Synthesis of 5-thio-D-xylopyranose

Taking this result into account, we have developed an efficient enzymatic route catalyzed by FruA in which the acceptor substrate is a commercially available 2-haloacetaldehydes (chloro- or bromo-) 19 yielding 5-halo-D-xylulose after dephosphorylation catalyzed by acid phosphatase (see Section 18.2.3.1). The thiol was introduced after the enzymatic step by displacement of halogen with NaSH, to 

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SCHEME 28.31. Transketolase-catalyzed synthesis of 5-thio-D-xylopyranose 75. 

Thio-D-xylopyranose has been the sugar of this type most thoroughly investigated. Its synthesis was reported in 1961, independently and simultaneously from three different laboratories. With sodium thiocyanate, l,2-0-isopropylidene-5-0-p-tolylsulfonyl-a-D-xylofuranose (211) gives a thiocyanate that reacts with sodium sulfide to give l,2-0-isopropylidene-5-thio-a-D-xylofuranose (212). A better synthesis is the treatment of 211 with sodium thiosulfate, followed by reduction of the resultant Bunte salt with sodium boro-hydride. The same compound 212 is obtained by nucleophilic replacement of the 5-sulfonyloxy group in 211 by treatment with potassium thioacetate followed by deacetylation to 212, or by the reaction of 211 with sodium a-toluenethioxide, followed by scission of the resultant S-benzyl compound with sodium in liquid ammonia. 

Bozo, E, Boros, S, Kuszmann, J, Gacs-Baitz, E, Parkanyi, L, An economic synthesis of 1,2,3,4-tetra-O-acetyl-5-thio-D-xylopyranose and its transformation into 4-substituted-phenyl 1,5-dithio-D-xylopyranosides possessing antithrombotic activity, Carbohydr. Res., 308, 297-310, 1998. 

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."" " ... 

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