Synthesis of fragments of human β‐lipotropin, β_h‐LPH. Part IV*. The synthesis of shortened peptides related to des‐1‐tyrosine‐γ‐endorphin [β‐LPH‐(62‐77)]

Abstract

Synthesis of fragments of human P-lipotropin, P,-LPH be obtained (as calculated from eq. 1) which correlate with the experimental peroxidation rate constants for many aromatic molecules over a range of more than eight orders of magnitude. For reasons not yet fully understood, the most serious exceptions are 9, I0-dimethylanthracene and di benzan thracene. Given such limitations, we feel that the present data show that a simple FMO approach gives a satisfactory description of the reactivity of singlet oxygen towards many aromatic molecules. Furthermore, the applicability of the FMO model confirms that the endoperoxidation is adequately described by a [4x + 2x]-cycloaddition mechanism and that the progress of bond formation in the transition state shows little dependence on the reactivity of the aromatic substrate. It seems unlikely that the alternative stepwise pathway for the addition of singlet oxygen to diene-systems, proposed by Detour C.S. 19, can explain the correlation between reaction rates and FMO energies. Abstract. The synthesis of several peptides related to P-LPH-(62-77) but shortened from the Nterminal end, is described. In these syntheses use has been made of the classical fragment condensation approach.