Synthesis, separation and configuration determination of diastereoisomers of (R,S)-1-methyl-3-[3-(aryl)-1,2,4-oxadiazol-5-yl] propyl 2,3-dideoxy-α-d-erythro-hex-2-enopyranosides

For synthesizing title compounds, first we carried out the Ferrierʹs rearrangement involving tri-O-acetyl-d-glucal and alcohols using Montmorillonite K-10 as a catalyst. This reaction gave diastereoisomeric mixture of and . Basic hydrolysis of each pair of diastereoisomeric mixture furnished title compounds and , which were separated very carefully over a silica gel column yielding all diastereoisomers in the pure form. One of them was subjected to a single crystal X-ray analysis to determine the correct configuration at the asymmetric carbon atom of the aglycone. The methyl signals of the diastereomers helped to assign the configuration of each diastereoisomer. Molecular orbital calculations of using the semi-empirical method (AM1) has been performed to compare its results with the crystallographic data. We have also determined the rotational barrier of C(8) and O(9) bond in both (R) and (S) enantiomers of compounds and .