A new phytotoxic tetrasubstituted chromen-4-one(1) and a new hexasubstituted benzophenone (2), namedrabenchromenone and rabenzophenone, respectively, were isolatedfrom the culturefiltrates ofFimetariella rabenhorstii, an oak-decline-associated fungus in Iran. Rabenchromenone and rabenzo-phenone, isolated together with known moniliphenone (3) andconiochaetone A (4), were characterized as methyl 3-chloro-1,8-dihydroxy-6-methyl-9-oxo-1,9-dihydrocyclopenta[b]chromene-1-carboxylate and methyl 4-chloro-2-(2,6-dihydroxy-4-methylbenzo-yl)-3-hydroxybenzoate, respectively, by spectroscopic methods(primarily nuclear magnetic resonance and high-resolution electro-spray ionization mass spectrometry). TheRabsolute configurationat C-1 of rabenchromenone was determined by quantum chemical calculations and electronic circular dichroism experiments. Allmetabolites (1−4) were tested by leaf puncture on tomato and oak plants. All compounds were active in this assay by causing inboth plants a necrosis diameter in the range of 0.2−0.7 cm. Specifically, rabenzophenone (2) was found to be the most phytotoxiccompound in both plants.
