Study on Amphipathic Modification and QSAR of Volatile Turpentine Analogues as Value-Added Botanical Fungicides against Crop-Threatening Pathogenic Fungi

In view of potential agro activity of turpentine analogues, many studies have been conducted on the application of this biorenewable and abundant natural resource. Three series analogues of derivatives from volatile turpentine were prepared to study suitable amphipathic properties. The evaluation of fungicidal activity was carried out against three pathogenic microbials. In addition to the overall good effect, it was found that compounds 2-hydroxyethyl carboxylate, 5k, and 2-(2-hydroxyethoxy)­ethyl carboxylate, 5l, demonstrated extreme activity, with IC50 values of 6.013 and 6.610 μg/mL against Setosphaeria turcica, which were close to the control carbendazim. The preliminary structure–activity relationship (SAR) was analyzed, and compounds with appropriate amphipathic features and small steric hindrance displayed more desirable performances. Meanwhile, the quantitative structure–activity relationship (QSAR) model (R 2 = 0.9548, F = 47.82, S 2 = 0.0125) was built and indicated that the most two important structural features were the total hybridization composite of the molecular dipole and molecular volumn. Moreover, the study of SAR and QSAR indicated that the structural modification of the amphipathic group, which can regulate the permeabilization property of the molecules, was beneficial to the fungicidal activity. On the basis of this, a potential alternative approach may have been discovered to ensure food safety.