Oxidation of 3-oxo-4-oxa-5beta-cholestane

TLDR: In this paper, the authors presented a novel method of pre-preparing steroids in the presence of the 3-OXO-4-ENE groupings, from TETRACYCLIC TRITERPENes SUCH as LANOSTEROL.

Abstract: THERE IS PROVIDED A NOVEL METHOD OF PREPARING STEROIDS HAVING THE CYCLOPENTANOPHENANTHRENE NUCLEUS, IN PARTICULAR THOSE POSSESSING THE VALUABLE 3-OXO-4-ENE GROUPINGS, FROM TETRACYCLIC TRITERPENES SUCH AS LANOSTEROL THE METHOD COMPRISES CONVERTING LANOSTEROL TO THE CORRESPONDING 3B-HYDROXY-5A-LANOSTANE WHICH IS THEN SUBJECTED TO A-RING CONTRACTION TO GIVE THE KNOWN 3-OXO-ANOR-14A-METHYL CHOLESTANE THE FIVE MEMBERED "A" RING IS CONVERTED TO THE CORRESPONDING 3-OXO-4-OXA COMPOUND THIS LACTONE IS OXIDIZED TO THE CORRESPONDING 3,5-SECO-5OXO-3-OIC ACID, DEHYDRATION LEADS TO RING CLOSURE AND FORMATION OF THE $5 LACTONE THIS $5 LACTONE IS CLEAVED BY, FOR EXAMPLE, THE ACTION OF A GRIGNARD AGENT TO YIELD THE CORRESPONDING TRICYCLIC 3,5-DIONE WHICH IS RING CLOSED BY THE ACTION OF A STRONG BASE TO GIVE THE CORRESPONDING VALUABLE 3-OXO-4-ENE STEROID THE METHOD HAS GREAT AND SURPRISING FLEXIBILITY IN BEING SUBSTANTIALLY UNAFFECTED BY SUBSTITUTION PATTERNS IN THE B, C OR D RINGS OF THE NUCLEUS THE METHOD THUS PRESENTS LANOSTEROL AS A CHEAP AND READILY AVAILABLE RAW MATERIAL FOR MOST KNOWN STEROIDS AND IS THUS A DESIRABLE ALTERNATIVE TO THE PRESENTLY USED DIOSGENIN FOR THIS PURPOSE