PHOTOINDUCED MOLECULAR-TRANSFORMATIONS .131. SYNTHESIS OF 18-NORSTEROIDS, DEOXOFUKUJUSONORONE AND THE RELATED STEROIDS, BASED ON A SELECTIVE BETA-SCISSION OF ALKOXYL RADICALS AS THE KEY STEP

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