]pyridin-2- yl)pyridin-3-yl)propan-2-ol	286.2
24	##STR00061##	1,1,1-trifluoro-2-(5-(6-fluoro-3- methylimidazo[1,2-a]pyridin-2- yl)pyridin-3-yl)propan-2-ol	340.0
25	##STR00062##	4-(6-fluoro-3-ethylimidazo[1,2- a]pyridin-2-yl)isoquinoline	278.2
26	##STR00063##	7-fluoro-2-(5-fluoropyridin-3- yl)-3-methylimidazo[1,2- a]pyridine	246.0
27	##STR00064##	3-cyclopropyl-6-methyl-2-(4- methylpyridin-3-yl)imidazo[1,2- a]pyridine	264.2
28	##STR00065##	3-cyclopropyl-6-fluoro-2- (pyridin-3-yl)imidazo[1,2- a]pyridine	254.0
29	##STR00066##	3-cyclopropyl-6-fluoro-2-(5- methylpyridin-3-yl)imidazo[1,2- a]pyridine	268.2
30	##STR00067##	3-cyclopropyl-6-fluoro-2-(6- methylpyridin-3-yl)imidazo[1,2- a]pyridine	268.2
31	##STR00068##	3-cyclopropyl-6-fluoro-2-(5- fluoropyridin-3-yl)imidazo[1,2- a]pyridine	272.0
32	##STR00069##	3-cyclopropyl-6-fluoro-2-(5- fluoro-4-methylpyridin-3- yl)imidazo[1,2-a]pyridine	286.2
33	##STR00070##	3-cyclopropyl-2-(4-ethyl-5- fluoropyridin-3-yl)-6- fluoroimidazo[1,2-a]pyridine	300.2
34	##STR00071##	3-cyclopropyl-6-fluoro-2-(5- methoxypyridin-3-yl)imidazo [1,2-a]pyridine	284.0
35	##STR00072##	3-cyclopropyl-6-fluoro-2-(5- (trifluoromethyl)pyridin-3- yl)imidazo[1,2-a]pyridine	322.2
36	##STR00073##	5-(3-cyclopropyl-6- fluoroimidazo[1,2-a]pyridin-2- yl)nicotinonitrile	278.9
37	##STR00074##	2-(5-(3-cyclopropyl-6- fluoroimidazo[1,2-a]pyridin-2- yl)pyridin-3-yl)propan-2-ol	312.0
38	##STR00075##	2-(5-(3-cyclopropyl-6- fluoroimidazo[1,2-a]pyridin-2- yl)pyridin-3-yl)-1,1,1- trifluoropropan-2-ol	366.2
39	##STR00076##	3-cyclopropyl-6-fluoro-2-(5- phenylpyridin-3-yl)imidazo[1,2- a]pyridine	330.0
40	##STR00077##	methyl 5-(3-cyclopropyl-6- fluoroimidazo[1,2-a]pyridin-2- yl)nicotinate	312.0
41	##STR00078##	4-(3-cyclopropyl-6- fluoroimidazo[1,2-a]pyridin-2- yl)isoquinoline	304.2
42	##STR00079##	6-chloro-3-cyclopropyl-2-(5- fluoropyridin-3-yl)imidazo[1,2- a]pyridine	288.1
43	##STR00080##	6-chloro-3-cyclopropyl-7-fluoro- 2-(5-fluoropyridin-3- yl)imidazo[1,2-a]pyridine	306.1
44	##STR00081##	4-(3-cyclopropyl-8- fluoroimidazo[1,2-a]pyridin-2- yl)isoquinoline	264.0
45	##STR00082##	2-{5-[3-cyclopropyl-6- (trifluoromethyI)imidazo[1,2- a]pyridin-2-yl]pyridin-3-yl}- 1,1,1-trifluoropropan-2-ol	416.1
46	##STR00083##	3-cyclopropyl-2-[5-(1,1,1- trifluoro-2-hydroxypropan-2- yl)pyridin-3-yl]imidazo[1,2- a]pyridine-6-carbonitrile	373.1

Assay Description and Results

Methods for V79-Human-CYP11B2 and V79-Human-CYP11B1 Assays:

V79 cell lines stably expressing the either the human CYP11B2 or the human CYP11B1 enzyme were generated using a standard transfection protocol. V79 cells were transfected with plasmids pTriEx3-Hygro-hCyp11B2 or pTriEx3-Hygro-hCyp11B1 using Lipofectamine2000 reagent. V79 cells that stably express the human CYP11B2 or human CYP11B1 enzyme were selected for and maintained in DMEM supplemented with 10% FBS and 400 μg/mL hygromycin for 2 weeks. Single cell clones were generated by infinite dilution in DMEM supplemented with 10% FBS and 400 μg/mL hygromycin until single colonies were obtained. Clones V79-hCYP11B2-CLE9 and V79-hCYP11B1-CL8C7, were determined to produce the most aldosterone and cortisol, respectively, and were selected for inhibitor screening. For testing of inhibitors, cells were harvested at 80% confluency with 0.5% Trypsan-EDTA, washed once in PBS, and reconstituted in DMEM+0.1% BSA media at a cell concentration of 600,000 cells/mL for the CYP11B2 assay and 280,000 cells/mL for the CYP11B1 assay. 25 μL of cells were added to a 384 well tissue culture treated plate and mixed with 0.3 μL of inhibitor or DMSO (1% final DMSO concentration) for 1 hour at 37° C., 5% CO₂. After pre-incubation with inhibitor, the reaction was initiated by adding 5 μL of substrate (final concentration of 125 nM 11-deoxycorticosterone for the CYP11B2 assay or 250 nM 11-deoxycortisol for the CYP11B1 assay). The reaction was carried out for 3 hours at 37° C., 5% CO₂ and was stopped by harvesting the supernatants. The amount of product in the supernatant (aldosterone for CYP11B2 assay and cortisol for the CYP11B1 assay) was measured using HTRF-based assay kit (Aldosterone HTRF-CisBio#64ALDPEB, Cortisol HTRF-CisBio #63IDC002-CORT). IC₅₀s for the inhibitor were determined by plotting the amount of product formed against the concentration of inhibitor using sigmoidal dose-response curve (variable slope) fit in GraphPad.

The compounds of Examples 1-46 were tested in the V79-Human-CYP11B2 cell assay and found to have IC₅₀s for inhibition of human CYP11B2 of less than 10000 nM. A sub-group of compounds had IC₅₀s less than or equal to 250 nM, and a further sub-group of compounds had IC₅₀s less than or equal to 50 nM.

The compounds of Examples 1-46 were also tested in the V79-Human-CYP11B1 cell assay. A sub-group of compounds were at least 10-fold more selective for inhibition of CYP11B2 as compared to CYP11B1, and a further sub-group of compounds were at least 30-fold more selective for inhibition of CYP11B2. Representative examples of data collected for compounds of the present invention are shown in Table 2 below.

TABLE 2
		V79
		Human	V79 Human
		CYP11B2	CYP11B1
Example	IUPAC Name	IC50 (nM)	IC50 (nM)
6	6-fluoro-2-(4-methylpyridin-3-	22.4	63*
	yl)imidazo[1,2-a]pyridine
7	6-fluoro-2-(5-methylpyridin-3-	56.2	60*
	yl)imidazo[1,2-a]pyridine
14	6-methyl-2-(6-methylpyridin-3-	9.1	2399
	yl)-3-methylimidazo[1,2-a]pyridine
15	8-methyl-2-(6-methylpyridin-3-	3.8	646
	yl)-3-methylimidazo[1,2-a]pyridine
16	7-methyl-2-(6-methylpyridin-3-	204	68*
	yl)-3-methylimidazo[1,2-
	a]pyridine
18	6-fluoro-3-methyl-2-(5-	0.3	32.4
	methoxypyridin-3-yl)imidazo[1,
	2-a]pyridine
19	6-fluoro-3-methyl-2-(5-	0.45	40.7
	methylpyridin-3-yl)imidazo[1,2-
	a]pyridine
20	6-fluoro-3-methyl-2-(4-	2.2	135
	methylpyridin-3-yl)imidazo[1,2-
	a]pyridine
25	4-(6-fluoro-3-ethylimidazo[1,2-	0.1	14.8
	a]pyridin-2-yl)isoquinoline
26	7-fluoro-2-(5-fluoropyridin-3-	4.7	912
	yl)-3-methylimidazo[1,2-
	a]pyridine
28	3-cyclopropyl-6-fluoro-2-	23.4	76*
	(pyridin-3-yl)imidazo[1,2-
	a]pyridine
29	3-cyclopropyl-6-fluoro-2-(5-	1.5	589
	methylpyridin-3-yl)imidazo[1,2-
	a]pyridine
30	3-cyclopropyl-6-fluoro-2-(6-	3.2	1072
	methylpyridin-3-yl)imidazo[1,2-
	a]pyridine
31	3-cyclopropyl-6-fluoro-2-(5-	10.7	67*
	fluoropyridin-3-yl)imidazo[1,2-
	a]pyridine
34	3-cyclopropyl-6-fluoro-2-(5-	4.5	759
	methoxypyridin-3-yl)imidazo[1,
	2-a]pyridine
35	3-cyclopropyl-6-fluoro-2-(5-	7.1	1023
	(trifluoromethyl)pyridin-3-
	yl)imidazo[1,2-a]pyridine
38	2-(5-(3-cyclopropyl-6-	6.3	1122
	fluoroimidazo[1,2-a]pyridin-2-
	yl)pyridin-3-yl)-1,1,1-
	trifluoropropan-2-ol
41	4-(3-cyclopropyl-6-	0.5	57.5
	fluoroimidazo[1,2-a]pyridin-2-
	yl)isoquinoline
44	4-(3-cyclopropyl-8-	14.5	2188
	fluoroimidazo[1,2-a]pyridin-2-
	yl)isoquinoline
*= % inhibition at 10 μM

While the invention has been described with reference to certain particular embodiments thereof, numerous alternative embodiments will be apparent to those skilled in the art from the teachings described herein. Recitation or depiction of a specific compound in the claims (i.e., a species) without a specific stereoconfiguration designation, or with such a designation for less than all chiral centers, is intended to encompass the racemate, racemic mixtures, each individual enantiomer, a diastereoisomeric mixture and each individual diastereomer of the compound where such forms are possible due to the presence of one or more asymmetric centers. All patents, patent applications and publications cited herein are incorporated by reference in their entirety.

Claims

1. A compound of the structural formula

2. The compound as defined in claim 1 or a pharmaceutically acceptable salt thereof, which has the structural formula II e####

##STR00086##

wherein:

R² is independently halogen, —CN, alkyl, haloalkyl, cycloalkyl, OR⁷ or phenyl optionally substituted by halogen;

R³ is halogen, —CN, alkyl or cycloalkyl;

R⁴ is H, halogen, —CN, alkyl or cycloalkyl;

R⁵ is:

i.) H, halogen, —CN, alkyl, —OR⁷, haloalkyl or phenyl optionally substituted by halogen or haloalkyl;

ii.) —C(O)OR⁷; or

iii.) a group of the formula:

##STR00087##

where:

R^a is H, OH, or —C₁-C₃-alkyl optionally substituted with 1 to 3 —F;

R^b is H, —OH, or —C₁-C₃-alkyl optionally substituted with 1 to 3 —F;

R^c is —C₁-C₃-alkyl optionally substituted with 1 to 3 —F; —OC₁-C₃-alkyl;

—N(H)S(O)₂—C₁-C₃-alkyl; optionally substituted with 1 to 3 —F; or —N(H)C(O)C₁-C₃-alkyl, optionally substituted with 1 to 3 —F;

R⁷ is H, alkyl, haloalkyl, cycloalkyl, or phenyl optionally substituted by halogen; and

a is 0, 1 or 2.

3. The compound as defined in claim 1 or a pharmaceutically acceptable salt thereof, which has the structural formula e####

##STR00088##

wherein:

R¹ is independently H or alkyl;

R² is independently halogen, —CN, alkyl, haloalkyl, cycloalkyl, OR⁷ or phenyl optionally substituted by halogen;

R³ is H, halogen, —CN, alkyl or cycloalkyl;

R⁴ is H, halogen, —CN, alkyl or cycloalkyl;

R⁵ is:

i.) H, halogen, —CN, alkyl, —OR⁷, —C(O)OR⁷, haloalkyl or phenyl optionally substituted by halogen or haloalkyl; or

ii.) a group of the formula:

##STR00089##

where:

R^a is H, OH, or —C₁-C₃-alkyl optionally substituted with 1 to 3 —F;

R^b is H, —OH, or —C₁-C₃-alkyl optionally substituted with 1 to 3 —F;

R^c is —C₁-C₃-alkyl optionally substituted with 1 to 3 —F; —OC₁-C₃-alkyl;

—N(H)S(O)₂—C₁-C₃-alkyl, optionally substituted with 1 to 3 —F; or —N(H)C(O)C₁-C₃-alkyl, optionally substituted with 1 to 3 —F;

R⁷ is H, alkyl, haloalkyl, cycloalkyl, or phenyl optionally substituted by halogen; and

a is 0, 1 or 2.

4. The compound as defined in claim 1 or a pharmaceutically acceptable salt thereof, which has the structural formula

##STR00090##

wherein:

R² is independently halogen, —CN, alkyl, haloalkyl, cycloalkyl, OR⁷ or phenyl optionally substituted by halogen;

R³ is halogen, —CN, alkyl or cycloalkyl;

R⁶ is alkyl or halo;

a is 0, 1 or 2; and

b is 0, 1 or 2.

5. The compound as defined in claim 1 or a pharmaceutically acceptable salt thereof, which has the structural formula

##STR00091##

wherein:

R² is independently halogen, —CN, alkyl, haloalkyl, cycloalkyl, OR⁷ or phenyl optionally substituted by halogen;

R³ is halogen, —CN, alkyl or cycloalkyl;

R⁶ is alkyl or halo;

a is 0, 1 or 2; and

b is 0, 1 or 2.

6. The compound as defined in claim 1 which is

6-methyl-2-(6-methylpyridin-3-yl)-3-methylimidazo[1,2-a]pyridine;

8-methyl-2-(6-methylpyridin-3-yl)-3-methylimidazo[1,2-a]pyridine;

4-(6-fluoro-3-ethylimidazo[1,2-a]pyridin-2-yl)isoquinoline;

6-fluoro-3-methyl-2-(5-methoxypyridin-3-yl)imidazo[1,2-a]pyridine;

6-fluoro-3-methyl-2-(5-methylpyridin-3-yl)imidazo[1,2-a]pyridine;

7-fluoro-2-(5-fluoropyridin-3-yl)-3-methylimidazo[1,2-a]pyridine;

6-fluoro-3-methyl-2-(4-methylpyridin-3-yl)imidazo[1,2-a]pyridine;

7-methyl-2-(6-methylpyridin-3-yl)-3-methylimidazo[1,2-a]pyridine;

3-cyclopropyl-6-fluoro-2-(5-methylpyridin-3-yl)imidazo[1,2-a]pyridine;

3-cyclopropyl-6-fluoro-2-(6-methylpyridin-3-yl)imidazo[1,2-a]pyridine;

2-(5-(3-cyclopropyl-6-fluoroimidazo[1,2-a]pyridin-2-yl)pyridin-3-yl)-1,1,1-trifluoropropan-2-ol;

3-cyclopropyl-6-fluoro-2-(5-methoxypyridin-3-yl)imidazo[1,2-a]pyridine;

3-cyclopropyl-6-fluoro-2-(5-(trifluoromethyl)pyridin-3-yl)imidazo[1,2-a]pyridine;

4-(3-cyclopropyl-6-fluoroimidazo[1,2-a]pyridin-2-yl)isoquinoline;

3-cyclopropyl-6-fluoro-2-(pyridin-3-yl)imidazo[1,2-a]pyridine;

N-((5-(3-cyclopropyl-6-fluoroimidazo[1,2-a]pyridin-2-yl)pyridin-3-yl)methyl) ethanesulfonamide;

3-cyclopropyl-6-fluoro-2-(5-fluoropyridin-3-yl)imidazo[1,2-a]pyridine;

4-(3-cyclopropyl-8-fluoroimidazo[1,2-a]pyridin-2-yl)isoquinoline;

6-fluoro-2-(4-methylpyridin-3-yl)imidazo[1,2-a]pyridine;

6-fluoro-2-(5-methylpyridin-3-yl)imidazo[1,2-a]pyridine;

or a pharmaceutically acceptable salt thereof.

7. A pharmaceutical composition comprising a therapeutically effective amount of at least one compound of formula I as defined in claim 1 or a pharmaceutically acceptable salt thereof and a pharmaceutically acceptable carrier.

8. A pharmaceutical composition comprising a therapeutically effective amount of at least one compound of formula I as defined in claim 1 or a pharmaceutically acceptable salt thereof, a therapeutically effective amount of at least one additional therapeutic agent and a pharmaceutically acceptable carrier.

9. A method for the treatment of one or more conditions associated with inhibiting CYP11B2, wherein said conditions are selected from hypertension, heart failure, congestive heart failure, diastolic dysfunction, left ventricular diastolic dysfunction, heart failure, diastolic dysfunction, left ventricular diastolic dysfunction, diastolic heart failure, systolic dysfunction, hypokalemia, renal failure, restenosis, syndrome X, nephropathy, post-myocardial infarction, coronary heart diseases, increased formation of collagen, fibrosis and remodeling following hypertension and endothelial, which comprises administering a therapeutically effective amount at least one compound of formula I as defined in claim 1 or a pharmaceutically acceptable salt thereof to a mammal in need of such treatment.