Novel 2,3-unsaturated O-glycosides containing an alkynyl function in their aglycones

This paper describes the synthesis of seven D-glucosides, 3a-g, and six D-galactosides, 4a-f, all containing an alkynyl function in their aglycones. The reaction was performed using dichloromethane as solvent in the presence of Montmorillonite K-10. The structure of all compounds were confirmed employing IR, 1 H NMR and 13 C NMR spectroscopic techniques. The aim was to study their conformational energies using ab initio Hartree Fock method with 6-31G as basis set. Two compounds, namely, ( R )-(+)-3-butyn-2-yl 4,6-di- O -acetyl-2,3-dideoxy-α-D- erythro -hex-2-enopyranoside, 3d, and ( R )-(+)-3-butyn-2-yl 4,6-di- O -acetyl-2,3-dideoxy-α-D- threo -hex-2-enopyranoside, 4d, were subjected to X-ray diffraction analyses and their experimental values compared with the calculated values obtained by molecular orbital calculations. Our studies have found a good correlation between the two types of glycosides.