Trityl Derivatives of Cellobiose. V. Selective Acetylation of 6- and 6'-Mono-O-tritylcellobiose and Their Methyl β-Glycosides

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The selective acetylation of 6'-O-tritylcellobiose (1), 6-O-tritylcellobiose (3), and their methyl β-glycosides (2 and 4) with 6 molar equivalents of acetyl chloride in pyridinetoluene at 1-4℃ has been studied. Acetylation of 1 gave the 1,2,6,2', 3', 4'-hexaacetate (1A) and 1,2,6,2', 3'-pentaacetate (1B), and that of 3 gave the peracetate, 1,2,2', 3', 4', 6'-hexaacetate (3A), and 1,2,3,3', 4', 6'-hexaacetate (3B). On the basis of the yields of partially acetylated products from 2,i.e., 2,6,2', 3', 4'-pentaacetate (2A, 15.5%), 2,6,2', 3'-tetraacetate (2B, 16.2%), 2,6,3', 4'-tetraacetate (2C, 10.8%), 6,2', 3', 4'-tetraacetate (2D, ca. 10.6%), 6,2', 3'-triacetate (2E, 7.9%), 2,6,3'-triacetate (2F, ca. 10.5%), and 3,6,2', 3'-tetraacetate (2F', ca. 6.9%), it was deduced that the order of reactivities of the secondary hydroxyl groups in 2 is 3'>2'≃2>4'≫3. The partially acetylated products from 4 were separated by column chromatography and semipreparative HPLC to afford the peracetate (17.7%), 2,2', 3', 4', 6'-pentaacetate (4A, 11.1%), 2,3,3', 4', 6'-pentaacetate (4B, 26.0%), and 2,3,2', 3', 6'-pentaacetate (4C, 6.5%). It seems likely that the order of reactivities of the secondary hydroxyl groups in 4 toward acetyl chloride is 2,3'>4'>3>2'. These results suggested that TrO-6' interacts sterically with HO-3 and HO-4', while TrO-6 affects only HO-2'.
公益社団法人日本薬学会の論文
1981-10-25