Synthesis, crystal structure, and reactivity of a D-xylose based oxepine

The synthesis and X-ray crystal structure of a D-xylose-based oxepine are reported. The oxepine was prepared from 2,3,4-tri-O-benzyl-D-xylose by the three-step sequence (Wittig olefination, vinyl ether formation, and ring closing metathesis) we recently reported. Epoxidation of this cyclic enol ether using dimethyldioxirane (DMDO) gave 1,2-anhydro-beta-D-idoseptanose, which was trapped by a number of nucleophiles to give alpha-idoseptanosides. The stereochemistry of epoxidation was assigned based on product analysis. Spectroscopic data of methyl 2,3,4,5-tetra-O-acetyl-alpha-D-idoseptanoside, derived from the methanolysis product 11, was compared to data of its enantiomer, the known methyl 2,3,4,5-tetra-O-acetyl-alpha-L-idoseptanoside.