APPLICATION OF A RADICAL METHODOLOGY TOWARD THE SYNTHESIS OF D,L-5-ALPHA-PREGNANES AND RELATED STEROIDS - A STEREOSELECTIVE RADICAL CASCADEAPPROACH

A stereoselective radical cascade cyclization to 5 alpha-pregnanes is presented. Oxidative free radical cyclization of an appropriately subs tituted chloro cyano ester polyene was used to introduce the all trans stereochemistry in the steroid nucleus. The cyano group was utilized to introduce a C-8 beta angular hydrogen, while the chloro ester moiet y served as an entry to the geminal hydrogens at C-4.