A stereoselective synthesis of the allo-bile acids from the 5β-isomers

The allo-bile acids are a subset of the family of steroidal detergents found in most vertebrates. Because there are no major biological feedstocks for isolation of the allo-bile acids, they must be synthesized from the abundant 5β-reduced isomers. Here we report a general set of methods for the synthesis of allo-bile acids from the corresponding 5-β isomers demarcated by a selective C-3 oxidation, IBX unsaturation, and stereoselective saturation.