(+)-Catechin—acetaldehyde condensation products in relation to wine-ageing

Abstract Dimers resulting from acetaldehyde-flavanol condensation were studied in an acidic hydroalcoholic medium (12% ethanol pH 3.2) in order to simulate the conditions of wine tannin-transformation during the wine-ageing process. One of the dimers was isolated after hemisynthesis and studied by mass spectrometry, NMR and molecular mechanics. Mass spectrometric analysis was in accordance with a dimeric structure with a CH-CH 3 linkage. NMR showed the presence of a 6–8 (ethane-1,1-diyl)di(+)-catechin. The carbon atoms, C-6 and C-8, involved in the linkage, have, an asymmetric conformation, with the two catechols in an equatorial position.