Aldosterone is a key signaling component of the renin-angiotensin-aldosterone system and as such has been shown to contribute to cardiovascular pathology such as hypertension and heart failure. Aldosterone synthase (CYP11B2) is responsible for the final three steps of aldosterone synthesis and thus is a viable therapeutic target. A series of imidazole derived inhibitors, including clinical candidate 7n, have been identified through design and structure−activity relationship studies both in vitro and in vivo. Compound 7n was also found to be a potent inhibitor of 11β-hydroxylase (CYP11B1), which is responsible for cortisol production. Inhibition of CYP11B1 is being evaluated in the clinic for potential treatment of hypercortisol diseases such as Cushing's syndrome. KEYWORDS: Inhibitor, CYP11B2, aldosterone synthase, aldosterone, hypertension, enzyme, CYP11B1, Cushing's syndrome, cortisol O ne of the primary functions of aldosterone through the mineralocorticoid receptor (MR) is to effect retention of sodium and excretion of potassium by the kidney.1 The elevation of aldosterone causes an increase in blood pressure as well as facilitating other cardiac, renal, and vascular damage. Activation of the renin-angiotensin system (RAS) induces aldosterone production. As such, MR antagonists have been used in the treatment of heart failure.2−4 While both RAS inhibitors and MR antagonists have been shown to reduce some of the pathological effects of aldosterone, there are noted drawbacks. In the case of RAS inhibition, a reduction of aldosterone is realized initially; however, this is not maintained. 5,6 Likewise, MR antagonists do not reduce the level of aldosterone, and in fact, they have been shown to induce aldosterone production.7 Thus, it was thought that there would be therapeutic benefit in directly inhibiting aldosterone production.Aldosterone is produced in the zona glomerulosa of the adrenal gland by the enzymatic action of aldosterone synthase (CYP11B2) on deoxycorticosterone. 8,9 Clinical observations suggested that the racemic aromatase (CYP19) inhibitor fadrazole affected aldosterone levels and subsequent preclinical studies demonstrated that the R-enantiomer (FAD286, Figure 1) was a potent inhibitor of CYP11B2.10 From this understanding we embarked on a program to investigate the structure−activity relationship of the FAD286 scaffold and to gain a more extensive understanding of the potential of aldosterone synthase inhibition to treat aldosterone-driven pathologies.Relatively little was known about the impact of substitution at R 1 , although we quickly realized that, as with FAD286, chirality at this point of attachment was important. The impact of altering the size of the saturated ring was not understood at the outset. Preliminary structure−activity relationships (SAR) around the phenyl ring indicated that R 2 would be a most promising site for optimization.In general the compounds from series I (n = 1), series II (n = 2), and series III (n = 3) were prepared as outlined in Scheme 1. Intermed...