SYNTHESIS AND ISOMERIZATION OF OPTICAL ACTIVE 2-[(6,7,8,9-TETRAHYDRO-5H-CYCLOHEPTA[B]PYRIDIN-9-YL)SULFINYL]-1H-BENZIMIDAZOLE ANALOGS

Four stereoisomers, (Rs,9R)-(+)-5, (Ss,9R)-(-)-5, (Ss,9S)-(-)-5 and (Rs,9S)-(+)-5, were prepared from optically active (R)-(+)-3 and (S)-(-)-3, and their absolute structures were unambiguously determined by X-ray crystallographic analysis of (Ss,9R)-(-)-5. Epimerization of the carbon bearing the sulfinyl group of 5 could be carried out with NaOCH3. At the same time, it was found that the stereochemistries of the sulfinyl group of (Rs,9R)-(+)-5 and (Ss,9S)-(-)-5 were spontaneously inverted in MeOH solution at room temperature.