New cyclic peroxides from the Philippine sponge Plakinastrella sp.

Three new cyclic peroxides 5-7 and a new carboxylic acid ester 8 were isola ted as minor metabolites from the hexane extract of a Plakinastrella specie s from the Philippines. The structures of compounds 5-8 were elucidated by interpretation of spectral data and by chemical interconversion, and the ab solute stereochemistry of peroxide 6 was determined by application of Moshe r's method to a derivative. Although the major compounds in the sponge show ed activity against Candida albicans prior to decomposition, the minor meta bolites 5-8 are essentially inactive.