Elimination reaction of angular hydroxymethyl groups of 20(29)-lupene derivatives

Abstract

Solvolysis of 28-p-toluenesulfonyloxy-20(29)-lupene derivatives IV-VII proceeds with isomerization of the isopropenyl side chain to the isopropylidene chain and expansion of the ring E to a six-membered ring, containing trisubstituted double bond; for „anhydrobetulin" and its derivatives formulae VIII-XI with homoconjugated double bonds are suggested. Formation of a conjugated diene system is hindered by steric interactions of the isopropylidene chain with the ring C (with C(12)). Only the trisubstituted double bond in the dienes VIII and X undergoes catalytic reduction, the hydrogen approaching from the α-side (XII-XVI) as demonstrated by the Cotton effect of trinorketone XXI and its 20,20-dibromo derivative XXIII.