Abstract

Catechin was used as a model for condensed vegetable tannins, to elucidate the reaction between the fiavonoid ring system and oxazolidines in the combination tannage. Using ‘H-NMR 13C-NMR and paper chromatography, it is shown that the crosslinking reaction occurs predominantly at the C-6 and C-8 of the phloroglucinol A ring of catechin. The crosslinker reacts at the C-5 of oxazolidine, by ring opening and reacting via the N-methylol intermediate.