Thioglucosides

Note The detection limit for aryl- and thioglucosides is 100 — 200 ng substance per chromatogram zone [2]. Reduction of the proportion of phosphoric acid in the reagent leads to loss of sensitivity [2]. 

Thioflavine, pH-dependent change of fluorescence color 91 Thioglucosides 185,186 Thioglycolic acid 248, 249... 

Access to P-mannosides [209] is illustrated by the preparation of 179 from P-glucoside 178 by oxidation of the equatorial 2-OH followed by stereoselective reduction to give the axial alcohol an efficient indirect route to the a-mannosides [206] utilizes the P-thioglucoside 182, readily obtained from epoxide 173, proceeding via an oxidation-reduction protection sequence to give P-thiomannoside glycosyl donor 184, from which a-mannoside 185 can be stereoselectively prepared. 

Because of the fraction in which the inhibitor(s) were present, the allelochemicals in campestris are most likely isothiocyanate derivatives such as allyl isothiocyanate, a breakdown product of the thioglucoside, sinigrin (21). 

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),... 

When acetobromoglucose was dissolved in ether, and treated with an aqueous, alkaline solution of benzenethiol, phenyl 1-thioglucoside was obtained acetobromolactose was also utilized successfully in this type of synthesis. 

Ogawa and co-workers [97] have synthesised the complete glycosphingolipid (361) containing the terminal tetrasaccharide (356) of the Leb antigen attached to lactosyl ceramide. The lactose derivative (95), prepared by the action of trimethylamine — borane and aluminium chloride [99] on the benzylidene derivative (94), was condensed with the thioglucoside (362) in the presence of methyl triflate and molecular sieve to give the trisaccharide (363). This was deacetylated and the product (364) condensed... 

SCHEME 2.30 Orthogonal protection of the thioglucoside 107 via acetal and ketal ring... 

Activation of thioglucosides. Thioglucosides are useful for glycosidation since they are more reactive than glycosyl halides. They are known to be activated by methyl triflate, but this triflate is a potent carcinogen. Methylsulfenyl trifluoromethanesulfonate (1) is also an activator and has the advantage that it can be prepared in situ. Thus the 1-thio-p-D-glucopyranoside (p—2) couples with a-D-... 

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