A series of novel title compounds 6 a-6 r and 7 a-7 c have been synthesized by Mannich reaction of the new triazole Schiff base intermidiates, substituted piperazine and formaldehyde under mild conditions in excellent yields. The crystal structure of compound 6 i was determined to show a chair conformation of the piperazine ring and an(E)-configuration of the C=N double bond. The bioassay results indicated that most of the newly synthesized compounds exhibited excellent in vitro inhibitory activities and broader spectrum against several plant fungi, and were more effective than the control Triadimefon. Several compounds also displayed favourable in vivo antifungal activities. The relationships between the compound structures and various biological activities were discussed. Furthermore, the CoMFA calculation based on the antifungal activity data of compounds 6 against R. cerealis was carried out to establish a 3 D-QSAR model, which revealed that steric and electrostatic fields were two most important factors for contributing the bioactivity of the compounds. The present work will provide significant information for guiding optimization of such new structures to develop novel agrochemicals with higher antifungal activities.
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