Metabolites Produced by the Phytopathogenic Fungus Rhizoctonia solani: Isolation, Chemical Structure Determination, Syntheses and Bioactivity

The isolation, structure determination, syntheses and biological activity of Nb-acetyltryptamine and three proline containing dioxopiperazines, cyclo(S-Pro-S-Leu) (2), cyclo(S-Pro-S-Ile) (3), and cyclo(S-Pro-S-Val) (4), from cultures of Rhizoctonia solani Kuhn are reported here for the first time. Despite the small amounts isolated, the absolute stereochemistry of these naturally occurring dioxopiperazines was established by 1H NMR using for the first time the chiral solvating agent (R)-(-)-2,2,2-trifluoro-1-(9-anthryl)ethanol.