Linkage isomerism in trimeric and polymeric 2,3-cis-procyanindins

Abstract

Procyanindins polymers consist of chains of 5,7,3',4'-tetrahydroxyflavan-3-ol units linked by C(4)-C(6) or C(4)-C(8) bonds.¹ Whereas the procyanidin-B group of dimers are known to exist as pairs of isomers with common flavan-3-ol units, but different interflavanoid linkages,^2,3 the extent of such isomerism in higher molecular weight procyanidins is unknown. A number of trimeric procyanidins have been isolated,^4-7 but no unequivocal proof of their structure has been offered. Large numbers of isomers are possible since the trimeric procyanidins consist of two procyanidin (PC) units each containing three asymmetric centres, a 6,7,3',4'-tetrahydroxyflavan-3-ol chain-terminating unit containing two chiral centres, and C(4)-C(6) or C(4)-C(8) interflavanoid linkages.

Citation

Hemingway, Richard W.; Foo, Lai Yeap; Porter, Lawrence J. 1982. Linkage isomerism in trimeric and polymeric 2,3-cis-procyanindins. Journal of the Chemical Society Perkin I:1209-1216