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 1H 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, 18h, 18o, 19h, 19i and 19l all showed effective control of three out of the seven tested phytopathogenic fungi at the highest rate screened. Compounds 17 and 19h in particular showed activity against the four pathogens screened in artificial media; Pythium dissimile, Alternaria solani, Botryotinia fuckeliana and Gibberella zeae.

Graphical abstractA simple and efficient synthetic protocol for 5-(3-indolyl)-oxazoles has been developed. By this new protocol, a series of novel pimprinine analogues were synthesized and screened for the fungicidal activity.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A simple and efficient synthesis of 5-(3-indolyl)-oxazoles has been developed. ► Thirty six novel analogues of natural product pimprinine were synthesized and screened. ► The structure–activity relationships of pimprinine analogues were summarized for the first time.