| Abstract
| - Ab initio molecular orbital calculations have been used to studythe effect of ring distortion on the outcomeof protonation of 2-methoxyoxane and 2-methylsulfanyloxane in the gasphase. Protonation of the skewconformations of equatorial 2-methoxyoxane results in spontaneouscollapse to the oxocarbenium ion, whereasthe skew conformations of equatorialmethyl(2-oxanyl)sulfonium exist as stable species. Thechair conformationof the axial anomer of methyl(2-oxanyl)sulfonium is alsofound to exist as a stable species, unlike the axialanomer of methyl(2-oxanyl)oxonium, which collapsesspontaneously to the oxocarbenium ion. These resultsare discussed in relation to the stability of thioglycosides towardcleavage by glycosyl hydrolases.
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