Novel 6a,12b-Dihydro-6<i>H</i>,7<i>H</i>-chromeno[3,4-c] chromen-6-ones: Synthesis, Structure and Antifungal Activity

A new series of coumarin derivatives, 7-hydroxy-7-(trifluoromethyl)-6a,12b-dihydro-6H,7H-chromeno[3,4-c]chromen-6-ones 3a&#8722;p, were synthesized via Michael addition, transesterification and nucleophilic addition from the reaction of 3-trifluoroacetyl coumarins and phenols in the presence of an organic base. The products were characterized by infrared spectroscopy (IR), hydrogen nuclear magnetic resonance spectroscopy (1H-NMR), carbon nuclear magnetic resonance spectroscopy (13C-NMR) and high-resolution mass spectrometer (HRMS). Single crystal X-ray analysis of compounds 3a and 3n clearly confirmed their assigned chemical structures and their twisted conformations. Compound 3a crystallized in the orthorhombic system, Pbca, in which a = 8.6244(2) &#197;, b = 17.4245(4) &#197;, c = 22.5188(6) &#197;, &#945; = 90&#176;, &#946; = 90&#176;, &#947; = 90&#176;, v = 3384.02(14) &#197;3, and z = 8. In addition, the mycelial growth rate method was used to examine the in vitro antifungal activities of the title compounds 3a&#8722;p against Fusarium graminearum and Fusarium monitiforme at 500 &#181;g/mL. The results showed that compound 3l exhibited significant anti-Fusarium monitiforme activity with inhibitory index of 84.6%