Glycoside phenylthio

The anomeric proton in phenylthio 2,3-dideoxy-hex-2-enopyranosides is sufficiently acidic to enable deprotonation and, for example, reaction of S-glyco-side 68 with BuLi leads to dianion 69 which alkylates or acylates at C (1) from the a-face to give C-glycosides 70 (Scheme 17) [24]. Similarly, deprotonation of hex-2-enopyranoside 71 and coupling with cyclic sulfate 72 provides alkylated product 73 which, upon hydrolysis at pH > 3.5, undergoes a loss of sulfate and a... 

Thioglycosides were first introduced in glycosidation reactions by Ferrier in 1973 [31], who used the ethylthio group at the anomeric position. Subsequently, Hanessian [32] demonstrated the usefulness of the 2-pyridylthiol. Currently, the phenylthio and the ethylthio carbohydrate derivatives are the most commonly used glycosyl donors from this class of... 

Protic acids will also cleave p-methoxy benzyl ethers under comparatively mild conditions. At 90 cC, acetic acid is sufficient352 but the reaction works at room temperature with as little as 0.5% trifluoroacetic acid in dichloromethane.353 p-Methoxybenzyl groups can be removed selectively with trifluoroacetic acid in the presence of secondary glycosidic linkages, azides, or phenylthio glycosides [Scheme 4.189],354 The survival of a trisaccharide under the deprotection conditions indicates that p-methoxybenzyl groups may be useful in oligosaccharide synthesis. 

SCHEME 4.58 Synthesis of 2-deoxy-2-phenylthio glycoside using bis(arylthio)sulfonium salt promoter. 

The first total synthesis of the nucleoside antibiotic herbicidin B was accomplished in the laboratory of A. Matsuda. The key step was a novel aldol-type C-glycosidation reaction promoted by Sml2 between a 1-phenylthio-2-ulose derivative and a 1- 3-D-xylosyladenine-5 -aldehyde derivative. During the preparation of the phenylthio sugar subunit, the Moffatt oxidation was applied to convert the primary alcohol to the corresponding aldehyde, which was immediately oxidized with PDC in DMF/MeOH to the methyl ester. The reaction conditions were completely compatible with the silyl protecting group as well as the thioacetal functionality. 

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