The Photochemistry of <i>N</i>‐Phthaloyl α‐Amino Acid Esters: A New Approach to β,γ‐Unsaturated α‐Amino Acids and Dihydrobenzazepinediones

Abstract

Interesting as enzyme inhibitors, β,γ-unsaturated α-amino acids can be synthesized by irradiation of the corresponding N-phthaloyl methyl ester [Reaction (a)]. Apart from this reaction, two further reaction pathways are observed (except in the case of the valine derivative): In the absence of γ H atoms, as in the tert-leucine derivative, the 1,5-diradical cyclization and the formation of dihydrobenzazepinedione carboxylate, presumably via an ϵ-Norrish type II intermediate. R1 = H, Me, Et.