Abstract
The synthesis of sulfur‐linked GM~3~ 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.