Synthesis and fungicidal activity of novel pimprinine analogues.

A simple and efficient synthetic protocol for 5-(3-indolyl)-oxazoles has been developed and further used to synthesize a series of novel analogues of natural product pimprinine. All new compounds were identified by (1)H NMR, high resolution mass spectrometry, and the structures of 10 and 18o were further confirmed by X-ray crystallographic diffraction analysis. Bioassay conducted at Syngenta showed that several of the synthesized compounds exhibited fungicidal activity. Compounds 10, 17, 18 h, 18o, 19 h, 19i and 19 l all showed effective control of three out of the seven tested phytopathogenic fungi at the highest rate screened. Compounds 17 and 19 h in particular showed activity against the four pathogens screened in artificial media; Pythium dissimile, Alternaria solani, Botryotinia fuckeliana and Gibberella zeae.