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.
Keywords: amino acids; decarboxylation; electron transfer; photochemistry; phthalimides.