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 of Ascochyta caulina, a promising mycoherbicide for biol. control of Chenopodium album. The metabolite, which shows interesting phytotoxic properties, together with ascaulitoxin (recently characterized as N2--D-glucoside of the unusual bis-amino acid 2,4,7-triamino-5-hydroxyoctandioc acid) and another unidentified compd., compose an active fraction of A. caulina culture filtrates with promising herbicidal properties. When assayed on leaves of host and nonhost dicots, including wild and cultivated plants, trans-4-aminoproline showed a wide range of toxicity, with leaves of C. album 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-aminoproline as naturally occurring compd. and phytotoxic metabolite produced by A. caulina.