Synthesis and geometry of methyl (methyl 4-O-acetyl-3-azido-2,3-dideoxy-α/β-d-arabino- and -α/β-d-ribo-hexopyranosid)uronates

The synthesis of methyl (methyl 4-O-acetyl-3-azido-2,3-dideoxy-α/β-d-arabino- and -α/β-d-ribo-hexopyranosid)uronates is presented. High resolution 1H and 13C NMR spectral data for all diastereoisomers and single-crystal X-ray diffraction analysis for methyl (methyl 3-azido-2,3-dideoxy-β-d-arabino-hexopyranosid)uronate are reported. The planarity of the 4-OAc and 5-COOMe groups as well as the orientations of the aglycone and azide groups in the crystal lattice is discussed. The influence of the 5-COOMe group on the pyranose ring conformation is considered.