Synthesis of the thio-linked ganglioside GM3 epitope

Article abstract of DOI:10.1002/jlac.199719970512

The synthesis of sulfur-linked GM₃ epitope 2 is based on acid-catalyzed and base-promoted S-glycosylation processes. As a precursor, 2-O-benzoyl-3-thiogalactoside 10 was required, and was obtained from 4,6-O-benzylidene-galactoside 3 in six high-yielding steps. Base-promoted S-glycosylation of 10 with neuraminic acid functionalized β-halogenose 11 in the presence of NaH as base and Kryptofix 21 as coactivator afforded α(2-3)-thio-linked disaccharide 13, which was readily converted to α-halogenose 20. Heptyl 1-thioglycoside 22 was obtained from O-galactosyl trichloroacetimidate 21 and heptylthiol via acid-catalyzed S-glycosylation. 22 was transformed into 2,3,6-tri-O-acylgalactoside 26 which, via the 4-O-triflate and treatment with potassium thioacetate, followed by selective removal of the S-acetyl group, furnished the 2,3,6-tri-O-acyl-4-thioglucoside 28. Base-promoted S-glycosylation of 28 with halogenose 20 led to fully acylated target molecule 29, which was quantitatively converted into 2. VCH Verlagsgesellschaft mbH, 1997.