Amino Acids and Peptides. XXX. Phosphorus in Organic Synthesis. XVII. Application of Diphenyl Phosphorazidate (DPPA) and Diethyl Phosphorocyanidate (DEPC) to Solid-phase Peptide Synthesis

Two coupling reagents for peptide synthesis, diphenyl phosphorazidate (DPPA) and diethyl phosphorocyanidate (DEPC), were tested using the solid-phase method. The reactivities of DPPA and DEPC were examined by coupling Boc-Ile with Gly-resin. In a comparison of these reagents with DCCD, these reagents showed higher reactivity than DCCD in DMF. The N-Boc derivative of melanocyte release inhibiting hormone was synthesized in good yield by the solid-phase method using these reagents. Racemization during fragment condensation on the polymer support was examined by coupling Boc-Gly-L-Ala with Leu-resin (Izumiya test).