Isolation of a sultone as an unusual acetolysis product

Acetolysis of methyl 5,6-di-O-acetyl-2,3-O-isopropylidene-β-l-gulofuranoside has yielded a sultone, 4-(1,2,5,6-tetra-O-acetyl-β-l-gulofuranos-3-yl)-6-methyl-1,2-oxathiin 2,2-dioxide (2) whose structure was determined by X-ray diffraction. 1H and 13C NMR spectral properties of 2 are presented together with a rationale for its formation. Preparation and properties of the related α-d-mannofuranos-3-yl compound 4 are described.