A stereospecific approach towards the synthesis of 2-deoxy α- and β-glycosides based on a 1,2-ethyl (phenyl) thio group migration

Reactions of phenyl and ethyl 2-O-sulfonyl-1-thio-α-d-manno- and β-d-glucopyranosides with thionucleophiles

“…The b-anomeric configuration of compound 9 proves the latter mechanism, since the 1,2-thiomigration would result in inversion of the anomeric configuration via an episulfonium intermediate, or would afford an anomeric mixture via an oxocarbenium ion intermediate. 3,12 Treatment of 5 with MeSNa (5 equiv) in DMF at 50°C for 3 h resulted again in a 1,2-dithio compound (10), whose structure determination was performed similarly to that of compound 9. The observed data were as follows: [a] D +41.8; 1 J C1-H1 155.…”

“…The formation of compound 19 was assumed in an intramolecular 1,2-thiomigration reaction via an oxocarbenium intermediate. 3,12 This type of reaction would afford both anomers, however, we could isolate only the a-product.…”

Total synthesis of an antigenic heptasaccharide motif found in the cell-wall lipooligosaccharide of Mycobacterium gordonae strain 989

“…Selective 4-methoxybenzylation of ethyl 4,6-O-benzylidene-1-thio-β-D-glucopyranoside (4) [36] via stannylidene acetal formation [37] followed by conventional acetylation furnished ethyl 2-O-acetyl-4,6-O-benzylidene-3-O-(4-methoxybenzyl)-1-thio-β-D-glucopyranoside (5). Tin mediated [37] selective 4-methoxybenzylation of ethyl 4-O-benzyl-1-thio-α-L-rhamnopyranoside (6) [38] followed by acetylation furnished compound 7 in excellent yield. Compound 8 was also prepared from compound 6 in excellent yield following the similar reaction sequences except a base mediated methylation [39] in stead of acetylation.…”

Concise synthesis of a heptasaccharide antigen found in the cell-wall lipopolysaccharide of Mycobacterium gordonae strain 990

“…Ethyl 4-O-benzyl-2-O-(4-methoxybenzyl)-3-O-methyl-1-thio-α-L-rhamnopyranoside (6) was prepared from ethyl 4-O-benzyl-1-thio-α-L-rhamnopyranoside (8) [24] in excellent yield following a tin mediated selective methylation followed by 4-methoxybenzylation under alkaline conditions (Scheme 1).…”