Hydrated Rubrolides from the New Zealand Tunicate Synoicum kuranui.

LCMS analysis of an extract of the New Zealand tunicate Synoicum kuranui showed evidence for numerous new rubrolides. Following a mass spectrometry-guided isolation procedure, new hydrated rubrolides V and W (5 and 6), along with previously reported rubrolide G (3), were isolated and characterized using MS and NMR. The anti-bacterial and cell cytotoxic activity of the compounds were compared to the potent anti-MRSA compound rubrolide A; hydration across the C-5/C-6 bond was shown to abrogate antibacterial activity.

Targeted Isolation of Rubrolides from the New Zealand Marine Tunicate Synoicum kuranui.

Global natural products social (GNPS) molecular networking is a useful tool to categorize chemical space within samples and streamline the discovery of new natural products. Here, we demonstrate its use in chemically profiling the extract of the marine tunicate Synoicum kuranui, comprised of many previously reported rubrolides, for new chemical entities. Within the rubrolide cluster, two masses that did not correspond to previously reported congeners were detected, and, following MS-guided fractionation, led to the isolation of new methylated rubrolides T (3) and (Z/E)-U (4). Both compounds showed strong growth inhibitory activity against the Gram-positive bacteria Bacillus subtilis, with minimum inhibitory concentration (MIC) values of 0.41 and 0.91 µM, respectively.

A multiproducer microbiome generates chemical diversity in the marine sponge Mycale hentscheli.

Bacterial specialized metabolites are increasingly recognized as important factors in animal-microbiome interactions: for example, by providing the host with chemical defenses. Even in chemically rich animals, such compounds have been found to originate from individual members of more diverse microbiomes. Here, we identified a remarkable case of a moderately complex microbiome in the sponge host Mycale hentscheli in which multiple symbionts jointly generate chemical diversity. In addition to bacterial pathways for three distinct polyketide families comprising microtubule-inhibiting peloruside drug candidates, mycalamide-type contact poisons, and the eukaryotic translation-inhibiting pateamines, we identified extensive biosynthetic potential distributed among a broad phylogenetic range of bacteria. Biochemical data on one of the orphan pathways suggest a previously unknown member of the rare polytheonamide-type cytotoxin family as its product. Other than supporting a scenario of cooperative symbiosis based on bacterial metabolites, the data provide a rationale for the chemical variability of M. hentscheli and could pave the way toward biotechnological peloruside production. Most bacterial lineages in the compositionally unusual sponge microbiome were not known to synthesize bioactive metabolites, supporting the concept that microbial dark matter harbors diverse producer taxa with as yet unrecognized drug discovery potential.

Lamellarin Sulfates from the Pacific Tunicate Didemnum ternerratum.

Six new lamellarin sulfates (1-6) were isolated from the methanolic extract of the Pacific tunicate Didemnum ternerratum, collected from the Kingdom of Tonga. Mass spectrometric molecular networking through the GNPS platform was used to target the isolation of 1-6. Planar structures were elucidated through a combination of NMR and MS experiments. Through comparison of experimental and calculated ECD spectra, the absolute configurations of atropisomers 2-5 were determined, with their energetic barriers to racemization also determined computationally. The cytotoxicity of the compounds was tested against the human colon carcinoma cell line HCT-116, where lamellarin D-8-sulfate (5) exhibited moderate activity with an IC50 of 9.7 µM.

An Acetylenic Lipid from the New Zealand Ascidian Pseudodistoma cereum: Exemplification of an Improved Workflow for Determination of Absolute Configuration of Long-Chain 2-Amino-3-alkanols.

An acetylenic 2-amino-3-alcohol, distaminolyne B (2), isolated from the New Zealand ascidian Pseudodistoma cereum, is reported. The isolation and structure elucidation of 2 and assignment of 2S,3S absolute configuration (AC) using the exciton coupled circular dichroism technique are described. Using a methodologically facile workflow, the same AC was also established by analysis of specific rotation, terminal methyl C-1 δC chemical shift, and NH δH and J values of the N,O-diacetate derivative.

Mono- and dinuclear Ni(i) products formed upon bromide abstraction from the Ni(i) ring-expanded NHC complex [Ni(6-Mes)(PPh3)Br].

Bromide abstraction from the three-coordinate Ni(i) ring-expanded N-heterocyclic carbene complex [Ni(6-Mes)(PPh3)Br] (1; 6-Mes = 1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene) with TlPF6 in THF yields the T-shaped cationic solvent complex, [Ni(6-Mes)(PPh3)(THF)][PF6] (2), whereas treatment with NaBArF4 in Et2O affords the dimeric Ni(i) product, [{Ni(6-Mes)(PPh3)}2(µ-Br)][BArF4] (3). Both 2 and 3 act as latent sources of the cation [Ni(6-Mes)(PPh3)]+, which can be trapped by CO to give [Ni(6-Mes)(PPh3)(CO)]+ (5). Addition of [(Et3Si)2(µ-H)][B(C6F5)4] to 1 followed by work up in toluene results in the elimination of phosphine as well as halide to afford a co-crystallised mixture of [Ni(6-Mes)(η2-C6H5Me)][B(C6F5)4] (4), and [6MesHC6H5Me][B(C6F5)4]. Treatment of 1 with sodium salts of more strongly coordinating anions leads to substitution products. Thus, NaBH4 yields the neutral, diamagnetic dimer [{Ni(6-Mes)}2(BH4)2] (6), whereas NaBH3(CN) gives the paramagnetic monomeric cyanotrihydroborate complex [Ni(6-Mes)(PPh3)(NCBH3)] (7). Treatment of 1 with NaOtBu/NHPh2 affords the three-coordinate Ni(i) amido species, [Ni(6-Mes)(PPh3)(NPh2)] (8). The electronic structures of 2, 5, 7 and 8 have been analysed in comparison to that of previously reported 1 using a combination of EPR spectroscopy and density functional theory.

Ruthenium(ii) complexes of hemilabile pincer ligands: synthesis and catalysing the transfer hydrogenation of ketones.

A series of Ru(ii) complexes were synthesised based on a hemilabile pyrazole-N-heterocyclic carbene (NHC)-pyrazole (C3N2H3)CH2(C3N2H2)CH2(C3N2H3) NCN pincer ligand 1. All complexes were fully characterised using single crystal X-ray crystallography and multinuclear NMR spectroscopy. Hemilabile ligands provide flexible coordination modes for the coordinating metal ion which can play a significant effect on the efficiency and mechanism of catalysis by the resulting complex. Here we observed and isolated mono-, bi- and tri-dentate complexes of both Ag(i) and Ru(ii) with 1 in which the resultant coordination mode was controlled by careful reagent selection. The catalytic activity of the Ru(ii) complexes for the transfer hydrogenation reaction of acetophenone with isopropanol was investigated. The unexpected formation of the pentaborate anion, [B5O6(OH)4](-), during the synthesis of complex 6a was found to have an unexpected positive effect by enhancing the catalysis rate. This work provides insights into the roles that different coordination modes, counterions and ligand hemilability play on the catalytic activity in transfer hydrogenations.

Biologically Active Acetylenic Amino Alcohol and N-Hydroxylated 1,2,3,4-Tetrahydro-ß-carboline Constituents of the New Zealand Ascidian Pseudodistoma opacum.

The first occurrence of an acetylenic 1-amino-2-alcohol, distaminolyne A (1), isolated from the New Zealand ascidian Pseudodistoma opacum, is reported. The isolation and structure elucidation of 1 and assignment of absolute configuration using the exciton coupled circular dichroism technique are described. In addition, a new N-9 hydroxy analogue (2) of the known P. opacum metabolite 7-bromohomotrypargine is also reported. Antimicrobial screening identified modest activity of 1 toward Escherichia coli, Staphylococcus aureus, and Mycobacterim tuberculosis, while 2 exhibited a moderate antimalarial activity (IC50 3.82 µM) toward a chloroquine-resistant strain (FcB1) of Plasmodium falciparum.

Non-invasive imaging and cellular tracking of pulmonary emboli by near-infrared fluorescence and positron-emission tomography.

Functional imaging of proteolytic activity is an emerging strategy to quantify disease and response to therapy at the molecular level. We present a new peptide-based imaging probe technology that advances these goals by exploiting enzymatic activity to deposit probes labelled with near-infrared (NIR) fluorophores or radioisotopes in cell membranes of disease-associated proteolysis. This strategy allows for non-invasive detection of protease activity in vivo and ex vivo by tracking deposited probes in tissues. We demonstrate non-invasive detection of thrombin generation in a murine model of pulmonary embolism using our protease-activated peptide probes in microscopic clots within the lungs with NIR fluorescence optical imaging and positron-emission tomography. Thrombin activity is imaged deep in tissue and tracked predominantly to platelets within the lumen of blood vessels. The modular design of our probes allows for facile investigation of other proteases, and their contributions to disease by tailoring the protease activation and cell-binding elements.

Isolation and stereospecific synthesis of janolusimide B from a New Zealand collection of the bryozoan Bugula flabellata.

NMR-directed screening of New Zealand marine organisms has led to the isolation of the modified tripeptide janolusimide B from the common invasive bryozoan Bugula flabellata. The structure was established by NMR and MS analysis, degradative hydrolysis and derivatization, and stereoselective fragment synthesis. The bryozoan natural product is an N-methyl analogue of janolusimide, previously reported from the Mediterranean nudibranch Janolus cristatus, a species known to prey upon bryozoa.

Hemilabile and bimetallic coordination in Rh and Ir complexes of NCN pincer ligands.

Two new pincer ligands have been developed that contain a central N-heterocyclic carbene (NHC) moiety linked to two pendant pyrazole groups by either a methylene (NCN(me)) or ethylene (NCN(et)) chain. The coordination of these two ligands to rhodium and iridium resulted in a variety of binding modes. Tridentate coordination of the ligands was observed in the complexes [Rh(NCN(me))(COD)]BPh4 (8), [Ir(NCN(me))(COD)]BPh4 (10), [Rh(NCN(et))(CO)2]BPh4 (13), and [Ir(NCN(me))(CO)2]BPh4 (14), and monodentate NHC coordination was observed for [Ir(NCN(me))2(COD)]BPh4 (11) and [Ir(NCN(et))2(COD)]BPh4 (12). Both tridentate and bidentate coordination modes were characterized for [Rh(NCN(et))(COD)]BPh4 (9) in the solution and solid state, respectively, while an unusual bridging mode was observed for the bimetallic complex [Rh(µ-NCN(me))(CO)]2(BPh4)2 (15). The impact of this diverse coordination chemistry on the efficiency of the complexes as catalysts for the addition of NH, OH, and SiH bonds to alkynes was explored.

Age-related susceptibility to Japanese encephalitis virus in domestic ducklings and chicks.

Ardeid birds and pigs are known as major amplifying hosts for Japanese encephalitis virus, and ducklings and chickens have been considered to play at best a minor role in outbreaks because of their low or absent viremia. We hypothesized that viremia of sufficient magnitude would develop in young ducklings (Anas platyrhynchos) and chicks (Gallus gallus) for them to serve as reservoir hosts and thereby contribute to the transmission cycle. Infection was associated with reduced weight gain in both species, and ducklings infected at 10 days of age or less showed overt clinical signs of disease. The mean peak viremia in birds of both species decreased as the age at infection increased from 2 to 42 days, indicating the importance of age of infection on magnitude of viremia in birds from both species, and suggesting that young poultry may be amplifying hosts of importance in disease-endemic regions.

Synthesis, electronic structure, and magnetism of [Ni(6-Mes)2]+: a two-coordinate nickel(I) complex stabilized by bulky N-heterocyclic carbenes.

The two-coordinate cationic Ni(I) bis-N-heterocyclic carbene complex [Ni(6-Mes)2]Br (1) [6-Mes =1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene] has been structurally characterized and displays a highly linear geometry with a C-Ni-C angle of 179.27(13)°. Density functional theory calculations revealed that the five occupied metal-based orbitals are split in an approximate 2:1:2 pattern. Significant magnetic anisotropy results from this orbital degeneracy, leading to single-ion magnet (SIM) behavior.

Three-coordinate nickel(I) complexes stabilised by six-, seven- and eight-membered ring n-heterocyclic carbenes: synthesis, EPR/DFT studies and catalytic activity.

Comproportionation of [Ni(cod)(2)] (cod = cyclooctadiene) and [Ni(PPh(3))(2)X(2)] (X = Br, Cl) in the presence of six-, seven- and eight-membered ring N-aryl-substituted heterocyclic carbenes (NHCs) provides a route to a series of isostructural three-coordinate Ni(I) complexes [Ni(NHC)(PPh(3))X] (X = Br, Cl; NHC = 6-Mes 1, 6-Anis 2, 6-AnisMes 3, 7-o-Tol 4, 8-Mes 5, 8-o-Tol 6, O-8-o-Tol 7). Continuous wave (CW) and pulsed EPR measurements on 1, 4, 5, 6 and 7 reveal that the spin Hamiltonian parameters are particularly sensitive to changes in NHC ring size, N substituents and halide. In combination with DFT calculations, a mixed SOMO of ∣3d z 2〉 and ∣3d x 2-y 2〉 character, which was found to be dependent on the complex geometry, was observed and this was compared to the experimental g values obtained from the EPR spectra. A pronounced (31)P superhyperfine coupling to the PPh(3) group was also identified, consistent with the large spin density on the phosphorus, along with partially resolved bromine couplings. The use of 1, 4, 5 and 6 as pre-catalysts for the Kumada coupling of aryl chlorides and fluorides with ArMgY (Ar = Ph, Mes) showed the highest activity for the smaller ring systems and/or smaller substituents (i.e., 1>4≈6≫5).

Anti-inflammatory and antimalarial meroterpenoids from the New Zealand ascidian Aplidium scabellum.

Bioassay-directed fractionation of an extract of the New Zealand ascidian Aplidium scabellum has afforded the anti-inflammatory secondary metabolite 2-geranyl-6-methoxy-1,4-hydroquinone-4-sulfate (1) and a family of pseudodimeric meroterpenoids scabellones A (2)-D (5). The benzo[c]chromene-7,10-dione scaffold contained within scabellones A-D is particularly rare among natural products. The structures were elucidated by interpretation of NMR data. Scabellone B was also identified as a moderately potent, nontoxic inhibitor of Plasmodium falciparum.

Antimalarial ß-carbolines from the New Zealand ascidian Pseudodistoma opacum.

One tetrahydro-ß-carboline, (-)-7-bromohomotrypargine (1), and three alkylguanidine-substituted ß-carbolines, opacalines A, B, and C (2-4), have been isolated from the New Zealand ascidian Pseudodistoma opacum. The structures of the metabolites were determined by analysis of mass spectrometric and 2D NMR spectroscopic data. Natural products 2 and 3, synthetic debromo analogues 8 and 9, and intermediate 16 exhibited moderate antimalarial activity toward a chloroquine-resistant strain of Plasmodium falciparum, with an IC50 range of 2.5-14 µM. The biosynthesis of 1-4 is proposed to proceed via a Pictet-Spengler condensation of 6-bromotryptamine and the α-keto acid transamination product of either arginine or homoarginine. Cell separation and 1H NMR analysis of P. opacum identified tetrahydro-ß-carboline 1 to be principally located in the zooids, while fully aromatized analogues 2-4 were localized to the test.

Formation and reactivity of the cyclometallated N-heterocyclic carbene complexes [Ru(NHC)'(dppe)(CO)H].

Thermolysis of [Ru(PPh(3))(dppe)(CO)HCl] (dppe = 1,2-bis(diphenylphosphino)ethane) with the N-heterocyclic carbenes I(i)Pr(2)Me(2) (1,3-diisopropyl-4,5-dimethyl-imidazol-2-ylidene), IEt(2)Me(2) (1,3-diethyl-4,5-dimethyl-imidazol-2-ylidene) or ICy (1,3-dicyclohexylimidazol-2-ylidene) gave the cyclometallated carbene complexes [Ru(NHC)'(dppe)(CO)H] (NHC = I(i)Pr(2)Me(2), 4; IEt(2)Me(2), 5; ICy, 6). Dissolution of 4 in CH(2)Cl(2) or CHCl(3) gave the trans-Cl-Ru-P complex [Ru(I(i)Pr(2)Me(2))'(dppe)(CO)Cl] (7), which converted over hours at room temperature to the trans-Cl-Ru-CO isomer 7'. Chloride abstraction from 7 by NaBPh(4) under an atmosphere of H(2) produced the cationic mono-hydride complex [Ru(I(i)Pr(2)Me(2))(dppe)(CO)H][BPh(4)] (9), which could also be formed by protonating 4 with 1 eq HBF(4)·OEt(2). Treatment of 4 with excess HBF(4)·OEt(2) followed by extraction into MeCN produced the dicationic acetonitrile complex [Ru(I(i)Pr(2)Me(2))(dppe)(CO)(NCMe)(2)][BF(4)](2) (10). The structures of 6, 7, 7' and 10 have been determined by X-ray crystallography.

Proteases as therapeutics.

Proteases are an expanding class of drugs that hold great promise. The U.S. FDA (Food and Drug Administration) has approved 12 protease therapies, and a number of next generation or completely new proteases are in clinical development. Although they are a well-recognized class of targets for inhibitors, proteases themselves have not typically been considered as a drug class despite their application in the clinic over the last several decades; initially as plasma fractions and later as purified products. Although the predominant use of proteases has been in treating cardiovascular disease, they are also emerging as useful agents in the treatment of sepsis, digestive disorders, inflammation, cystic fibrosis, retinal disorders, psoriasis and other diseases. In the present review, we outline the history of proteases as therapeutics, provide an overview of their current clinical application, and describe several approaches to improve and expand their clinical application. Undoubtedly, our ability to harness proteolysis for disease treatment will increase with our understanding of protease biology and the molecular mechanisms responsible. New technologies for rationally engineering proteases, as well as improved delivery options, will expand greatly the potential applications of these enzymes. The recognition that proteases are, in fact, an established class of safe and efficacious drugs will stimulate investigation of additional therapeutic applications for these enzymes. Proteases therefore have a bright future as a distinct therapeutic class with diverse clinical applications.

Didemnidines A and B, indole spermidine alkaloids from the New Zealand ascidian Didemnum sp.

Two new indole spermidine alkaloids, didemnidines A (1) and B (2), have been isolated from the New Zealand ascidian Didemnum sp. The structures of the metabolites, determined by analysis of 2D NMR spectra and confirmed via synthesis, embody an indole-3-glyoxylamide moiety linked to the N(1) position of spermidine, the latter motif being particularly rare among marine natural products. Didemnidine B and a synthetic precursor exhibited mild in vitro growth inhibition of Plasmodium falciparum with IC(50)'s of 15 and 8.4 µM, respectively.