The behavior of two thiosugar thioglycosides towards oxidation

Oxidation of 4-cyanophenyl 2,5-anhydro-1,6-dithio---glucoseptanoside with magnesium monoperoxyphthalate (MMPP) resulted in a mixture containing two endo- and two exo-monosulfoxides as well as two endo-exo bis-sulfoxides differing in the chirality of the sulfoxide groups. Besides the aforementioned six products a further endo–exo bis-sulfoxide isomer as well as an exo-sulfone was obtained via oxidation with NaIO₄. Oxidation of 4-nitrophenyl 1,5-dithio-β--arabinopyranoside with MMPP yielded only two endo-sulfoxides, while oxidation with NaIO₄ in turn led to cleavage of the carbohydrate ring. The formed dialdehyde was stabilized by cyclisation to a hemiacetal, which on further treatment with MMPP afforded an exo-monosulfoxide. The position of oxidation as well as the chirality of the respective sulfoxide groups was established by NMR spectroscopy and X-ray crystallography.