Oxazinones, asymmetric alkylation reaction

D-Glucose-derived oxazinones, which can be considered as chiral glycine derivatives, were also employed in asymmetric alkylation reactions [155]. The oxazinone represents a rigid... 

SCHEME 10.70 Chiral glycine derivatives such as d-glucose-derived oxazinones are useful in asymmetric alkylation reactions. 

Asymmetric nthesis of N-methyl-a-amino esters This morpholine can be used as a chiral template for synthesis of N-methyl-a-amino esters. Thus reaction with an alkylcopper involves displacement of the phenylthio group by an alkyl group by the usual Sn2 process with inversion (about 90 10). In contrast, reaction with an alkylzinc iodide involves substitution with essentially complete retention, possibly via an iminium intermediate. The alkylated product (2) is then oxidized to an oxazinone (3), which on treatment with vinyl chloroformate followed by hydrolysis provides N-methyl-a-amino esters (4) in high optical purity. This approach to chiral amino acids is unusual in that either enantiomer can be formed from the same template depending on the choice of the organometallic reagent. Unfortunately, the chiral auxiliary (expensive) is not recovered for reuse. 

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