Plakortides I-L, four new cyclic peroxides from an undescribed Jamaican sponge Plakortis sp (Homosclerophorida, Plakinidae)

Four new polyketide-derived cyclic peroxides, plakortides I (1), J (2), K ( 3) and L (4), were isolated from an undescribed sponge of the genus Plakort is collected at Discovery Bay, Jamaica. The structures were elucidated by s pectral analysis including the 2D NMR techniques. The relative stereochemis try of the plakortides was established by NOESY NMR experiments. Plakortide 1 (1) represents the first report of a polyketide-derived cyclic peroxide with an alpha,beta -unsarurated ketone moiety in the side chain and exhibit s significant antimalarial activity against the W2 Clone of Plasmodium falc iparum with an IC50 of 570 ng mL(-1) and a selectivity index of > 8.4. (C) 2001 Elsevier Science Ltd. All rights reserved.