Organophosphorus esters 9, 10, 14, and 15 prepared via reaction of diethyl-and diphenylphosphoryl chloride, di (o-tolyl) phosphinyl chloride, and 2, 8- dimethylphenoxaphosphinyl chloride with HOAt are excellent coupling reagents for peptide synthesis which are generally superior to their uronium/guanidinium analogues and HOBt-or HODhbt-derived phosphate ester counterparts in minimizing loss of configuration during ...