Effects of O-methylation and O-glucosylation on Carbon-13 nuclear magnetic resonance chemical shifts of matairesinol, (+)-pinoresinol and (+)-epipinoresinol.

Abstract

The effects of O-methylation and O-glucosylation on the carbon-13 nuclear magnetic resonance chemical shifts of matairesinol (1), (+)-pinoresinol (6) and (+)-epipinoresinol (11) are discussed. The chemical shifts of carbons on the 2, 3-dibenzylated butyrolactone and 2, 6-diarylated 3, 7-dioxabicyclo [3. 3. 0] octane rings are not affected by methylation and glucosylation of hydroxy groups on the aromatic rings. As regards the chemical shifts of aromatic carbons caused by O-methylation, all the 1'(1), 3'(3), and 4'(4) carbons of the guaiacyl unit are characteristically shifted downfield by 1.6±0.1, 1.3±0.1, and 2.4±0.1 ppm, respectively, while the 5'(5) carbons are shifted upfield by 3.5±0.1 ppm. In the case of the chemical shifts of aromatic carbons caused by O-glucosylation, all the 1'(1) and 3'(3) carbons of the guaiacyl unit are characteristically shifted downfield by 3.0±0.1 and 1.3±0.1 ppm, respectively.