Syntheses of Glycyrrhetic Acid α-Diglycosides and Enol α-Glycosides

概要

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Glycyrrhetinate α-monoglycoside derivatives 8,10 and 12,all having a trichloroacetyl group at the C-2 position of the pyranose ring, were treated with NH_3-saturated ether at 0℃ to give the corresponding alcohols 13,15 and 17,accompanied by 2'-chloroderivatives, 14,16 and 18,respectively. Glycosylations of the alcohols 13,15 and 17 with methyl 2,3,4-tri-O-acetyl-α-D-glucuronatopyranosyl bromide 19 in the presence of AgOTf in dry CH_2Cl_2 gave the corresponding α-diglycosides 20,22 and 24 together with the enol α-glycosides 21,23 and 25,respectively. Glycosylations of the diglycoside derivatives 20,22 and 35 having no reactive OH group in the molecules with 19 for longer reaction times gave quantitatively the enol α-glycoside derivatives 21,23 and 36,respectively. Glycosylation of the monoglycoside derivative 37,which has a poorly reactive OH group at the C-4 position on the pyranose ring, with 19 gave an enol α-glycoside 38. The mechanism of the formation of enol α-glycosides was investigated. Removal of the protecting groups of 20,22 and 24 by successive treatment with 1.5N NaOMe in MeOH and 5% KOH in EtOH-H_2O (1 : 1) gave the free α-diglycosides 26-28,and removal of those of 31,21,23,25 and 36 by treatment with 5% KOH in EtOH-H_2O (1 : 1) under reflux gave the free enol α-glycosides 41-45,respectively.
社団法人日本薬学会の論文
1994-05-15