Synthesis of modified proanthocyanidins: easy and general introduction of a hydroxy group at C-6 of catechin; efficient synthesis of elephantorrhizol

A general procedure for the oxidation of catechin derivatives is described, leading to the introduction of a new hydroxy group at C-6. This procedure has been applied for the synthesis of elephantorrhizol, a natural flavan-3-ol exhibiting a fully substituted cycle A.