PHOTOINDUCED MOLECULAR-TRANSFORMATIONS .112. TRANSFORMATION OF STEROIDS INTO RING-A-AROMATIZED STEROIDS AND 19-NORSTEROIDS INVOLVING A REGIOSELECTIVE BETA-SCISSION OF ALKOXYL RADICALS - SYNTHESIS OF 2 MARINE NATURAL-PRODUCTS, 19-NOR-5-ALPHA-CHOLESTAN-3-BETA-OL AND 19-NORCHOLEST-4-EN-3-ONE, AND NEW SYNTHESIS OF ESTRONE AND 19-NORTESTOSTERONE

A new transformation of steroids into 19-norsteroids and ring-A-aromatized steroids is described. The transformation method involves the removal of the 10β-methyl group by a regioselective β-scission of alkoxyl radicals. Cholesterol was transformed into two marine natural products, 19-nor-5α-cholestan-3β-ol and 19-norcholest-4-en-3-one, and into 19-norcholesta-1,3,5(10)-trien-3-ol. Transformations of 3β-hydroxyandrost- 5-en-17-one into 19-nortestosterone, estrone, and the related estranes are also described.