Photoinduced molecular transformations. Part 131. Synthesis of 18-norsteroids, deoxofukujusonorone and the related steroids, based on a selective β-scission of alkoxyl radicals as the key step

Abstract

A new transformation of steroids into 18-norsteroids under mild conditions is described. The key step was a regioselective β-scission of the alkoxyl radicals generated by photolysis of the hypoiodite of 18-hydroxy-18,20α-epoxy steroids, prepared by photolysis of steroidal 20α-ol nitrites followed by deoximation of the resulting 18-hydroxyimino-20α-hydroxy steroid with sodium nitrite and acetic acid. 3β-Hydroxypregn-5-en-20-one (pregnenolone) was thus transformed into 3β-hydroxy-18-norpregna-5,13-dien-20-one (12-deoxofukujusonorone) in 10 steps.