Xylofuranoside methyl 5-thio

C-3 in the unsubstituted compound.176,177 However, at the time of these experiments, only C-3 substitution had been observed with 2,3-anhydropentofuranosides, and the results of investigation of this reaction suggest that the amino sugar substituted at C-2 is the major product.184 With thiocyanate ion, substitution also occurs at C-3, leading to the thietane derivative, namely, methyl 3,5-anhydro-3-thio-a-D-xylofuranoside (59) but, as this compound was obtained in only 25% yield, the major pathway may involve 2-substitution, leading to products not characterized.178... 

Methyl 3,5-anhydro-3-thio-/3-D-xylofuranoside was oxidized with hydrogen peroxide to a mixture of the endo-sulfoxide, the -sulfoxide and the sulfone. Only the methyl 3,5-anhydro-3-thio-/ -D-xylofuranoside. V,.V-dioxidc could be isolated from the mixture by column chromatography in the pure crystalline form in 34% yield <2004CAR1787>. Treatment of spirocyclic thietane 25 (R = Me) with 2 equiv of w-chloropcrbcnzoic acid (MCPBA) yielded the sultine 30 in 54% yield (Equation 6) <1999J(P1)1151, 2002HCA2383>. 

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. ... 

Prediction of the composition of the equilibrium mixture on the basis of presumed conformational stability or instability is uncertain, as is shown by the example of 2,5-bis(acetamido)-2,5-dideoxy-D-xylose, obtainable by periodate cleavage of 3,6-bis(acetamido)-3,6-dideoxy-D-gulopyranose. From the reaction mixture, 2,5-bis(acet-amido)-2,5-dideoxy-D-xylofuranose can be obtained crystalline in 36% yield no report was made as to any content of pyranose. Other 5-acetamido-5-deoxyxylose derivatives, for example, methyl 3,5-bis(acetamido)-2-S-benzyl-3,5-dideoxy-2-thio-/3-D-xylofuranoside," were not susceptible to hydrolysis. ... 

As an example, the reaction of methyl 3-/S-ethyl-3-thio- 8-D-xylofuranoside (291) with methanesulfonyl chloride (or p-toluenesulfonyl chloride) gave a monochloro, monosulfonate derivative, formulatedi as the mixture (295). 

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