Natural Product Cerbinal and Its Analogues Cyclopenta[c]pyridines: Synthesis and Discovery as Novel Pest Control Agents

Owing to the changing needs of agriculture, the exploration of new pest control agents remains as critical as ever. The analogues 3a–3v of the natural product cerbinal were synthesized from genipin by an efficient and practical method under additive-free conditions. The antiviral and insecticidal effects of cerbinal and these cyclopenta­[c]­pyridines (3a–3v) were evaluated systematically. Most of the synthesized compounds exhibited higher anti-TMV activities than the lead compound cerbinal. Compound 3s (2-(4-methoxyphenyl)) had the most promising inhibitory activities against TMV (inactivation effect 49.0 ± 0.8%, curative effect 41.2 ± 4.3%, and protection effect 51.5 ± 2.7% at 500 μg/mL). Among the synthesized compounds, only 3v (2-(2-chloro-4-(trifluoromethoxy)­phenyl)) reached the activity level of cerbinal against Plutella xylostella. This suggested that the cyclopenta­[c]­pyridines obtained by modifications of cerbinal at position 2 are very significant for the anti-TMV activity, and yet were exceptionally less active for the insecticidal activities.