Synthesis and Structure–Activity Relationship Studies of Nicot­lactone Analogues as Anti-TMV Agents

The synthesis of the originally proposed structure of (±)-nicotlactone A, a potent antiviral lignan with three continuous chiral centers, is reported in 5 steps from methyl acrylate. The key steps of the synthesis included an In-catalyzed regioselective allylation and a Mn-catalyzed Mukaiyama hydration reaction. Our synthetic strategy also enabled us to get the other three epimers and investigate the structure–activity relationship. The NMR data of the synthesized compounds do not match that of the isolated sample, indicating that the structure of nicotlactone A remains to be reassigned. All the synthetic target compounds were evaluated for their anti-tobacco mosaic virus (anti-TMV) activity. Bioassay results indicated that (±)-8-demethylnicotlactone A displayed similar anti-TMV activity to the commercial agent ningnanmycin, thus being a promising candidate or lead compound for developing novel antiviral agents in crop protection.