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.