CHELATE-CONTROLLED ASYMMETRIC-SYNTHESIS OF 2-SUBSTITUTED 2,3-DIHYDROPYRIDIN-4(1H)-ONES - SYNTHESIS OF D-AMINODEOXYALTROSE AND L-AMINODEOXYALTROSE DERIVATIVES

Asymmetric methylation and phenylation of the chiral pyridinium salt 7 , as well as methylation of chiral pyridinium salt 18, with Grignard r eagents occurred in good yield and with good-to-excellent diastereosel ectivities (Schemes 2 and 3, resp.). These results are best explained by assuming chelate control to govern the asymmetric alkylation/arylat ion process. The minimum-energy conformations of the out-of-plane twis ted pyridinium salts 7 and 18, as determined by the 'Molecular Simulat ions Cerius-Dreiding II' program, are in good agreement with the postu lated asymmetric chelate-control mechanism.