Highly stereoselective intramolecular a-arylation of self-stabilized non-racemic enolates: synthesis of a-quaternary a-amino acid derivatives.

The one-pot stereoselective conversion of N-(4-nitrobenzene)sulfonyl-a-amino acid tert-Bu esters into the corresponding N-alkyl-a-(4-nitrophenyl)-a-amino esters has been realized through N-alkylation of the starting amido esters, followed by N-Ca migration of the p-nitrophenyl group and the loss of sulfur dioxide; the asym. induction is detd. by an intermediate non-racemic enolate, without the need of an external source of chirality.