Comparative Study of Selected Coupling Reagents in Dipeptide Synthesis

A comparative study of the effectiveness of selected coupling reagents in dipeptide synthesis was conducted. Included in the study were a new coupling reagent, pentafluorophenyl diphenylphosphinate (FDPP, 1), benzotriazol-1-yl-oxytris(dimethylamino) phosphonium hexafluorophosphate (BOP, 2), 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (HBTU, 3), and isobutyl chloroformate (IBCF, 4). We found that BOP (2) afforded the highest yields and lowest limits of racemization.