Triterpene glycosides of astragalus and their genins. Lxi. occurrence of cycloartane 6-o-monodesmosides

摘要

Cyclosiversigenin 6-O-#alpha#-L-rhamnopyranoside and 6-O-#beta#-D-glucopyranoside were idolated from Astragalus coluteocarpus Boiss. (Leguminosae)and Astragalus dissectus B.Fedtsch. et N.Ivanova, respectively. Cyclosiversigenin 5-O-#alpha#-L-rhamnopyranoside was shown to be an artifact for Astragalus coluteocarpus. Thus, the cyclosiversigenin 6-O-#beta#-D-glucopyranoside that was isolated from certain Astragalus species is hypothesized also to be an artifact. Glycosylation of the 6#alpha#-hydroxyl group of cycloartanes by D-glucose and D-xylose, in contrast with other substituents, does not change the low-field position of the PMR signal of the 4#alpha#-CH_3 group (1.65 <=#delta# <= 2.01 ppm) that is caused by the influence of deuteropyridine directly on the 6#alpha#-hydroxyl. Obviously one of the hydroxyls of the #beta#-D-glucopyranoside or #beta#-D-xylopyranoside residues has the same effect in this instance.