Isolation of C11 cyclopentenones from two didemnid species, Lissoclinum sp. and Diplosoma sp.

A series of new C(11) cyclopentenones 1-7 was isolated, together with four known metabolites 9/10, 12 and 13, from the extract of the didemnid ascidian Lissoclinum sp. The other didemnid ascidian Diplosoma sp. contained didemnenones 1, 2 and 5, and five known metabolites 8-12.

Cytotoxic metabolites from the Okinawan ascidian Diplosoma virens.

The unstable isomeric compounds 5-hydroxy-7-prop-2-en-(E)-ylidene-7,7adihydro-2H-cyclopenta[b]pyran-6-one (1) and 5-hydroxy-7-prop-2-en-(Z)-ylidene-7,7adihydro-2H-cyclopenta[b]pyran-6-one (2), previously described as antimicrobial metabolites from the sponge Ulosa sp., were isolated and identified as major components of the ascidian Diplosoma virens. In this paper, full spectral data for 2 and complete 13CNMR data for 1, based on 2D NMR measurements, are provided for the first time.