Thioacetals pyranosides

The synthesis of 3-azido-3-deoxy-5-tliio-/i-D-ribopyranose (288) was realized" from the tosylate 286 via thioacetate 287 in five steps (Scheme 76). Treatment of287 with acidic methanol gave a septarable 1 2 mixture of the methyl a-and / -pyranosides. The a anomer 288, whose H NMR. spectrum suggested an equilibrium of the C4 and " Q conformations, was transformed into 289 by conventional reactions. l,2,3-Tri-6 -acetyl-3-azido-3-deoxy-5-thio-D-xylopyranose was prepared via the xylo analogue of 286, starting form D-glucose."" " ... 

The 3-thioacetate 17 has been obtained by opening of the cyclic sulfamidate 16, which was formed on exposure of the cis-vicinal hydroxy acetamide 15 to 1,T-sulfonyldiimidazole. Regioselective opening of benzyl 2,3-anhydro-a-D-ribo-pyranoside gave access to benzyl 3-(phenylthio)-a-D-xyloside (18). The 3-thio-and 6-thio-analogues 20 and 21, respectively, of amiprilose (19), have been synthesized by standard methods.3,6-Thio-anhydro-D-glucose derivatives 24... 

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