6S, 8R-Stereochemistry of the C_<27>- and C_<29>-Alkane-6,8-diols Isolated from Three Compositae Flowers

概要

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The Δδ(δ_S-δ_R) values for the C-1 methyl ^1H signals in the ^1H-NMR spectroscopy of the bis-MTPA esters of four synthetic stereoisomers of alkane-6,8-diols, viz., bis-MTPA esters of (6S, 8R)-C_<27>- (1a) and C_<29>- (3a) (Δδ=-0.05 ppm), (6R, 8S)-C_<27>- (2a) and C_<29>- (4a) (Δδ=+0.05 ppm), (6S, 8S)-C_<27>- (5a) (Δδ=-0.01 ppm), and (6R, 8R)-C_<27>- (6a) (Δδ=+0.01 ppm) alkane-6,8-diols, made it possible to differentiate unequivocally among the four stereoisomers. This allowed the determination of the (6S, 8R)-stereochemistry (Δδ=-0.05 ppm for the bis-MTPA esters) for the natural C_<27>- and C_<29>-alkane-6,8-diols isolated from the flowers of three Compositae plants, Carthamus tinctorius, Cynara cardanclus, and Taraxacum platycarpum.
2000-08-01