Synthesis of methyl 4-thio-β-cellobioside. A reinvestigation
作者:Vincent Moreau、Jens Chr. Norrild、Hugues Driguez
DOI:10.1016/s0008-6215(97)00046-3
日期:1997.5
Abstract The best yield for the synthesis of the title compound was obtained by nucleophilic displacement of the 4- O -triflyl group in methyl tri -O- benzyl -4-O- triflyl -β- d - galactopyranoside by 2,3,4,6- tetra -O- acetyl -1-S- acetyl-1-thio -β- d - glucopyranose in HMPA in the presence of diethylamine. Under these conditions, the formation of unsaturated side products was decreased.
The preparation of the previously undescribed class of 4-deoxy- and 2,4-dideoxy-2-acetamido-beta-D-threo-hex-3-enopyranosides was accomplished with a very high yield and a complete regioselectivity by means of a simultaneous activation-elimination process of the OH-4 group of beta-D-talopyranosides (5a,b) and 2-acetamido-2-deoxy-beta-D-talopyranosides (5c,d) with NaH/'N,N'-sulfuryldiimidazole. The same reaction of analogous beta-D-galactopyranosides (5e,f) is not regioselective, leading to mixtures of 3- and 4-hexeno derivatives. This difference is evidently determined by the orientation of the C-2 substituent, which, in the talo series, is anti diaxially disposed to the H-3 eliminating group. (C) 2002 Elsevier Science Ltd. All rights reserved.