The photochemistry of N-p-toluenesulfonyl peptides: the peptide bond as an electron donor

The scope of photobiological processes that involve absorbers within a protein matrix may be limited by the vulnerability of the peptide group to attack by highly reactive redox centers consequent upon electronic excitation. We have explored the nature of this vulnerability by undertaking comprehensive product analyses of aqueous photolysates of 12 N-p-toluene-sulfonyl peptides with systematically selected structures. The results indicate that degradation includes a major pathway that is initiated by intramolecular electron transfer in which the peptide bond serves as electron donor, and the data support the likelihood of a relay process in dipeptide derivatives

N-pyrrolyl phosphines : enhanced π-acceptor character via carboalkoxy substitution

A series of 3,4-dicarboethoxy-N-pyrrolyl phosphine ligands (R2P-NC4H2(CO2Et)(2)) is described. A number of techniques, including reaction calorimetry, infrared spectroscopy, and X-ray crystallography, demonstrate that these ligands are potent pi-acceptors and that the electronic substituent parameter chi(i) for the 3,4-(EtO2C)(2)C4H2N moiety is ca. 16, placing it in a position between fluorine and chlorine