Microwave-assisted synthesis and antifungal activity of novel coumarin derivatives: Pyrano[3,2-c]chromene-2,5-diones.

A series of novel fused coumarin analogues pyrano[3,2-c]chromene-2,5-diones have been synthesized through an optimized microwave-assisted protocol. All target compounds were tested and evaluated for their antifungal activity against Botrytis cinerea, Colletotrichum copsica, Alternaria solani, Gibberella zeae and Rhizoctorzia solani. The bioassay results indicated that some of the compounds exhibited potent antifungal activities at concentration less than 50 ppm. For the compounds 5d, 6c and 7b, EC50 values against B. cinerea were as low as 0.141, 0.082 and 0.091 μM, respectively, which represents better antifungal activity than that of the commonly used fungicide Azoxystrobin. Compounds 5d (57%) and 6c (55%) also exhibited more effective control than Azoxystrobin (44%) against Colletotrichum capsica.