MECHANISM OF FORMATION OF ANTHOCYANIDINS FROM FLAVAN-3,4-DIOLS

Abstract

Conversion by hydrochloric acid in 2-propanol of 5,7:3′,4′-tetramethoxyflavan-3,4-diol (I; R = OMe) into cyanidin chloride 5,7:3′,4′-tetramethyl ether is examined. The diol is wholly changed into the anthocyanidin. The over-all reaction mechanism must therefore be oxidative, since the alternative of disproportionation is excluded. Fading of this anthocyanidin in solution is studied. Attempts to synthesize flavan-3-one derivatives are briefly described.