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

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. R 1 = H, Me, Et.