Synthetic studies of proanthocyanidins.Part 4.~1 The synthesis of procyanidin B1 and B4:Tmsotf-catalyzed cyclization of catechin and epicatechin condensation

摘要

Highly stereoselective synthesis of 3,4-trans series of (+)-catechin and (-O)-epicatechin dimers under intramolecular condensation is described.Intramolecular condensation achieved an equimolar amount of coupling with 3,4-trans stereoselectivity and we succeeded in the synthesis of two 3,4-trans natural procyanidins,procyanidin-B1 and B4.