Hagerman stuctural hemistr The best characterized condensed tannins are linked via a carbon-carbon bond between C8 of the terminal unit and C4 of the extender.The four common modes of coupling are illustrated by the dimers isolated by Haslam,and originally named B-1,B-2,B-3 and B-4.The more complete names specify the position and stereochemistry of the interflavan bond completely.In addition to these dimers,related dimers linked by C6 of the terminal unit and C4 of the extender have been isolated. OH B-2 epicatechin-(4B->8)-catechin epicatechin-(40->8)-epicatechin B-3 catechin-(4a->8)-catechin chin-4a>8)-epicatechirHagerman condensed tannin structural chemistry 2/6 The best characterized condensed tannins are linked via a carbon-carbon bond between C8 of the terminal unit and C4 of the extender. The four common modes of coupling are illustrated by the dimers isolated by Haslam, and originally named B-1, B-2, B-3 and B-4. The more complete names specify the position and stereochemistry of the interflavan bond completely. In addition to these dimers, related dimers linked by C6 of the terminal unit and C4 of the extender have been isolated. HO O OH OH OH OH HO O OH OH OH OH HO O OH OH OH OH HO O OH OH OH OH B-3 catechin-(4α->8)-catechin B-4 catechin-(4α->8)-epicatechin HO O OH OH OH OH HO O OH OH OH OH HO O OH OH OH OH HO O OH OH OH OH B-1 epicatechin-(4β->8)-catechin B-2 epicatechin-(4β->8)-epicatechin