Photodimerization in pyrimidine-substituted dipeptides

Ten N-epsilon-glycylornithineamide derivatives have been synthesized containing various N-alpha-linked pyrimidine-1-ylacetyl groups which can undergo (2 pi + 2 pi) photodimerization on irradiation with UV light at 254 rim. The dimerization efficiency of the free and bound pyrimidine groups was compared in aqueous solution: it was dependent on the substitution of the pyrimidine ring. N-alpha,N-alpha'-bis-(uracil-1-ylacetyl)-(N-epsilon-glycylomithineamide) and N-alpha,N-alpha'-bis-(5-bromouracil-1-ylacetyl)-(N-epsilon-glycylomithineamide) were identified as possible candidates for optical data storage.