A series of novel a-aminophosphonates containing 6-fluorobenzothiazole moiety derivatives were synthesized by one-pot reaction under microwave irradiation and their structures were characterized by IR, ¹H, ¹³C, and ³¹P NMR and element analysis data. Antiviral assays showed that some compounds possess good curative and protective activities against tobacco mosaic virus (TMV) in vivo at 500 µg/mL In particular, compounds diethyl [(6-fluorobenzo[d]thiazol-2-ylamino)(phenyl)methyl]phosphonate (4b), diethyl [(6-methoxybenzo[d]thiazol-2-ylamino)(thiophen-2-yl)methyl]phosphonate (4j) and diphenyl [(6-fluorobenzo[d]thiazol-2-ylamino)(4-methoxyphenyl)methyl]phosphonate (4q) exhibited remarkable antiviral activities than Ribavirin against TMV and PVY. Compound diphenyl [(6-fluorobenzo[d]thiazol-2-ylamino)(4-methoxyphenyl)methyl]phosphonate (4q) showed similar curative and protective activity against potato virus Y (PVY) to Dufulin.

Plant immune activators can protect crops from plant virus pathogens by activating intrinsic immune mechanisms in plants and are widely used in agricultural production. In our previous work, we found that curcumin analogs exhibit excellent biological activity against plant viruses, especially protective activity. Inspired by these results, the active substructure of pentadienone and quinazoline were spliced to obtain curcumin analogs as potential exogenously induced resistant molecule. Bioassay results showed that compound A13 exhibited excellent protective activity for tobacco to against Tobacco mosaic virus (TMV) at 500 μg/mL, with a value of 70.4 ± 2.6% compared with control treatments, which was better than that of the plant immune activator chitosan oligosaccharide (49.0 ± 5.9%). The protective activity is due to compound A13 inducing tobacco resistance to TMV, which was related to defense-related enzymes, defense-related genes, and photosynthesis. This was confirmed by the up-regulated expression of proteins that mediate stress responses and oxidative phosphorylation.