A new approach to the chemical synthesis of the trisaccharide, and the terminal di- and mono-saccharide units of the major, serologically active glycolipid from Mycobacterium leprae.
The key intermediates for the synthesis of p-trifluoroacetamidophenyl O-(3,6-di-O-methyl-beta-D-glucopyranosyl)-(1-->4)-O-(2,3-di-O-methyl-alp ha-L- rhamnopyranosyl)-(1-->2)-3-O-methyl-alpha-L-rhamnopyranoside (15), as well as p-trifluoroacetamidophenyl O-(3,6-di-O-methyl-beta-D- glucopyranosyl)-(1-->4)-2,3-di-O-methyl-alpha-L-rhamnopyranoside (29), were the methyl and ethyl O-(2-O-benzyl-4,6-O-benzylidene-3-O-methyl-beta- D-glucopyranosyl)-(1-->4)-2,3-O-diphenylmethylene-1-thio-alpha-L- rhamnopyranosides (10 and 24). Dichloroalane treatment of 10 and 24 removed the diphenylmethylene group, liberating HO-2 and HO-3 of the rhamnopyranoside residue, and opened the benzylidene acetal regioselectively to give the 4-O-benzyl-glucopyranosyl disaccharides. Methylation of the free OH groups resulted in the tetra-O-methyl 1-thio disaccharides (12 and 26), useful as glycosyl donors. Introduction of these temporary blocking groups allowed a drastic reduction in the number of synthetic steps to the target compounds.
Borbás
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Department of Biochemistry, L. Kossuth University, Debrecen, Hungary.
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D000942:Antigens, Bacterial / Q000737:chemistry*; D002240:Carbohydrate Sequence; D004187:Disaccharides / Q000737:chemistry; D006017:Glycolipids / Q000737:chemistry*; D008757:Methylglucosides / Q000737:chemistry; D008969:Molecular Sequence Data; D009005:Monosaccharides / Q000737:chemistry; D009166:Mycobacterium leprae / Q000737:chemistry*; D012210:Rhamnose / Q000031:analogs & derivatives; D014312:Trisaccharides / Q000138:chemical synthesis*
D000942:Antigens, Bacterial; D004187:Disaccharides; D006017:Glycolipids; D008757:Methylglucosides; D009005:Monosaccharides; D014312:Trisaccharides; D012210:Rhamnose