Synthesis of 6-thia analogs of the natural neurosteroid allopregnanolone

Abstract

A procedure is described for the preparation of 6-thiapregnanes in five steps from pregnenolone via a 5-oxo-7-iodo-secopregnane intermediate. The 6-thiasteroid obtained was converted into 6-thia-allopregnanolone and its sulfoxide and sulfone derivatives. The trans stereochemistry at the A/B ring junction was accomplished by stereoselective reduction of an intermediate hemithioketal with triethylsilane/BF3·Et2O. The compounds synthesized are analogs of natural neurosteroids, and exhibited GABAA receptor activity comparable to allopregnanolone.