Studies on the ß-Turn of Peptides. II. Syntheses and Conformational Properties of N-(2,4-Dinitrophenyl)tetrapeptide p-Nitroanilides Related to the ß-Turn Part of Gramicidin S

N-(2,4-Dinitrophenyl)tetrapeptide p-nitroanilides related to the ß-turn part of gramicidin S were synthesized and subjected to CD measurements. The ß-turn preference of the tetrapeptide derivatives had correlation with the antibiotic activities of the gramicidin S analogs containing similar tetrapeptide sequences at their ß-turn part. So, conformational preference of partial sequences of gramicidin S analogs seem to play a significant role for determining their biological activities.