Are α-centered peptide radicals stabilized by a capto-dative effect?

Article abstract of DOI:10.1016/S0040-4039(97)10085-5

The kinetics of the thermal C-C-cleavage reaction of the dimer of sarcosine anhydride 5 has been investigated between 295 and 333 °C in mesitylene. From the temperature dependence and from the release of strain on dissociation the cyclic α-peptide radical 6 was calculated to have a radical stabilization enthalpy (RSE) of -6.3 ± 1.3 kcal / mol thus indicating the absence of a synergistic capto-dative effect.