Nine new compounds, tris-aromatic furanones (1, 2, 3a, 3b, and 4) and related bis-aromatic diesters (5a, 5b, 6a, and 6b), are described from the ascidian Synoicum sp. collected off the coast of Chuja-do, Korea. The structures of these compounds, designated as cadiolides E and G-I (1-4) and synoilides A and B (5 and 6), were determined by extensive spectroscopic analyses. The absolute configuration at the asymmetric center of cadiolide G (2) was assigned by ECD analysis. Of these new compounds, cadiolide I and the synoilides possess unprecedented carbon skeletons. Several of these compounds exhibited significant inhibition against diverse bacterial strains as well as moderate inhibition against the enzymes sortase A, isocitrate lyase, and Na(+)/K(+)-ATPase.

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Salternamides A-D (1-4), the first secondary metabolites discovered from saltern-derived actinomycetes, were isolated from a halophilic Streptomyces strain isolated from a saltern on Shinui Island in the Republic of Korea. The planar structures of the salternamides, which are new members of the manumycin family, were elucidated by a combination of spectroscopic analyses. The absolute configurations of the salternamides were determined by chemical and spectroscopic methods, including the modified Mosher's method, J-based configuration analysis, and circular dichroism spectroscopy. Salternamide A (1), which is the first chlorinated compound in the manumycin family, exhibited potent cytotoxicity against a human colon cancer cell line (HCT116) and a gastric cancer cell line (SNU638) with submicromolar IC50 values. Salternamides A and D were also determined to be weak Na(+)/K(+) ATPase inhibitors.