Synthesis, characterization, and reactivity of (π-allyl)palladium(II) wrap-around complexes with 1,3-dienes

Synthesis of a series of cationic “wrap-around” complexes, η³-, η²- (CH₂-CH-CHR-CH₂-CH₂-CHCHX) Pd(II)L⁺ (R = H, CH₃; X = H, Cl, CO₂Me; L = PPh₃, P(C₄H₄N)₃), is described. These chelate complexes were prepared by exposure of π-allyl chloride dimers, (η³-(CH₂-CX-CH₂)PdCl)₂, to either 1,3-butadiene or isoprene to yield π-allyl chloride dimers of the type (η³-CH₂CHCRCH₂CH₂CH = CH(X)PdCl)₂ which result from insertion of the diene into each π-allyl unit. Abstraction of chloride with either AgSbF₆ or NaB(Ar_F)₄ in the presence of L gives the cationic wrap-around complexes in high yields. Single crystal X-ray diffraction studies of 8a (R = -CH₃, X = -Cl, L = PPh₃) and 9a (R = -H, X = -Cl, L = PPh₃) show that Pd(II) adopts essentially a square planar geometry and the chelate arm occupies a syn orientation with respect to the allyl unit. Exposure of these wrap-around complexes to nitriles of differing basicities displaces the chelated alkene to varying extents and allows assessment of the relative strengths of chelation as a function of substituents, X and R. Initial rapid displacement of the chelated alkene yields a syn-π-allyl isomer which equilibrates with the anti-π-allyl isomer which cannot close to form a chelate. Treatment of 8b with 1,3-butadiene gives not polybutadiene but 2-chloro-4-methyl-1,E-4,6-heptatriene and 2-chloro-4-methyl-1,Z-4,6-heptatriene. Formation of these trienes is first-order in butadiene. This reaction serves as a model for chain-transfer in the polymerization of butadiene.     

Redescription ofApogon (Ostorhinchus) fleurieu (Lacepède, 1802) with notes on its synonymy

The speciesOstorhinchus fleurieu Lacepède, 1802 is recognized as a senior synonym ofApogon aureus (Lacepède, 1802) on the basis of diagnostic colour features of Lacepède’s illustration of the species (after Commerson). The species is redescribed and a neotype designated. The synonymy of the species is discussed in the light of the history of Commerson’s and Lacepède’s work.Nectamia is replaced byOstorhinchus as a subgenus ofApogon.     

Interaction of ruthenium(III) chloride with bis(3,5-dimethylpyrazol-1-yl)methane oxyanions, potential κ-N,N,O scorpionates

When RuCl₃ was set to react with both bis(3,5-dimethylpyrazol-1-yl)acetate (bdmpza) and bis(3,5-dimethylpyrazol-1-yl)methane sulfonate (bdmpzsa) new ruthenium(II) complexes were obtained. The reduction of ruthenium(III) was studied by the NMR Evans method and spectrophotometrically, for 1:1 (Ru:L) molar ratios. Using the Evans method pseudo first-order constants of 2.5 × 10⁻³ s⁻¹ (bdmpzsa) and 3.9 × 10⁻³ s⁻¹ (bdmpza) were obtained in DMSO-d₆ (2% t-butanol) solutions. Spectrophotometrically the corresponding constants were also calculated: 1.1 × 10⁻³ s⁻¹ for bdmpzsa, and 1.6 × 10⁻³ s⁻¹, for bdmpza. Both ligands behave as κ³-N,N,O scorpionates but with a weak oxyanionic coordination to the metal, susceptible to be substituted with NEt₃ for a 1:1 molar ratio.     

Protective Group-Free Syntheses of (±)-Frontalin, (±)-endo-Brevicomin, (±)-exo-Brevicomin,and (±)-3,4-Dehydro-exo-brevicomin: Racemic Pheromones with a 6,8-Dioxabicyclo[3.2.1]octane Ring

Protective group-free syntheses of four racemic pheromones with a 6,8-dioxabicyclo[3.2.1]octane ring were achieved in five or six steps from commercially available (±)-3-butyn-2-ol (6) and 2-alkenyl halides or 2-alken-1-ol by employing Lewis acid-catalyzed acetalization of δ, ε-epoxy ketones as the key reaction. (±)-Frontalin (1) was prepared in a 25% overall yield in five steps from methallyl chloride (5a), (±)-endo-brevicomin (2) was prepared in a 23% overall yield in five steps from (E)-2-pentenyl bromide (5b), and (±)-exo-brevicomin (3) and (±)-3,4-dehydro-exo-brevicomin (4) were both prepared in a 4% overall yield in six steps based on (Z)-2-penten-1-ol (12).     

Protective group-free syntheses of (±)-frontalin, (±)-endo-brevicomin, (±)-exo-brevicomin, and (±)-3,4-dehydro-exo-brevicomin: racemic pheromones with a 6,8-dioxabicyclo[3.2.1]octane ring

Protective group-free syntheses of four racemic pheromones with a 6,8-dioxabicyclo[3.2.1]octane ring were achieved in five or six steps from commercially available (±)-3-butyn-2-ol (6) and 2-alkenyl halides or 2-alken-1-ol by employing Lewis acid-catalyzed acetalization of δ, ε-epoxy ketones as the key reaction. (±)-Frontalin (1) was prepared in a 25% overall yield in five steps from methallyl chloride (5a), (±)-endo-brevicomin (2) was prepared in a 23% overall yield in five steps from (E)-2-pentenyl bromide (5b), and (±)-exo-brevicomin (3) and (±)-3,4-dehydro-exo-brevicomin (4) were both prepared in a 4% overall yield in six steps based on (Z)-2-penten-1-ol (12).     

New record of Machaeriobia machaerii (Kieffer, 1913) (Diptera,Cecidomyiidae) in Brazil and association with host–plant species

The geographical distribution of Machaeriobia machaerii (Kieffer, 1913) (Diptera, Cecidomyiidae), previously known only from Tubarão, Santa Catarina State, Brazil is extended to São Paulo State, Brazil. Illustrations of diagnostic characters of the male, pupa, and larva are provided, and the association with the species of host plant, Machaerium hirtum (Vell.) Stellfeld (Fabaceae) is established.     

BmSE, a SINE family with 3′ ends of (ATTT) repeats in domesticated silkworm (Bombyx mori)

Short interspersed elements (SINEs), which are mainly composed of Bm1, are abundant in the domesticated silkworm. A 294 bp novel SINE family, designated as BmSE, was identified by mining the database of the complete Bombyx mori genome. A representational BmSE element is flanked by an 11 bp target site duplication sequence posterior poly (A) at the 3′ end and has the sequence motifs of an internal promoter of RNA polymerase III, which are similar to that of Bm1. The repetitive elements of BmSE are ...     

Synthesis, characterization and cytotoxic activity of palladium (II) dithiocarbamate complexes with α,ω-diamines

The polymeric [PdCl(dithiocarbamate)]_n complexes, in which the ligand ion is dimethyldithiocarbamate (DMDT), pyrrolidine dithiocarbamate (PyDT, (CH₂)₄NCS₂⁻) and sarcosine ethyl ester dithiocarbamate (ESDT, EtO₂CCH₂N(CH₃)CS₂⁻), have been reacted with chelating diamines, like ethylenediamine (en) or 1,3-diaminopropane (dap) and long chain diamines, like 1,4-diaminobutane (dab) or 1,7-diaminoheptane (dah). The reaction products depend on either diamine chain length or molar ratio. By operating at PdCl(dithiocarbamate)/diamine molar ratio 1:1 chelating diamines yielded the ionic [Pd(dithiocarbamate)(diamine)]Cl species (diamine = en or dap), whereas with long chain diamines species of the type [Pd(dithiocarbamate)(diamine)]_nCl_n (diamine = dab or dah) were obtained, in which each Pd(dithiocarbamate)⁺ unit binds to the NH₂ group of two different molecules, in a network of bridging diamines. At molar ratio 1:0.5, the long chain diamines yielded the binuclear [Pd₂Cl₂(dithiocarbamate)₂(diamine)] complexes (diamine = dab or dah), whereas exchange reactions take place generally in the presence of en or dap. The reaction trend is described on the basis of IR and proton NMR spectra. The new dithiocarbamate complexes were preliminarily tested for their cytotoxicity on human cancer cells.     

Interactions ofMonoporeia affinis (Lindström) (Amphipoda) with sedentary Chironomidae

Interannual population oscillations ofMonoporeia affinis and sedentary chironomids are negatively correlated in Lake Mälaren. Sedentary chironomid abundance regressed againstM. affinis density was highly significant at a lag response of one year (adj. R²=0.54, P=0.0001). The inverse correlation between Tanytarsini (Micropsectra sp. andTanytarsus sp.) andM. affinis densities supports a recruitment limitation hypothesis,viz. that the growth or survival of early instar chironomids is low at high amphipod densities. Microcosm studies showed density-dependent effects on the growth and survival of second instarCh. riparius larvae across an amphipod density gradient. No significant effects were found on growth or survival of third instars. These findings support the chironomid recruitment limitation hypothesis. Amphipod predation on early instar chironomid larvae is suggested as a population controlling mechanism.     

Tissue Selenium in Pigs with Dietetic Microangiopathy (MAP, “Mulberry Heart”)

Mean selenium contents of liver, heart muscle and skeletal muscle of pigs with dietetic microangiopathy (MAP), but without waxy muscle degeneration (MD) and hepatosis diaetetica (HD), were 1113, 850 and 265 ng/g d.s., respectively. These values were not lower than corresponding values of control pigs without MAP, MD and HD.     

Nanoparticle (CdS) interaction with host (Sesamum indicum L.) – its localization,transportation, stress induction and genotoxicity

The present study highlights the nanoimpact of cadmium sulfide quantum dots on a plant system (Sesamum indicum L.) encompassing uptake of nanoparticles (NPs), subsequent translocation following root to leaf transportation pathway using both water- and food-conducting elements and deposition in nucleus and cytoplasm with no preferential subcellular localization. Nanocrystal agglomeration, mucilaginous sheathing and vesicularization studied are the host toxicity minimization attempt. Cellular stress due to NPs is recorded in the form of elevated production of hydrogen peroxide and malondialdehyde. However, non-synchronous activation of ascorbate peroxidase-monodehydroascorbate reductase-glutathione reductase-glutathione S-transferase enzyme system contributes to failure of anti-oxidative response and persistence of stress environment. Flow cytometric assessment reveals changes in cellular metabolic event along with blockage of cell division at G₁ phase and enhances apoptotic cell death. Nuclear internalization along with oxidative burst results in generation of DNA double-strand break which can be the focal point of genome alteration and subsequent gene mutation.     

Total synthesis of (±)-elegansidiol, (±)-farnesiferol B,and (±)-farnesiferol D

The racemic total synthesis of elegansidiol, farnesiferol B, and farnesiferol D has been obtained following a Diels–Alder approach. Gillman addition, cross metathesis reaction are the other key steps involved in the target synthesis.     

Pt(II) complexes with (N,N′) or (C,N,E)− (E = N,S) ligands: Cytotoxic studies,effect on DNA tertiary structure and structure–activity relationships

The cytotoxic activity of two series of platinum(II) complexes containing the polyfunctional imines R¹–CHN–R² [R¹ = phenyl or ferrocenyl unit and R² = (CH₂)_n–CH₂–NMe₂ where n = 1 or 2) (1 and 2) or C₆H₄-2-SMe (3)] acting as a bidentate (N,N′) (4–7) or terdentate [C(phenyl or ferrocenyl),N,N′]^? (8–10) or [C(ferrocenyl),N,S]^? ligand (11) in front of A549 lung, MDA-MB231 breast and HCT116 colon human adenocarcinoma cell lines is reported. The results reveal that most of the platinum(II) complexes are active against the three assayed lines and compounds 6, 7 and the platinacycles 10 and 11 exhibit a remarkable antiproliferative activity, even greater than cisplatin itself, in the cisplatin resistant HCT116 human cancer cell line. Electrophoretic DNA migration studies showed that most of them modify the DNA tertiary structure in a similar way as the reference cisplatin. Solution studies of a selection of the most relevant complexes have also been performed in order to test: (a) their stability in the aqueous biological medium and/or the formation of biologically active species and (b) their proclivity to react with 9-methylguanine (9-MeG), as a model nucleobase. Computational studies at DFT level have also been performed in order to explain the different solution behaviour of the complexes and their proclivity to react with the nucleobase.     

The genus Aspidimerus Mulsant, 1850 (Coleoptera,Coccinellidae) from China,with descriptions of?two?new species

Chinese members of the genus Aspidimerus Mulsant, 1850 are reviewed. Ten species are recognized, including two new species: A. zhenkangicus Huo & Ren, sp. n. and A. menglensis Huo & Ren, sp. n. A. kabakovi Hoàng is recorded from China for the first time. A. blandus (Mader, 1954) is recognized as synonymous with A. ruficrus Gorham, 1895 (syn. n.). Aspidimerus rectangulatus Kuznetsov & Pang, 1991 and A. serratus Kuznetsov & Pang, 1991 are transferred to the genus Pseudaspidimerus Kapur, 1948 (comb. n.). All species from China are described and illustrated. Distribution maps of the Chinese species, a key and a catalogue of all known Aspidimerus are provided.     

N,N-Bis-(8-hydroxyquinoline-5-yl methyl)-benzyl substituted amines (HQNBA): peroxisome proliferator-activated receptor (PPAR-γ) agonists with neuroprotective properties

We report on the neuroprotective effects of N,N-bis-(8-hydroxyquinoline-5-yl methyl)-benzyl substituted amines (HQNBA) in a model of oxidative stress-induced nerve cell death using mouse hippocampal-derived HT22 cells. The four derivatives (JLK1472, JLK1486, JLK1522 and JLK1535) protected the HT22 cells from death at concentrations ranging from 0.1 to 1 μM. Their action is partially dependent on their ability to act as PPARγ agonists. These analogues also maintain GSH levels suggesting that they have indirect anti-oxidant effects.     

Screening the Toxicity of Ni,Cd, Cu,Ivermectin, and Imidacloprid in a Short-Term Automated Behavioral Toxicity Test with Tubifex tubifex (Müller 1774) (Oligochaeta)

A new automated online toxicity test for screening of short-term effects of chemicals is presented using the freshwater oligochaete Tubifex tubifex in the Multispecies Freshwater Biomonitor? (MFB). Survival and locomotory behavior of the worms were observed during 24 h of exposure to metals (Cd, Cu, Ni), pesticides (Imidacloprid), and pharmaceuticals (Ivermectin). The LC₅₀ values revealed increasing toxicity in the following order: Ni (> 100 mg/l) < Cu (15.2 mg/l) < Cd (4.9 mg/l) < Ivermectin (1.8 mg/l) < Imidacloprid (0.3 mg/l). The EC₅₀ for locomotion showed a similar order of increasing toxicity: Ni (86 mg/l) < Cu (3.8 mg/l) < Ivermectin (2.0 mg/l) < Cd (1.1 mg/l) < Imidacloprid (0.09 mg/l). Toxicity was dependent on both concentration and exposure time. This could be demonstrated in 3d response models and proven in the statistical analysis showing a significant interaction term (C × T) for the experiments with Cu and Ni. T. tubifex proved to be very tolerant, but even then behavioral responses were more sensitive than mortality for Cu, Cd, and Imidacloprid.     

A new troglomorphic species of Harmonicon (Araneae,Mygalomorphae, Dipluridae) from Pará, Brazil,with notes on the genus

A new species of Harmonicon F. O. Pickard-Cambridge, 1896 (Araneae, Dipluridae) is described, from a medium-sized lateritic cave in Parauapebas, Pará, Brazil. The male holotype and only specimen known of H. cerberus sp. n. was found near the entrance of Pequiá cave. This taxon is the fourth species described and the southernmost record for the genus. The new species displays some troglomorphic characteristics, such as reduction and merging of the posterior median and both pairs of lateral eyes and pale yellow to light brown coloration. Both characters are diagnostic when compared to the normal separated eyes and reddish to dark brown of other Harmonicon species. Other diagnostic characteristics are isolated, long, rigid setae distal to the lyra and the shape of the copulatory bulb. This is the second troglomorphic mygalomorph species from Brazil and the first from the Amazonian region.