Isolation of thuridillins D-F, diterpene metabolites from the Australian sacoglossan mollusk Thuridilla splendens; relative configuration of the epoxylactone ring.

This first chemical study of the sacoglossan mollusk Thuridilla splendens from Mooloolaba, South East Queensland, has resulted in the isolation of three new metabolites, thuridillins D-F (1-3), and one known metabolite, thuridillin A (4). Thuridillin D (1) was isolated by conventional flash chromatography on silica gel, while a mixture of thuridillins E (2) and F (3) was obtained by PTLC on AgNO(3)-impregnated silica gel. Thuridillins D-F were determined to be structurally related to thuridillin B (5); 1 possessed a hydroxy group at C-11, and 2 and 3 were Δ(10,11)- and Δ(11,12)-isomers, respectively. HSQC-HECADE NMR data, together with conformational analysis, NOESY experiments, and (1)H-(1)H coupling studies enabled assignment of the individual relative configurations of the epoxylactone, the 2,5-diacetoxy-2,5-dihydrofuran, and cyclohexyl moieties within thuridillin D (1).

Daphnane- and tigliane-type diterpenoid esters and orthoesters from Pimelea elongata.

Investigation of Pimelea elongata ("Lakebed Pimelea") afforded 18 tigliane- and daphnane-type diterpenes (1-18). Eight of these were new compounds: four (1-3, 5) tigliane esters and four (7, 8, 10, 11) daphnane orthoesters. The 10 known compounds were 12-O-decanoylphorbol-13-acetate (4), P. simplex subtoxin B (6), wikstroelide E (9), pimelotides A and B (12, 13), gnidiglaucin (14), simplexin (15), huratoxin (16), kirkinine D (17), and 12-ß-acetoxyhuratoxin (18). The structures and relative configurations of the new compounds were determined by 1D and 2D NMR spectroscopic studies in combination with MS analyses.

Pimelotides A and B, diterpenoid ketal-lactone orthoesters with an unprecedented skeleton from Pimelea elongata.

A detailed investigation of the minor phytochemical components of Pimelea elongata foliage led to the discovery of two new diterpenoid daphnane ketal-lactone orthoesters with an unprecedented skeleton, pimelotides A (1) and B (2). Their structures and relative configurations were elucidated by NMR spectroscopy.

Crotalaria medicaginea associated with horse deaths in northern Australia: new pyrrolizidine alkaloids.

Crotalaria medicaginea has been implicated in horse poisoning in grazing regions of central-west Queensland, which resulted in the deaths of more than 35 horses from hepatotoxicosis in 2010. Liver pathology was suggestive of pyrrolizidine alkaloidosis, and we report here the isolation of two previously uncharacterized pyrrolizidine alkaloids from C. medicaginea plant specimens collected from pastures where the horses died. The first alkaloid was shown by mass spectometric and NMR analyses to be 1ß,2ß-epoxy-7ß-hydroxy-1α-methoxymethyl-8α-pyrrolizidine, which, like other alkaloids previously isolated from C. medicaginea, lacks the requisite functionality for hepatotoxcity. The second alkaloid isolated in this investigation was a new macrocyclic diester of otonecine, which we have named cromedine. The (1)H and (13)C NMR spectra of cromedine were fully assigned by 2D NMR techniques and allowed the constitution of the macrocyclic diester to be assigned unambiguously. C. medicaginea specimens implicated in this investigation do not belong to any of the three recognized Australian varieties (C. medicaginea var. neglecta, C. medicaginea var. medicaginea, and C. medicaginea var. linearis) and appear to be a local variant or form, referred to here as C. medicaginea (chemotype cromedine).

Chemistry of Glossodoris nudibranchs: specific occurrence of 12-keto scalaranes.

With the aim of establishing whether the oxidation of the tricyclic carbon skeleton of scalaradial (1) is specific to Glossodoris mollusks, the chemical investigation of specimens of Glossodoris pallida from two distinct geographical areas (China and Guam) and of Glossodoris vespa and Glossodoris averni from Eastern Australia was performed. 12-Deacetoxy-12-oxo-scalaradial (4), recently reported from another Glossodoris nudibranch, was the main metabolite of G. pallida from China, G. vespa, and G. averni. A series of scalarane compounds 3 and 5-11, including the unprecedented 12,16-deacetoxy-12-oxo-scalarafuran 5, was isolated from the mollusks. Interestingly, a population of G. pallida from Guam displayed a different scalarane pattern that was characterized by scalaradial (1), deacetyl scalaradial (2), and deoxoscalarin (3), thus confirming previous reports. The specific occurrence of 12-keto-derivatives in some nudibranchs of the genus Glossodoris is discussed.

Mooloolabenes A-E, norsesterterpenes from the Australian sponge Hyattella intestinalis.

Five new norsesterterpenes, mooloolabenes A-E (1-5), and the new sesterterpene mooloolaldehyde (6), related to the scalarane family of compounds, were isolated from an acetone extract of the Australian sponge Hyattella intestinalis. Structural elucidation, including relative stereochemical assignment, was based on spectroscopic analysis. All compounds tested showed cytotoxic activity against the P388 cell line.

Spongian diterpenes from Australian Nudibranchs: an anatomically guided chemical study of Glossodoris atromarginata.

An Australian population of the nudibranch mollusk Glossodoris atromarginata has been found to contain furanoditerpenes of the spongian series. Spongia-13(16),14-dien-3-one (1) and 3alpha-acetoxy-19-hydroxyspongia-13(16),14-dien-2-one [corrected] (2) were isolated for the first time from a natural source, along with a series of known diterpenes (3-7). Anatomical dissection of the animals revealed the relative distribution and chemical variation of secondary metabolites. Structural studies have provided a basis for chemical comparisons between populations from different geographic locations.