Curvularin and Dehydrocurvularin as Phytotoxic Constituents from <i>Curvularia intermedia</i> Infecting <i>Pandanus amaryllifolius</i>

Microbes are good sources of biologically active compounds that can be used as pharmaceuticals and agrochemicals. As part of our continuous efforts in search for biopesticides from natural sources, a fungus is isolated from leaves of Pandanus amaryllifolius that shows severe necrosis. This fungus is cultured in potato dextrose agar and identified as Curvularia intermedia. The ethyl acetate extract of the liquid culture medium is phytotoxic. Identification and bioassay of αβ-dehydrocurvularin (1) and curvularin (2) from this fungus are described. Monoacetyldehydrocurvularin (3), and diacetyldehydrocurvularin (4) are synthesized from 1. Phytoxicity rankings in a variety of bioassays are 1 > 2 > 4 > 3.