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Selective defucosylation by mercaptolysis. A potential step in analyzing branched oligosaccharides
J Lehmann1, S Petry, M Scheuring
1Institut für Organische Chemie und Biochemie der Universität Freiburg, Germany.
Abstract:
A method of stepwise chemical degradation was elaborated on a microgram quantity of 3-O-alpha-L-fucosyllactose. The key step, TiCl4-catalysed dithioacetal formation from the permethylated N-4-nitrophenyl triosylamine (4) was accompanied by quantitative defucosylation. [14C]Acetylation of the dried mercaptalation mixture gave radiolabelled 3,5-di-O-[14C]acetyl-4-O-(2,3,4,6-tetra-O-methyl-beta-D-galactopyranosyl )-2 , 6-di-O-methyl-D-glucose diethyl dithioacetal (7) and 5-O-[14C]acetyl-2,3,4-tri-O-methyl-L-fucose diethyl dithioacetal (8). The former was further degraded via the bis(sulfone), and thereby 2,3,4,6-tetra-O-methyl-D-galactose (13) was expelled. The monosaccharide branches, fucose and galactose, were identified as derivatives 8 and 13, respectively, by comparison with authentic samples. Isolation of microquantities of products was carried out by preparative TLC.