Condensed tannins: condensation mode and sequence during formation of synthetic and natural triflavonoids

Abstract

The first synthesis of 4,8:4,6-linked all-trans- and 2,3-trans-3,4-trans: 2′,3′-trans: 2″,3″-trans-3″,4″-cis-bi[(–)-fisetinidol]-(+)-catechins and recognition of their distribution in nature gives an insight into the mode and sequence of condensations leading to such key triflavonoid intermediates during tannin formation; the synthesis taken in conjuction with c.d. spectra established their absolute configurations.