Studies on Photocleavage Reaction of Arylmethyl and Diarylmethyl Carboxylates

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1. Photolysis under Ar of diarylmethyl carboxylates, except for aromatic carboxylates, generally gives a diaryl ketone and a diarylmethanol Diarymethyl radicals formed by homolytic cleavage of C-0CO bond (beta-cleavage) quite efficiently trap trace amount of oxygen present in the reaction media under Ar to give the ketone and alcohol. At the same time, the reaction of oxygen with the alkyl radical derived from decarboxylation of the acyloxy radical gives an aldehyde or ketone. Cleavage of O-CO bond (alpha-cleavage) is concluded not to take place. High efficiency of oxygen trapping by diarylmethyl radicals is related to their stability and bulkiness by the product studies of photolysis of several diarylmethyl carboxylates. alpha- (1-Naphthyl) benzyl and 3,4-benzofluorenyl radicals are above all most efficiently trap oxygen.2. Application of this oxygen trapping reaction to the synthesis of an aldehyde from a carboxylic acid has not been successful.3. Fluorescence quenching exciplex formation in 2- (1-pyrenyl) ethyl p-cyanobnzoate was studied in detail, especially the effect of solvent polarity has been studied systematically for the first time.4. Efficient and convenient procedure for the protection of amino and phosphate groups has established. Various kinds of protected amino acids, peptides and phosphates are made by this procedure and their deprotection by irradiation was examined. (1-Pyrenyl) methyl was found not to be good for biological application because it decreases the solubility in water. More water soluble cinnnamoyl and 4-chmarinylmethyl are introduced to Leu-Leu-OMe and cAMP as caged groups and their in vitro photolytic behavier was studied.