Tannins and Related Compounds. VIII. A New Type of Proanthocyanidin, Cinchonains IIa and IIb from Cinchona succirubra. (2)

Abstract

Together with known proanthocyanidins B-2 (7), B-5 (8), A-2 (9) and C-1 (10), consisting exclusively of (-)-epicatechin (C₂, C₃ : cis) units, cinchonains IIa and IIb were isolated from red cinchona, the bark of Cinchona succirubra (Rubiaceae). They have been established on the basis of degradative studies, and ¹H- and ¹³C-NMR evidence to be novel proanthocyanidin dimers containing a phenylpropanoid substituent.