New peroxylactones from the Jamaican sponge Plakinastrella onkodes, with inhibitory activity against the AIDS opportunistic parasitic infection Toxoplasma gondii

An analysis of the chemical constituents of Plakinastrella onkodes collected in Jamaica yielded three cyclic peroxides, including the known plakortolide (1) and two new analogs of 1. The absolute configuration of plakortolide G ((3R,4R,6R,8S)-3) was determined by ab initio optical rotation computations using a coupled Hartree–Fock (CHF) method implemented in CADPAC. Plakortolide (1) (J. Org. Chem. 1980, 45, 3396) and plakortolide G (3) exhibited potent inhibitory activity against the protozoan Toxoplasma gondii in HFF cells and represent the first marine natural products reported with T. gondii inhibitory activity.