Novel conjugated 5-alkenyl rhodanine tethered 1,4-benzodioxane derivatives as dual-chitinases inhibitors to hinder the growth of Asian corn borer

OfChtI and OfChi-h are ideal targets for developing agricultural inhibitors against Ostrinia furnacalis. In order to further confirm the importance of conjugated systems in rhodanine derivatives, sixteen novel 1,4-benzodioxane-tethered-rhodanine derivatives were designed and synthesized with or without C=C double bond of 5-alkenyl rhodanine skeleton. Among them, compounds 3a–3h, with preserved 5-alkenyl rhodanine skeleton, all exhibited much better inhibitory activities against both OfChtI and OfChi-h, compared to that of the corresponding reduced compounds 4a–4h without its C=C double bond. The inhibitory mechanism demonstrated that the 5-alkenyl rhodanine conjugated plane was conducive to improving the binding affinity with both two chitinases. Compound 3g was identified as the most potential dual-chitinases inhibitor against OfChtI (K_i = 2.57 μM) and OfChi-h (K_i = 2.03 μM). The bioassay study also indicated that compound 3g displayed the best insecticidal activity against O. furnacalis and distinctive sublethal effect in regulating its growth and development. These 1,4-benzodioxane-tethered-rhodanine derivatives deserved further investigation as novel dual-chitinases inhibitor candidates in the control of O. furnacalis.