Hagerman condensed tannin structural chemistry prorobinetinidins comprise the major tannins found in quebracho and acacia tannin preparations. Acid butanol reaction yields the 5-deoxy anthocyanidins fisetinidn and robinetinidin. The acid butanol reaction can be carried out with a nucleophilic trapping agent to produce the terminal unit plus derivitized extender units.These can usually be separated and quantitated by HPLC to give composition and average molecular weight estimates for the parent tannin.Thiols such as toluene-a-thiol are often used in this reaction.but phloroglucinol is more convenient. The efficiency of the reaction with branched condensed tannins,especially the 5-deoxy-flavanol- based tannins has not been established OH HO 0 4B->8 cate OH 2eteialo9egoep Anothe r type of linkage that has been described but not studied extensively involves oxidative C O coupling between the flavonoid rings to yield A2 and related proanthocyanidins. OH epicatechin-()-epicatechin proanthocyanidin A-2 Hagerman condensed tannin structural chemistry 5/6 prorobinetinidins comprise the major tannins found in quebracho and acacia tannin preparations. Acid butanol reaction yields the 5-deoxy anthocyanidins fisetinidn and robinetinidin. The acid butanol reaction can be carried out with a nucleophilic trapping agent to produce the terminal unit plus derivitized extender units. These can usually be separated and quantitated by HPLC to give composition and average molecular weight estimates for the parent tannin. Thiols such as toluene-α-thiol are often used in this reaction, but phloroglucinol is more convenient. The efficiency of the reaction with branched condensed tannins, especially the 5-deoxy-flavanol￾based tannins, has not been established. Another type of linkage that has been described but not studied extensively involves oxidative C￾O coupling between the flavonoid rings to yield A2 and related proanthocyanidins. HO OH OH OH OH O O O OH OH HO OH epicatechin-(2β-->7,4β-->8)-epicatechin proanthocyanidin A-2 HO O OH OH OH OH O O O OH OH OH HO OH OH OH HO OH OH OH OH OH OH HO OH HO OH O OH OH HO OH OH OH OH HO 2 procyanidin epicatechin2 4β−−>8 catechin 2 derivitized extenders + catechin (end group) H+ H+ phloroglucinol (or other nucleophile)