Asymmetric synthesis of α,α-disubstituted amino acids by diastereoselective functionalization of enantiopure phenyloxazinones, derivatives of asymmetric Strecker reaction products of aldehydes

Esterification of the asymmetric Strecker reaction products of a suitable aldehyde and (R)-phenylglycinol followed by lactonization and alkylation provides chiral oxazinones 5. Treatment of the enolates of 5 with active alkyl halides, or aldehydes provided the corresponding functionalization products with high diastereoselectivity. The configuration of newly created quaternary carbon is S for the products coupled with simple alkyl halides and aldehydes, and R for the products coupled with methyl bromoacetate. Deprotection of these products afforded the corresponding enantiopure α,α-dialkyl amino acids.