Turning renewable resources into value-added products: Development of rosin-based insecticide candidates

Rosin is extensively distributed and renewable natural resource in China. In continuation of our research on natural product-based insecticidal agents endowed with eco-friendly properties, 37 rosin-based amide derivatives containing thiadiazole group were prepared. Meanwhile, the structures of rosin-based derivatives containing thiadiazole group were characterized by melting point, IR spectroscopy, 1 H NMR, elemental analysis, ESI-MS and X-ray crystallography. In addition, the insecticidal activities of rosin-based amide derivatives containing thiadiazole group (3a–w and 7a–n) against Mythimna separata and Plutella xylostella were investigated. Compounds 3p–r, 7f and 7n (with LC 50 values of 0.222, 0.222, 0.224, 0.223 and 0.214 μg/mL) displayed outstanding insecticidal activity in comparison with flunbendiamide (a commercial insecticide, with LC 50 value of 0.222 μg/mL). The optimal conformers and best multilinear regression analysis were performed by Gaussian and CODESSA software package, and five descriptors correlating the molecular structures with their insecticidal activities were selected as follows: HOMO–LUMO, log MV, log P, Total Charge I and Total Charge II. For this built QSAR model, the correlation coefficient ( R 2 ) was 0.9604, the squared standard error of the estimates ( S 2 ) was 0.0052, and the Fisher significance ratio ( F ) was 103.79. The preliminary SAR and QSAR studies showed that electronic and steric effect of target compounds had an important influence on the larvicidal activity.