Preparation of antiandrogenic 17-hydroxy-3,6-cyclo-4-nor-3,5-seco-6β-androstan-3-one by deoxygenation of the corresponding 5-hydroxy derivatives

Abstract

This paper reports on three alternative procedures for the preparation of antiandrogenic 17β-hydroxy-3,6-cyclo-4-nor-3,5-seco-6β-androstan-3-one 15. The key step represents the removal of the oxygen functional group from position 5 which was effected by radical deoxygenation of thioesters of type 13. The variant of choice was the deoxygenation of the 5-thioimidazolide 29 prepared from diketone 5. The 3-keto group was selectively protected during hydride reduction by conversion into the corresponding silyl enol ether.