Xylofuranose 1,2-0-isopropylidene-5-thio

The reaction of 5-amino-5-deoxy-l,2-0-isopropylidene-a-D-xylo-furanose (15) with methanolic hydrogen chloride (0.5 %), under careful exclusion of moisture, results in a mixture of the anomers of methyl 5-amino-5-deoxy-D-xylofuranoside, from which the /8-D anomer crystallizes. The five-membered ring-structure was proved by the results of periodate oxidation and by the infrared spectrum of the tetraacetate, which shows a band for NH. A methyl pyranoside was not found, and 3-pyridinol (21) was formed only in traces. A spontaneous ring-enlargement, such as is observed under similar conditions with 1,2-O-isopropylidene-5-thio-a-D-xylofuranose (see p. 208), is not possible in this instance. Stabilization as the methyl fiiranoside is, apparently, so rapid that the secondary reaction (leading to the pyranose form) does not occur. If water (several percent) is added to the reaction mixture, glycoside formation is hindered, and a large proportion of 3-pyridinol is formed. ... 

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. 

Methanolic hydrogen chloride converts 1,2-0-isopropylidene-5-thio-a-D-xylofuranose into a crystalline glycoside formulated as the a-D-pyrano-side (124) which releases one equivalent of formic acid per mole on... 

Acetamido 4-deoxy-l,2-0-isopropylidene-a-D-xylofuranose, A-357 4-Acetamido-4-deoxy-5-thio-L-Iyxopyranose, A-3 4-Acetamido-2,3-di-0-acetyI-l,6-anhydro-4-deoxy-p-D-mannopyranose, A-314... 

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