Tannins and Related Compounds. LXXXV. : Structures of Novel C-Glycosidic Ellagitannins, Grandinin and Pterocarinins A and B

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The structures of three hydrolyzable tannins, i.e., grandinin (3) (isolated from various species of Myrtaceae, Fagaceae and Lythraceae), pterocarinin A (4) (from Pterocarya steroptera C.DC. and Eucalyptus viminalis LABILL.) and pterocarinin B (6) (from P. stenoptera), have been established on the basis of chemical and spectroscopic evidence as novel C-glycosidic ellagitannins in which a C₅-polyalcohol unit with lyxose-type configuration is linked through a carbon-carbon bond to the C-1 position of the C-glycosyl moiety. Successful biomimetic synthesis of 3 and 4 suggests that the C₅-polyalcohol unit is biosynthetically derived from L-ascorbic acid.