Hydroxylation of Ring A of Flavan-3-ols: Influence of the Ring A Substitution Pattern on the Oxidative Rearrangement of 6-Hydroxyflavan-3-ols

Abstract

A general procedure for the oxidation of catechin derivatives is described, leading to the introduction of a new hydroxyl group at C-6. This procedure has been used for the synthesis of a number of 6-hydroxy flavan-3-ols, including elephantorrhizol, a natural flavan-3-ol exhibiting a fully substituted A ring. The substitution at C-8, albeit of poor influence on the course of this oxidation reaction, has been demonstrated to be preponderant for the further spontaneous oxidation and rearrangement of 6-hydroxy-flavan-3-ols into p-benzoquinones. The whole procedure allows the preparation of 6-alkyl substituted benzoquinones derived from catechin.

Key words

phenols - quinones - oxidations - rearrangements - dioxiranes

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