The Anaerobic Photolysis of Tryptophan Containing Peptides—ii

A number of trp–containing peptides (gly‐ l ‐trp, l ‐ala‐ l ‐trp, l ‐trp‐gly and N‐acetyl‐trp) have been photolyzed under anaerobic conditions. Analysis of the resultant photoproduct mixtures suggests the intermediacy of an hydrated electron in the case of trp‐gly and N‐acetyl‐trp. Amino acid trp peptides deaminate with a concomitant cyclization to the 4‐position of the indole. This appears to occur via a short‐lived radical indole complex. Little difference was detected between photoproduct mixtures using either vycor or a Corning CS‐0‐54 (cut off ca. 295 nm) as filters. Thus these reactions can occur both above and below the ionization point of trp.