ENANTIOSELECTIVE LITHIATION AND SUBSTITUTION OF (E)-CINNAMYL N,N-DIISOPROPYLCARBAMATE THROUGH USE OF (-)-SPARTEINE COMPLEXES

The title reaction leads to diastereomeric lithium carbanion pairs tha t are configurationally unstable and equilibrate even at temperatures below -50 degrees C. The initially formed epimer (1S)-epi-10 is rapidl y converted to the thermodynamically more stable (1R)-10 (in toluene s olution). Carboxylation, acylation with acid chlorides, stannylation, and silylation take place at the alpha-position with stereoinversion ( 79-86% ee). Methylating agents attack the gamma-position; here, the st ereochemical course depends an the leaving group, anti-S-E, for the io dide (50% ee) and syn-S-E, (48% ee) for the tosylate.