Synthesis of γ-Oxo-α,β-dehydro-α-amino Acids from N-tert-Butyloxycarbonyl-α-Imino Esters and Carbonylmethyl 2-Pyridinylsulfones via an Mannich-Elimination Cascade

A method for facile synthesis of γ-oxo-α,β-dehydro-α-amino acids has been developed. The process involves a triethylamine-mediated Mannich-elimination cascade process from N-tert-butyloxycarbonyl (Boc)-α-imino esters with carbonylmethyl 2-pyridinylsulfones. The γ-oxo-α,β-dehydro-α-amino acids are produced in good yields of 51-98% and with excellent E selectivity. The γ-oxo-α,β-dehydro-α-amino acid derivatives can be conveniently transformed to highly enantioenriched α-amino acids via an asymmetric hydrogenation. Want- E? A triethylamine-mediated Mannich-elimination cascade process from N-tert-butyloxycarbonyl (Boc)-α-imino esters with carbonylmethyl 2-pyridinylsulfones for the synthesis of γ-oxo-α,β-dehydro-α-amino acids is reported. The γ-oxo-α,β-dehydro-α-amino acids are produced in good yields and with excellent E selectivity, and can be conveniently transformed into highly enantioenriched α-amino acids via an asymmetric hydrogenation.