Studies on steroids. LXIII. Synthesis of cholesterol analogs with a modified side chain.

Abstract

The Li2CuCl4-catalyzed Grignard reaction of the p-toluenesulfonates of 3β-tetrahydropyranyloxybisnorchol-5-en-22-ol (9) and 3β-tetrahydropyranyloxychol-5-en-24-ol (3) afforded several cholesterol analogs with a modified side chain (10). The reaction of 9 with 3-methyl-2-butenylmagnesium chloride gave a mixture of desmosterol (11) and its allylic isomer (12) in a ratio of 2 : 1. 25-Methylcholesterol (7) was prepared from the cholanal derivative (5) by reaction with t-butylmagnesium bromide followed by deoxygenation of the resulting 24-carbinol 6.