Tannins and Related Compounds. LV. Isolation and Characterization of Acutissimins A and B, Novel Tannins from Quercus and Castanea Species

Abstract

Two novel and closely related tannins, designated as acutissimins A (1) and B (2), have been isolated from various Fagaceous plants : Quercus acutissima, Q. miyagii, Q. stenophylla, Q. mongolica var. grosseserrata and Castanea crenata. Degradative and synthetic studies combined with ¹H- and ¹³C-NMR spectrometry and various mass spectral measurements have permitted the assignments. of the structures, in which (+) -catechin (4) and the C-glycosylated ellagitannin, castalagin (3), are connected through a carbon-carbon linkage.