Quinoline alkaloids. Part XV. Reactions of a quinoline isoprenyl epoxide with hydride reagents. Asymmetric synthesis and stereochemistry of lunacridine and related Lunasia alkaloids

Abstract

Reaction of (–)-3-(2,3-epoxy-3-methylbutyl)-2,4,8-trimethoxyquinoline, of known configuration, with diborane–lithium borohydride or with lithium aluminium hydride–aluminium chloride gave a secondary alcohol which was converted into (–)-lunacridine. The stereochemistry ofLunasiaalkaloids is discussed. Reductive displacement of 4-methoxy-groups in 2,4,8-trimethoxyquinoline derivatives occurs with lithium aluminium hydride. Rearrangement products obtained from the quinoline epoxide with mixed hydrides and with acid are described.