Tannins and related compounds. XXIX. Seven new methyl derivatives of flavan-3-ols and a 1,3-diarylpropan-2-ol from Cinnamomum cassia, C. obtusifolium and Lindera umbellata var. membranacea.

Abstract

Seven new methyl derivatives of flavan-3-ols (compounds 1-7) and one 1, 3-diarylpropan-2-ol (compound 8) were isolated from three Lauraceous plants (1, and 3-7 from Cinnamomum cassia, 1, 3 and 4 from Cinnamomum obtusifolium, and 1-4 and 8 from Lindera umbellata var. membranacea). Their structures were characterized mainly by proton nuclear magnetic resonance (1H-NMR) examination combined with nuclear Overhauser effect (NOE) experiments as the 3'-O-methylate (1), 3', 4'-di-O-methylate (2), 5, 3'-di-O-methylate (3) and 5, 7, 3'-tri-O-methylate (4) of (-)-epicatechin, the 4'-O-methylate (5), 7, 4'-di-O-methylate (6) and 5, 7, 4'-tri-O-methylate (7) of (+)-catechin, and 1-(4', 6'-dihydroxy-2'-methoxyphenyl)-3-(4'-hydroxy-3"-methoxyphenyl)-propan-2-ol (8).