Trans-4-aminoproline, a phytotoxic metabolite with herbicidal activity produced by Ascochyta caulina

A phytotoxic metabolite, characterized through NMR techniques and synthetic methods as trans-4-aminoproline, was isolated from the culture filtrates o f Ascochyta caulina, a promising mycoherbicide for biological control of Ch enopodium album. The metabolite, which shows interesting phytotoxic propert ies, together with ascaulitoxin (recently characterized as N-2-beta-D-gluco side of the unusual bis-amino acid 2,4,7-triamino-5-hydroxyoctandioc acid) and another unidentified compound, compose an active fraction of A. caulina culture filtrates with promising herbicidal properties. When assayed on le aves of host and non host dicots, including wild and cultivated plants, the trans-4-aminoproline showed a wide range of toxicity, with leaves of C. al bum being the most sensitive. Other interesting aspects were its inefficacy on several monocots, both cultivated and wild and its lack of antifungal, antibiotic and zootoxic activities. This is the first report on trans-4-ami noproline as naturally occurring compound and phytotoxic metabolite produce d by A. caulina. (C) 2000 Elsevier Science Ltd. All rights reserved.