Tannins of Hamamelidaceous Plants. III. Isorugosins A, B and D, New Ellagitannins from Liquidambar formosana

Abstract

A new dimeric hydrolyzable tannin named isorugosin D (11), and two new monomeric tannins of related structures, isorugosin A (10) and isorugosin B (1), were isolated from the leaf of Liquidambar formosana HANCE (Hamamelidaceae). The orientation of the valoneoyl group at 0-4 and 0-6 of the glucose core in isorugosins A, B and D was found to be different from that of rugosin A (7), rugosin B (6) and rugosin D (18), and the orientations of this group in the tannins of both type were confirmed on the basis of the two-dimensional nuclear magnetic resonance spectrum (long-range ¹H-¹³C correlation spectrum) of rugosin A (7).