<p></p> <p>Methyl 3,5-anhydro-3-thiopentofuranosides (“3,5-Thietanopentosides”) of the D-<i>xylo</i>, L-<i>lyxo</i> and 2-deoxy-D-<i>threo</i> series were oxidized to the corresponding <i>S</i>-oxides (sulfoxides) and/or <i>S,S</i>-dioxides (sulfones) by use of hydrogen peroxide or <i>meta</i>-chloroperbenzoic acid. The diastereoisomers resulting from the additional chiral sulfur center in the sulfoxides could be separated. Their configuration was assigned by NMR spectroscopy and in one case unequivocally corroborated by an X-ray structure analysis. The observed stereoselectivity of the oxidation can be attributed to the specific steric requirements in the different thietano sugars. X-Ray structural analyses of three crystalline sulfones were also performed. Attempts to generate carbanions of the sulfoxides and sulfones and to use these for reactions with electrophiles were not successful.</p
