A PULSE-RADIOLYSIS STUDY OF ONE-ELECTRON OXIDATION AND CENTER-DOT-OH RADICAL REACTION OF A NEW CLASS OF ANTIOXIDANTS - 2,5-DIMETHYLPYRROLE AMINO-ACID N-CONJUGATES

A new class of 2,5 dimethylpyrrole functionalized amino acid and pepti de antioxidants has been synthesized. Pulse radiolysis studies have be en carried out on these compounds to determine their reactivity in one -electron oxidation reactions with Br-2(-) and (SCN)(2)(-) as well as their reactivity toward the water radicals (OH)-O-. and e(aq)(-). When compared to similar reactions with parent amino acids and peptides, b oth rate constants and transient spectra indicate considerable interac tion between the electronic states of the pyrrole moiety and amino aci d or peptide. Where comparison data is available, radical reactions ar e significantly more rapid with these derivatives than with the parent compounds. Exceptions occur in some cases of (OH)-O-. attack where st eric hindrance may be evoked to explain a lower rate constant in the d erivative compounds. Electron attachment rates are also found to be en hanced by the presence of the pyrrole ring.