Novel azaandrostane derivatives for the synthesis of 17β-(N-tert-butyl carbamoyl)-4-aza-5α-androst-1-ene-3-one

A new industrially viable process for the preparation of 17 beta-(N-tert-butyl carbamoyl)-4-aza-5 alpha-androst-1-ene-3-one, also known by the generic name finasteride (6) from the new azaandrostane derivatives such as 17 beta-(N-tert-butyl carbamoyl)-4-benzoyl-4-aza-5 alpha-andro stane-3-one (4), 17 beta-(N-tert-butyl carbamoyl)-4-benzoyl-4-aza-5 alpha-androst-1-ene-3-one (5) is reported. In this process, benzoyl group is demonstrated as a novel protecting group for lactamic NH group. The structures of newly prepared compounds were established on the basis of spectral data (IR, H-1-NMR, and MS).