名称:
Selective Reactions of the Free Hydroxyl Groups of 2,3,4,3′,4′-Penta-O-Benzylsucrose
摘要:
Selective transformations of the free hydroxyl groups in 2,3,4,3',4'-penta-O-benzylsucrose (1) were studied. Oxidation of 1 with the Swern reagent followed by reaction with Ph(3)P=CH-COOMe gave 2,3,4,3',4'-penta-O-benzyl-1',6,6'-tris-(E)(C-carbomethoxymethylene)sucrose (2) in ca.40% as the single product. Reaction of 1 with p-nitrobenzoic acid under Mitsunobu conditions gave 6,6'-di-O-p-nitrobenzoyl-2,3,4,3',4'-penta-O-benzylsucrose (3) which was easily converted into 2,3,4,3',4'-penta-O-benzyl-1'-methoxymethylsucrose (5). Reaction of 1 with one equivalent of pivaloyl chloride gave monoprotected 2,3,4,3',4'-penta-O-benzyl-6'-O-pivaloylsucrose (6) [30% with triethylamine or 45% yield in the presence of (Bu(3)Sn)(2)O] together with a small amount of diprotected 2,3,4,3',4'-penta-O-benzyl-6,6'-di-O-pivaloylsucrose (7).