Glycosides thio, synthesis

An improved method for the synthesis of a-fucosyl (l- 3)-3-thio-glycoside (65 c) involved the nucleophilic displacement of a cyclic sulfamidate derived from allosamine (67). The regioselective opening of (67) with (30b) led to (65c) in good yield (Scheme 21) [51]. 

The first synthesis of methyl 4-thiomaltoside (36b) (34%), 4-thiocellobioside (39d) (52%) and 4-thiodigalactobioside (86) (56%) was reported 18 years ago by using the Sn2 displacement of 1,2-cis- or 1,2-trans- glycosyl halides (9 a), (7 a) and (7c) with methyl 4-thio-a-D-glycopyranoside sodium salts generated from the acetylated methyl glycosides (84) and (85a) (Scheme 25) [14a]. 

Ethyl l-thio-/3-maltoside heptaaeetate (59) has proved to be a useful intermediate in the synthesis of the a-glycoside of maltose (see Section III).30 Treatment of /3-maltose octaacetate with ethanethiol and fused zinc chloride gave compound 59 in 83% yield. Synthesis of mal-... 

A. Hasegawa, J. Nakamura, and M. Kiso, Synthesis of alkyl ot-glycosides of 2-thio-W-acetylneuraminic acid, J. Carbohydr. Chem. 5 11 (1986). 

For an example of glycoside synthesis with 0-benzylated 2-benzothiazolyl-1-thio-D-gluco-pyranoside in the presence of Cu(OTf)2, see T. Mukaiyama, T. Nakatsuka, and S. Shoda, An efficient glucosylation of alcohol using 1-thioglucoside derivative, Chem. Lett. p. 87 (1979),... 

Sulfides are hydrogenolyzed usually by Ra-Ni.383-391 Phenyl and methylthio groups were removed by Ra-Ni (10 mmol Ni/mmol) refluxing in ethanol for 2 hours.392 A thio enol ether was desulfurized with Ra-Ni (100 mmol Ni/mmol) in MeOH at room temperature for 30 minutes.393 During the synthesis of 2-deoxy-P-glycosides the removal of the arylthio group was achieved using Ra-Ni with no problem.394... 

The synthesis of 4 and 5 provided an opportunity to evaluate the scope of a new C-glycosidation methodology that was used for 3 (28-34). Accordingly, esterification (step A) of the glycone component, l-thio-l,2-0-isopropylidene acetal (TIA) 16 and one or the other aglycone segments, C-branched saccharide acids 14 or 15, furnishes ester 12 or 13, respectively (Scheme 1). Tebbe methylenation (step B) of the latter provides enol ethers 10 or 11. Thiol... 

Hummel and Hindsgaulfel developed a solid-phase synthesis of thio-oligosac-charides exemplified by the synthesis of the trisaccharide 31,5 [Scheme 531], which features the use of a disulfide to protect an anomeric thiol. The method exploits a highly reactive sugar thiolate 31,1 devoid of protecting groups as the nucleophile in a displacement reaction on triflate-activated glycoside 31,2 The... 

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