Heme Oxygenase Inhibition by 1‐Aryl‐2‐(1H‐imidazol‐1‐yl/1H‐1,2,4‐triazol‐1‐yl)ethanones and Their Derivatives

Previous studies by our research group have been concerned with the design of selective inhibitors of heme oxygenases (HO‐1 and HO‐2). The majority of these were based on a four‐carbon linkage of an azole, usually an imidazole, and an aromatic moiety. In the present study, we designed and synthesized a series of inhibition candidates containing a shorter linkage between these groups, specifically, a series of 1‐aryl‐2‐(1H‐imidazol‐1‐yl/1H‐1,2,4‐triazol‐1‐yl)ethanones and their derivatives. As regards HO‐1 inhibition, the aromatic moieties yielding best results were found to be halogen‐substituted residues such as 3‐bromophenyl, 4‐bromophenyl, and 3,4‐dichlorophenyl, or hydrocarbon residues such as 2‐naphthyl, 4‐biphenyl, 4‐benzylphenyl, and 4‐(2‐phenethyl)phenyl. Among the imidazole‐ketones, five ( 36 – 39 , and 44 ) were found to be very potent (IC₅₀<5 μM ) toward both isozymes. Relative to the imidazole‐ketones, the series of corresponding triazole‐ketones showed four compounds ( 54 , 55 , 61 , and 62 ) having a selectivity index >50 in favor of HO‐1. In the case of the azole‐dioxolanes, two of them ( 80 and 85 ), each possessing a 2‐naphthyl moiety, were found to be particularly potent and selective HO‐1 inhibitors. Three non‐carbonyl analogues ( 87 , 89 , and 91 ) of 1‐(4‐chlorophenyl)‐2‐(1H‐imidazol‐1‐yl)ethanone were found to be good inhibitors of HO‐1. For the first time in our studies, two azole‐based inhibitors ( 37 and 39 ) were found to exhibit a modest selectivity index in favor of HO‐2. The present study has revealed additional candidates based on inhibition of heme oxygenases for potentially useful pharmacological and therapeutic applications.