Synthesis, Fungicidal Activity, and Sterol 14α-Demethylase Binding Interaction of 2‑Azolyl-3,4-dihydroquinazolines on Penicillium digitatum

A series of new 2-azolyl-3,4-dihydroquinazolines <b>6</b> was synthesized by direct cyclization of imidazole or 1,2,4-triazole with carbodiimides <b>4</b>, which were obtained from aza-Wittig reaction of iminophosphorane <b>3</b> with isocyanate. The preliminary bioassay results demonstrated that most of the 2-imidazolyl-3,4-dihydroquinazolines <b>6a</b>–<b>6i</b> exhibited good to significant fungicidal activity against Penicillium digitatum, whereas 2-triazolyl-3,4-dihydroquinazolines <b>6j</b>–<b>6t</b> exhibited low fungicidal activity. Some of the 2-imidazolyl-3,4-dihydroquinazolines <b>6a</b>–<b>6i</b> also exhibited strong binding interaction with the cytochrome P450-dependent sterol 14α-demethylase (CYP51). For example, compound <b>6e</b> showed the best fungicidal activity against <i>P. digitatum</i> with IC<sub>50</sub> = 4.14 μg/mL and the best CYP51 binding activity with <i>K</i><sub>d</sub> = 0.34 μg/mL, both superior to those of the agricultural fungicide triadimefon.