Tannins of Cornaceous Plants. I. Cornusiins A, B and C, Dimeric Monomeric and Trimeric Hydrolyzable Tannins from Cornus officinalis, and Orientation of Valoneoyl Group in Related Tannins

Cornusiin A (1), cornusiin B (2) and cornusiin C (3), new dimeric, monomeric and trimeric hydrolyzable tannins, were isolated from the fruits of Cornus officinalis (Cornaceae). Their structures, including the orientation of the valoneoyl group in 1 and 3, were established on the basis of chemical and spectroscopic data. 2,3-Di-O-galloyl-D-glucose (7), l,2,3-tri-0-galloyl-/?-D-glucose, l,2,6-tri-0-galloyl-/f-D-glucose, l,2,3,6-tetra-0-gaIloyl-/?-D-glucose, gemin D (5), isoterchebin, tellimagrandin I (6) and tellimagrandin II were also isolated from the fruits. The orientation of the valoneoyl group in camptothin A (14) and that in camptothin B (15), which had been isolated from Camptotheca acuminata (Nyssaceae), were also determined based on that in 1.