Yaping Hong, R. Bakale, Q. Fang
Dec 1, 2000
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Journal
Tetrahedron-asymmetry
Abstract
Abstract Two synthetic methods have been established for the preparation of enantiomerically pure desmethylzopiclone, a metabolite of zopiclone. In Method A, (S)-desmethylzopiclone was prepared by demethylation of (S)-zopiclone with 1-chloroethyl chloroformate in high yield. Enantiomerically pure zopiclone (>99% ee) was obtained through a highly efficient resolution process in >36% overall yield. In Method B, racemic desmethylzopiclone was resolved with l -N-benzyloxycarbonyl phenylalanine ( l -ZPA) followed by recrystallization in good yield. The absolute stereochemistry of the (+)-enantiomer was first determined to be the (S)-configuration by X-ray crystallography.