Tannins and related compounds. VII. Phenylpropanoid-substituted epicatechnins, cinchonains from Cinchona succirubra. (1).

As a result of an investigation of the relatively lower-molecular-weight phenolics in the bark of Cinchona succirubra (Rubiaceae), cinchonains Ia (1), Ib (2), Ic (3) and Id (4), a new class of flavan-3-ols substituted at the A-ring with a C6-C3 unit, have been isolated, together with caffeic acid (5) and (-)-epicatechin (6). The structures of these compounds have been established on the basis of chemical and spectroscopic evidence. A direct coupling of caffeic acid and (-)-epicatechin leading to the formation of cinchonains has also been achieved.