Polypropionates from the South African Marine Mollusk <i>Siphonaria oculus</i>

Three new polypropionate metabolites, 6<i>Z</i>,8<i>E</i>-Δ⁸-siphonarienfuranone (<b>1</b>), 6<i>E</i>,8<i>E</i>-Δ⁸-siphonarienfuranone (<b>2</b>), and 6<i>E</i>,8<i>E</i>-3-hydroxy-4,6,8,10,12-pentamethylpentadeca-6,8-dien-5-one (<b>3</b>), and the known polypropionate siphonarienfuranone (<b>4</b>) were isolated from the intertidal South African marine mollusk <i>Siphonaria oculus</i>. Evidence is presented to suggest that <b>1</b>, <b>2</b>, and <b>4</b> may cyclize from an acylic precursor on chromatographic workup of the acetone extract of this mollusk

Antimicrobial Rubrolides from a South African Species of <i>Synoicum</i> Tunicate

The CH₂Cl₂–MeOH extract of a South African tunicate described as the new <i>Synoicum globosum</i> Parker-Nance sp. nov. (Ascidiacea, Aplousobranchia) was subjected to ¹H NMR-guided fractionation. This resulted in the identification of new 3″-bromorubrolide F (<b>1</b>), 3′-bromorubrolide E (<b>2</b>), 3′-bromorubrolide F (<b>3</b>), and 3′,3″-dibromorubrolide E (<b>4</b>) and reisolation of known rubrolides E (<b>5</b>) and F (<b>6</b>), based on NMR spectroscopic and mass spectrometric data. Biological testing of both new and known members of this reported antimicrobial family of halogenated, aryl-substituted furanones indicated moderate antibacterial properties for 3′-bromorubrolide E (<b>2</b>), 3′,3″-dibromorubrolide E (<b>4</b>), and rubrolide F (<b>6</b>) against methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) and <i>S. epidermidis</i>

Mandelalides A–D, Cytotoxic Macrolides from a New <i>Lissoclinum</i> Species of South African Tunicate

Mandelalides A–D are variously glycosylated, unusual polyketide macrolides isolated from a new species of <i>Lissoclinum</i> ascidian collected from South Africa, Algoa Bay near Port Elizabeth and the surrounding Nelson Mandela Metropole. Their planar structures were elucidated on submilligram samples by comprehensive analysis of 1D and 2D NMR data, supported by mass spectrometry. The assignment of relative configuration was accomplished by consideration of homonuclear and heteronuclear coupling constants in tandem with ROESY data. The absolute configuration was assigned for mandelalide A after chiral GC-MS analysis of the hydrolyzed monosaccharide (2-<i>O</i>-methyl-α-l-rhamnose) and consideration of ROESY correlations between the monosaccharide and aglycone in the intact natural product. The resultant absolute configuration of the mandelalide A macrolide was extrapolated to propose the absolute configurations of mandelalides B–D. Remarkably, mandelalide B contained the C-4′ epimeric 2-<i>O</i>-methyl-6-dehydro-α-l-talose. Mandelalides A and B showed potent cytotoxicity to human NCI-H460 lung cancer cells (IC₅₀, 12 and 44 nM, respectively) and mouse Neuro-2A neuroblastoma cells (IC₅₀, 29 and 84 nM, respectively)