Journal of the Chemical Society. Perkin transactions I p. 581 - 591 (1996)
Update date:2022-08-04
Topics:
Wang, Lai-Xi
Lee, Yuan C.
A stereoselective synthesis of N-acetyl-thiochito-di-, -tri- and -tetra-saccharides is described. Coupling of methyl 2-acetamido-3,6-di-O-benzoyl-2-deoxy-4-O-triflyl-β- 4 or -α-D-galactopyranoside 19 with 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-1-thio-β-D-glucopyranose 5 in the presence of cysteamine in DMF gave, after de-O-acylation, methyl N,N′-diacetyl-β- 9 and -α-thiochitobioside 21, respectively. Different behaviours of peracetylated methyl β- 10 and α-thiochitobioside 22 towards acetolysis with Ac2O-AcOH-H2SO4 solution were observed, with the β-isomer giving acyclic sugar species together with the desired thiochitobiose peracetate 11, while the α-isomer gave exclusively the thiochitobiose peracetate 11. This remarkable difference between α- and β-glycosides was further demonstrated by comparative acetolysis of methyl 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-α- 23 and -β-D-glucopyranoside 24. Methyl N,N′,N″-triacetylthiochitotriosides 29 and 30 were synthesized through conversion of N,N′-diacetylthiochitobiose peracetate 11 into N,N′-diacetyl-1,4-dithiochitobiose derivative 28, followed by its coupling with triflates 4 and 19 in the presence of cysteamine. Similarly, extension of the sugar chain to a higher homologue was achieved by converting methyl N,N′,N″-triacetylthiochitotrioside 30 into the N,N′,N″-triacetyl-1,4,4′-trithiochitotriose derivative 33, the coupling of which with triflate 19 in the presence of cysteamine provided the methyl N,N′,N″,N?-tetraacetylthiochitotetraoside 34 after de-O-acylation. Copyright 1996 by the Royal Society of Chemistry.
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Doi:10.1016/0957-4166(96)00055-9
(1996)Doi:10.1080/00945719608004761
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(1996)
