Short and stereoselective construction of a key intermediate for synthesis of unsymmetrical pentacyclic triterpenes

Abstract

A key intermediate, 10-ethoxy-3-methoxy-6bβ, 12bα, 14aβ-trimethyl-5,6,6aα, 6b,7,8,12b,13,14,14a-decahydropicene (1), for synthesis of pentacyclic triterpenoids has been stereoselectively synthesised; the key stage is an intramolecular cycloaddition of the o-quinodimethane (19) to give the corresponding cyclised compound (4).