Triterpene glycosides of alfalfa. III. Medicoside I
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On the basis of chemical transformations and with the aid of physicochemical results, the structure of glycoside I isolated from the roots of the plantMedicago sativa has been established as hederagin 3-O-[O-α-L-arabinopyranosyl-(1 → 2)-β-D-glucopyranosyl-(1 → 2)-α-L-arabinopyranoside] 28-O-β-D-glucopyranoside. Compound (I), C52H84O22, mp 210–212°C, [α] D 21 +38.4° (c 1.48; methanol). Acid hydrolysis of (I) led to hederogenin (II) — C30H48O4, mp 326–330°C, [α] D 23 +84.2° (c 0.19; pyridine. The Hakomorimethylation of glycoside (I) yielded the permethylate (IV) — C65H11O22 [α] D 23 +41.6° (c 1.79; methanol). The GLC analysis of the products of the methanolysis of compound (IV) showed the presence of 3,4,6-tri-O-methyl-D-glucopyranose, 2,3,4,6-tetra-O-methyl-D-glucopyranose, 3,4-di-O-methyl-L-O-arabinopyranose, and 2,3,4-tri-o-methyl-L-arabinopyranose. The alkaline hydrolysis of glycoside I gave compound (III) with mp 230–233°C, [α] D 21 +35.2° (c 0.21; methanol), which was identified as medicoside C. Details of the PMR spectrum are given for compound (IV) and of the IR spectrum for compound (I).
KeywordsGlycoside Anomeric Proton Triterpene Glycoside Hederagenin Tungstophosphoric Acid
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