Potential Bile Acid Metabolites. 5.¹ 12B-Hydroxy Acids by Stereoselective Reduction

Abstract

According to previous research the practical route² to 12β-hydroxycholanic³ acids was by Raney nickel catalytic hydrogenation of the corresponding keto acids, but the method suffers from several disadvantages: (1) the required ratio of catalyst to substrate is inordinately high, (2) the reaction is usually slow, with complete reduction time ranging from 6 hours (12-oxocholanic acid) to 48 hours (certain dihydroxy keto acids), (3) recovery from the adsorbed product from the catalyst is incomplete, and (4) with long reaction times side reactions can occur, as was recently reported^2c that during Raney nickel reduction of methyl 3β, 7α-dihydroxy-12-oxocholanate (1), requiring 48 hours for completion, partial inversion at C-3 took place.