Modification of Azo-Aminopyrimidines as Potent Multitarget Inhibitors of Insect Chitinolytic Enzymes OfChi-h and OfHex1

Multitarget inhibitors exhibit significant advantages in reducing the risk of drug resistance, enhancing therapeutic efficacy, and minimizing dosage, outperforming multicomponent combination drugs. On the basis of glycoside hydrolase family 18 (GH18) chitinases and GH20 β-N-acetylhexosaminidase using the same substrate-assisted catalytic mechanism and similar substrate binding modes, a series of novel azo-aminopyrimidine compounds have been designed and synthesized as multitarget inhibitors targeting chitinolytic enzymes OfChi-h and OfHex1. Compounds AAP4 (OfChi-h, K_i = 29.3 nM; OfHex1, K_i = 4.9 μM) and AAP16 (OfChi-h, K_i = 32.4 nM; OfHex1, K_i = 7.2 μM) were identified to be potent multitarget inhibitors of these enzymes, which were predicted to occupy the −1 subsite and engage in H-binding interactions with catalytic residues. AAP4 also displayed significant insecticidal activity against lepidopteran pests Ostrinia furnacalis through leaf dipping and pot experiments. In addition, the safety of AAP4 to corn and the natural enemy Trichogramma ostriniae was comprehensively evaluated. This present work indicates that azo-aminopyrimidines, as multitarget inhibitors against chitinolytic enzymes, can be further developed as safe and efficient pest control and management agents.