THE STEREOSPECIFIC SYNTHESIS OF (-)-(8R) AND (-)-(8S)-METHYLCANADINE

Article abstract of DOI:10.1016/S0040-4020(01)85104-8

Regioselective complexation of the dimethoxy arene ring of canadine to the Cr(CO)3,moiety gives two diastereoisomers which are separated by flash chromatography.Deprotonation of either diastereoisomer with n-butyllithium followed by addition of methyl iodide or trimethylsilyl chloride gives C11-methyl- or -trimethylsilylcanadine after decomplexation.Each diastereoisomer of the C11-trimethylsilylcanadine complex may be treated with base and methyl iodide to give, after desilylation and decomplexation, the enantiomerically pure (-)-(8R) and (-)-(8S) methyl canadines; racemic samples of C8-methylcanadines are prepared via an independent route.