New Synthesis of Finasteride

The document described a new synthesis method for Finasteride, starting from pregnenolone. The process involved converting pregnenolone to 3 carbonyl 4 androstene 17β carboxylic acid, which was then reacted with oxalyl chloride and t-butyl amine to form 17β carboxamide. This compound underwent ring cleavage and closure with ammonia to form a 4 aza steroid, which was hydrogenated to produce a 5α 4 aza steroid. Finally, dehydrogenation at the 1,2 position yielded Finasteride. This method avoided the use of the expensive reagent 2,2′ dipyridyl disulfide and achieved an overall yield of 16%.