PyBroP (1) and PyCloP (21, two halotripyrrolidinophosphonium hexafluorophosphates, are peptidecoupling reagents highly efficient for coupling N-methylated amino esters, in contrast with PyBOP (3), the hydroxybenzotriazolyl analogue. These halogenophosphonium salts 1 and 2 are convenient (one-pot reactions) stable solids soluble in conventional solvents. Use of them gave an excellent peptide yield with essentially no epimerization. Activation with ...