Spectral analysis of a series of partially protected and deprotected tetrapeptides, analogues of AS-I phytotoxin

A series of six tetrapeptides, analogues of AS-I phytotoxin, pathogenic to sunflower, have been synthesized either in solution and/or by solid phase m ethods and have been tested for phytotoxic activity in various plants and c ytotoxic activity in three cancer cell lines. These peptides were identifie d as model compounds by fast atom bombardment (FAB), plasma desorption (PD) , electrospray ionization (ESI) mass spectrometry and by H-1, H-1-H-1, C-13 and H-1-C-13 NMR. The data presented show that in protected tetrapeptides the molecular ion was easily identified whereas some difficulties appeared with the fully deprotected peptides. NMR spectra are given.