Photoinduced electron-transfer chemistry of the bielectrophoric N-phthaloyl derivatives of the amino acids tyrosine, histidine and tryptophan

The photochemistry of phthalimide derivatives of the electron-rich amino acids tyrosine, histidine and tryptophan 8–10 was studied with respect to photoinduced electron-transfer (PET) induced decarboxylation and Norrish II bond cleavage. Whereas exclusive photodecarboxylation of the tyrosine substrate 8 was observed, the histidine compound 9 resulted in a mixture of histamine and preferential Norrish cleavage. The tryptophan derivative 10 is photochemically inert and shows preferential decarboxylation only when induced by intermolecular PET.