Studies on Digitalis Glycosides. XXVII. Alkoxy-and Cyclocarbonates of Gitoxin

概要

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Treatment of gitoxin (I) with alkyl chloroformate in pyridine gave rise to alkoxycar-bonylation of hydroxyl groups in the order of 4'''-, 16- and 3'''-positions analogously to acetylation to afford gitoxin 4'''-mono-, 4''', 16-di-and 3''', 4''', 16-trialkoxycarbonates (II, III, IV), but the further esterification encountered with more difficulties than the acetylation. Gitoxin 3''', 4'''-cyclocarbonate (V) was also prepared and the interconversion between 3'''-mono-and 4'''-monomethoxycarbonates (VIIa, IIa) and V was investigated. Alkyl pyrocarbonates showed a less selectivity in alkoxycarbonylation of I than alkyl chloroformates, resulting in the formation of V, 16-alkoxy-and 3''', 4'''-cyclocarbonyl-16-alkoxycarbonates (IX, VIII) besides II, III and IV. IX was also formed by partial hydrolysis of III and VIII with dilute alkali.
社団法人日本薬学会の論文
1969-04-25