The synthesis of 6-chloro-2-(4-chlorobenzoyl)-1H-indol-3-ylacetic acid (1), a selective cyclooxygenase 2 (COX-2) inhibitor, is described. The synthesis relied on a novel indole formation that involved an alkylation/1,4-addition/elimination/isomerization cascade. It was demonstrated that the entire sequence from sulfonamide 13 and bromoketone 14 to the desired indole (1) could be executed in a single pot.
Divalent tin enolates formed from stannous triflate and ketones react with carbonyl compounds under mild conditions to give the corresponding aldol products in good yields. In the case of cross-coupling with aldehydes, good to excellent erythro-selectivity was observed.
Described herein are structure-activity relationships (SARs) of 4-[5-fluoro-3-[4-(2-methyl-1H-imidazol-1-yl)benzyloxy]-phenyl]-4-methoxy-3,4,5,6-tetrahydro-2H-pyran (1, CJ-12,918), an imidazole 5-lipoxygenase (5-LO) inhibitor. When 1 was tested in preclinical studies, cataract formation was observed in rats; however, this compound was metabolized extensively in vivo and showed low systemic exposure. To eliminate this side effect and enhance bioavailability, structural modification was focused on replacing the methoxy group of 1 by modulating lipophilicity (i.e., predicted log D at pH 7.4). The SARs led to the discovery of 4-[5-fluoro-3-[4-(2-methyl-1H-imidazol-1-yl)benzyloxy]phenyl]-3,4,5,6-tetrahydro-2H-pyran-4-carboxamide (10, CJ-13,454), which was less lipophilic by 1.2 log D units and showed in vivo potency (ED(50) = 4-9 mg/kg) equipotent to 1. Enhanced metabolic stability resulted in fewer in vivo metabolites, as well as improved bioavailability and a better toxicological profile. Thus, 10 was found to be a more practical lead for an orally active 5-LO inhibitor.
Divalent tin enolates, formed from stannous triflate and ketones, react with a second ketone under mild conditions to afford the corresponding cross-aldol products in good to excellent yields. In the case of the cross-coupling with aromatic ketone, enhanced threo-selectivity was observed.
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