ASYMMETRIC-SYNTHESIS OF THE KEY INTERMEDIATES LEADING TO (-)-APHANORPHINE AND (-)-EPTAZOCINE

The asymmetric syntheses of two key intermediates, 8 and 15, in >99% e e are reported. These compounds are prepared by diastereofacial additi on of lithiodimethylphenylsilane to chiral naphthyloxazolines followed by methyl iodide trapping. The two stereocenters are formed in greate r than 95% ds, and the silyl center is subsequently removed to give th e 1,1-disubstituted tetralins 8, 9, or 12. These chiral substances are readily transformed into the titled compounds as described in the lit erature. The absolute configuration of these intermediates has been co nfirmed by X-ray analysis and corrects an earlier misassignment.