| Popis: |
The influence was examined of representative bifunctional catalysts on racemization in peptide syntheses via aminolysis of cyanomethyl, p-nitrophenyl, thiophenyl, and vinyl esters. Three different tests were used, based on gravimetric, polarimetric, and gas-liquid chromatographic analysis, respectively. 1,2,4-Triazole, which was investigated most extensively, did not cause racemization in any of the couplings. Imidazole, which has also been recommended for acceleration of peptide syntheses, led to racemization in several cases. The structure of N-acyl derivatives of 1,2,3- and 1,2,4-triazole was determined by proton resonance measurements. |
