Structure and Distribution of Oligomeric Proanthocyanidins

The past ten years have seen the description of new proanthocyanidins in every class from the proguibourtacacidins through to the prodelphinidins. Much of the 

The proguibourtinidins obtained from Guibourtia coleosperma that carry a 3,4,3, 5-tetrahydroxystilbene terminating unit are among the most interesting proanthocyanidins that have been isolated recently. As in most other ly i-cis proanthocyanidins the compound 50 contains only [4-yff] or A-trans substitution. The 2, i-trans dimer has a [4-a] bond and, interestingly, the trimer 51 has both a 2,3-cis and a 2,3-trans proanthocyanidin unit (345). Another trimer with mixed 2,3-stereochemistry in the proguibourtinidin units was isolated, but its structure was not defined. 

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