Epicatechin Epifisetinidol

Epifisetinidol-(4p —> 8)-catechin Epifisetinidol-(4p —> 8)-epicatechin Pithecellobium dulce 114... 

Although a number of flavan-3-ols of the IS configuration are known, their distribution is quite restricted in comparison with the above compounds. Both eAZ/-epiafzelechin and eA epicatechin are found in several species of the Palmae (73). Afzelia xylocarpa and Colophospermum mopane contain eA2/-fisetinidol, and e epifisetinidol is also present in the latter species (66, 82, 323). The flavan-3-ols readily undergo epimerization through inversion of configuration at C-2, making precautions necessary in their isolation. The above compounds clearly are not artifacts, however. 

With the knowledge that flavan-3,4-diols are freely associated with flavan-3-ols [e. g. (H-)-catechin, (—)-epicatechin, ( —)-fisetinidol, ( + )-epifisetinidol] in tannin mixtures comprised of these molecular entities, experimental conditions were sought which would permit formation of C-4 —C-6 or 8 interflavanoid links. The conditions selected had to be sufficiently mild to avoid self-condensation of the flavan-3,4-diol, to avoid anthocyanidin formation as a side-reaction, to permit stereochemical conclusions (i. e. the reaction should be under kinetic rather than under thermodynamic control), and to allow assessments regarding the re-gioselectivity of the condensation. 

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