Chemistry of 3-oxoflavans: Oxidation of (+)-catechin 5,7,3',4'-Tetramethyl ether to (+)-5,7,3',4'-Tetramethoxy-3-oxoflavan

Abstract

Crystalline (+)-5,7,3?,4?-tetramethoxy-3-oxoflavan has been prepared by oxidation of (+)-catechin 5,7,3?,4?-tetramethyl ether, and characterized by ketonic derivatives. The formation of acetals and of 3-alkoxyflav-3-enes by interaction of the 3-oxoflavan with acidified alcohols has been investigated, and the N.M.R. spectra of the products recorded. The 2R-configuration of the (+)-3-oxoflavan was confirmed by reducing it to a mixture of (+)-catechin and (-)-epicatechin tetramethyl ethers. The 3-oxoflavan readily gives the tetramethoxyflavylium cation when heated with acids in air.