Synthesis and Quantitative Structure-Activity Relationship (QSAR) Study of Novel N-Arylsulfonyl-3-acylindole Arylcarbonyl Hydrazone Derivatives as Nematicidal Agents

In continuation of our program aimed at the discovery and development of natural-product-based pesticidal agents, 54 novel N-arylsulfonyl-beta-acylindole arylcarbonyl hydrazone derivatives were prepared, and their structures were well characterized by H-1 NMR, C-13 NMR, HRMS, ESI-MS, and mp. Their nematicidal activity was evaluated against that of the pine wood nematode, Bursaphelenchus xylophilus in vivo. Among all of the derivatives, especially V-12 and V-39 displayed the best promising nematicidal activity with LC50 values of 1.0969 and 1.2632 mg/L, respectively. This suggested that introduction of RI and R-2 together as the electron-withdrawing substituents, R-3 as the methyl group, and R-4 as the phenyl with the electron-donating substituents could be taken into account for further preparation of these kinds of compounds as nematicidal agents. Six selected descriptors are a WHIM descriptor (E1m), two GETAWAY descriptors (R1m+ and R3m+), a Burden eigenvalues descriptor (BEHm8), and two edge-adjacency index descriptors (EEig05x and EEig13d). Quantitative structure-activity relationship (QSAR) studies demonstrated that the structural factors, such as molecular mass (a negative correlation with the bioactivity) and molecular polarity (a positive correlation with bioactivity), are likely to govern the nematicidal activities of these compounds. For this model, the correlation coefficient (R-training set(2)), the leave-one-out cross-validation correlation coefficient (Q(LOO)(2)), and the 7-fold cross-validation correlation coefficient (Q(7-fold)(2)) were 0.791, 0.701, and 0.715, respectively. The external cross-validation correlation coefficient (Q(ext)(2)) and the root-mean-square error for the test set (RMSEtest set) were 0.774 and 3.412, respectively. This study will pave the way for future design, structural modification, and development of indole derivatives as nematicidal agents.