Oligomeric Hydrolyzable Tannins From Liquidambar Formosana and Spectral Analysis of the Orientation of Valoneoyl Groups in Their Molecules
The leaves of Liquidambar formosana (Hamamelidaceae), used as herbal medicines, contain a complex array of hydrolyzable tannins including dimers and trimers. The structures of the dimer isorugosin E (11) and the trimer isorugosin G (12) were defined for the first time. In addition, application of NMR and CD spectroscopic data permitted assignment of the orientation of the valoneoyl groups in the isomeric pairs of dimers (11) and rugosin E (14) as well as the trimers (12) and rugosin G (20). The rules defined for these compounds are applicable to assignment of the structure of other isomeric pairs.
KeywordsUpfield Shift Hydrolyzable Tannin Anomeric Carbon Isomeric Pair Anomeric Center
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