Aromatic acyl hydrazono dithiocarbonates are generally biologically active compounds and have a high value of application in crop disease control. In this study, twenty-eight novel dialkyl dithiocarbonates were designed and synthesized, and their molecular structures were determined by 1H NMR, 13C NMR and high-resolution mass spectrometry (HRMS). Four compounds were characterized by X-ray single crystal diffraction as representatives. The bioassay results showed that compound 22 (diethyl dithiocarbonate with a 4-pyridyl and oxadiazole group) and 28 (dibenzyl dithiocarbonate with a p-methoxyphenyl and thiadiazole group) exhibited higher antifungal activities against Magnaporthe grisea and Cercospora arachidicola respectively compared to the control compound Chlorothalonil, while compound 21 (dimethyl dithiocarbonate with a 4-pyridyl and oxadiazole group) and 22 displayed comparable antiviral activities against tobacco mosaic virus (TMV) to the control compound Ribavirin. Structure-activity relationship analysis demonstrated that diethyl thioesters or compounds containing a 4-pyridyl group were more likely to exhibit higher inhibition effects on viruses and fungi, while the introduction of an oxadiazole moiety could contribute to the antiviral activity.

To improve the insecticidal activities of avermectin B2a, the functional carbamate fragment was introduced into the C4" position of avermectin B2a, and 21 novel avermectin B2a C4"-carbamate derivatives were designed, synthesized, and their structures were characterized by high-resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR). The insecticidal activity against Plutella xylostella, Mythimna separata, Spodoptera frugiperda, Ostrinia furnacalis and Helicoverpa armigera was tested. The results showed that the insecticidal activities of most compounds against M. separata, S. frugiperda, O. furnacalis and H. armigera were improved to some degrees. Among them, compound Z5 showed excellent insecticidal activity against M. separata and S. frugiperda, with LC50 values of 1.02 and 2.44 mg/L, respectively. Its insecticidal activity is better than that of the control avermectin B1a, and more than 20 times higher than that of avermectin B2a. The structure-activity relationship analysis showed that more lipophilicity of the compound can help to improve the activity of the target compound. Molecular docking studies showed that with the introduction of the functional carbamate fragment into the C4" position of avermectin B2a, π-π interaction was formed between the benzene ring of the carbamate fragment and the aromatic ring in the receptor protein residue, which was believed to contribute the insecticidal activity of the new compounds.