Dimeric and trimeric hydrolyzable tannins from Quercus coccifera and Quercus suber

Three new hydrolyzable tannins, cocciferins. D-1 (1), D-2 (2), and T-1 (4), were isolated from the leaves of Quercus coccifera. Cocciferin D-2 (2) and two additional new tannins, cocciferins D-3 (3) and T-2 (5), were also obtained from the leaves of Quercus suber. Their oligomeric structures were elucidated on the basis of spectroscopic methods and chemical evidence. Compounds 2, 3, and 5 were rare oligomers possessing glucose cores with both open-chain and pyranose forms.