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PubMed2006

DFT studies on the mechanism of allylative dearomatization catalyzed by palladium.

The reaction mechanism of the Pd-catalyzed benzyl/allyl coupling of benzyl chloride with allyltributylstannan, resulting in the dearomatization of the benzyl group, was studied using density functional theory calculations at the B3LYP level. The calculations indicate that the intermediate (eta(3)-benzyl)(eta(1)-allyl)Pd(PH(3)) is responsible for the formation of the kinetically favored dearomatic product. Reductive elimination of the dearomatic product from the intermediate occurs by coupling the C-3 terminus of the eta(1)-allyl ligand and the para-carbon of the eta(3)-benzyl ligand in (eta(3)-benzyl)(eta(1)-allyl)Pd(PH(3)). For comparison, various C-C coupling reaction pathways have also been examined.

Allyl Compounds↗
PubMed2003

Ketone synthesis under neutral conditions. Cu(I) diphenylphosphinate-mediated, palladium-catalyzed coupling of thiol esters and organostannanes.

[reaction: see text] A versatile approach to ketone synthesis is described. The reaction relies on the palladium-catalyzed, copper diphenylphosphinate-mediated coupling of thiol esters with organostannanes under neutral reaction conditions. This reaction complements the previously described coupling of thiol esters with boronic acids that used dual thiophilic-borophilic activation methodology.

Biphenyl Compounds↗
PubMed2005

Determination of metal and organometal trophic bioaccumulation in the benthic macrofauna of the Adour estuary coastal zone (SW France, Bay of Biscay).

A multidisciplinary approach has been adopted in order to investigate the bioaccumulation of metals and organometals in macrobenthic populations. A complete method coupling a sampling strategy and classification of benthic organisms with a performant analytical procedure for the analysis of both metals and organometals has been developed. A single sample preparation method using a TMAH extraction and species specific isotope dilution makes it possible to analyse metals and organometals in the same extract, which is especially interesting for situations where only a limited amount of sample is available. Low detection limits have been obtained in the range of 12-250 pg g(-1) for mercury and butyltin compounds and 0.4-50 ng g(-1) for metals with good precision (1-10% RSD) even for a very low mass of sample (0.02 g). This method has been applied for monitoring contamination and bioaccumulation of metals and organometals as well as the biodiversity and trophic structure of the macrobenthic population of the Adour Estuary (South-West, France). The benthic macrofauna diversity indicates that inner estuarine stations are moderately polluted whereas outer estuarine stations are less impacted. However, metals concentrations in both sediment and benthic biomass do not change drastically between stations. Moreover, the bioaccumulation has been determined in relation to the feeding guild of benthic organisms. The results demonstrate that higher bioaccumulation is generally observed for deposit feeders directly impacted by sediment contamination compared to suspensive feeders and predators. Biomagnification along the trophic levels was highlighted for MMHg but no significant trend was observed for the other metallic compounds.

Animals↗
PubMed2005

Synthesis, spectral characterization and biological studies of some organotin(IV) complexes of L-proline, trans-hydroxy-L-proline and L-glutamine.

New organotin(IV) complexes of the general formula R3Sn(L) (where R=Me, n-Bu and HL=L-proline; R=Me, Ph and HL=trans-hydroxy-L-proline and L-glutamine) and R2Sn(L)2 (where R=n-Bu, Ph and HL=L-proline; R=Ph, HL=trans-hydroxy-L-proline) have been synthesized by the reaction of RnSnCl(4-n) (where n=2 or 3) with sodium salt of the amino acid (HL). n-Bu2Sn(Pro)2 was synthesized by the reaction of n-Bu2SnO with L-proline under azeotropic removal of water. The bonding and coordination behavior in these complexes have been discussed on the basis of IR and 119Sn Mössbauer spectroscopic studies in the solid-state. Their coordination behavior in solution has been discussed with the help of multinuclear (1H, 13C and 119Sn) NMR spectral studies. The 119Sn Mössbauer and IR studies indicate that L-proline and trans-hydroxy-L-proline show similar coordination behavior towards organotin(IV) compounds. Pentacoordinate trigonal-bipyramidal and hexacoordinate octahedral structures, respectively, have been proposed for the tri- and diorganotin(IV) complexes of L-proline and trans-hydroxy-L-proline, in which the carboxylate group acts as bidentate group. L-glutamine shows different coordination behavior towards organotin(IV) compounds, it acts as monoanionic bidentate ligand coordinating through carboxylate and amino group. The triorganotin(IV) complexes of L-glutamine have been proposed to have trigonal-bipyramidal environment around tin. The newly synthesized complexes have been tested for their antiinflammatory and cardiovascular activities. Their LD50 values are >1000 mg kg-1.

Animals↗
PubMed2004

Degradation of the antifouling compound Irgarol 1051 by manganese peroxidase from the white rot fungus Phanerochaete chrysosporium.

Irgarol 1051 (2-methylthio-4-tert-butylamino-6-cyclopropylamino-s-triazine), a derivative of s-triazine herbicide, is an antifouling compound used as an alternative to organotins. The compound is highly persistent and is known to be biodegraded only by the white rot fungus, Phanerochaete chrysosporium. We used partially purified manganese peroxidase (MnP) prepared from P. chrysosporium to evaluate its capacity to degrade Irgarol 1051. MnP degraded Irgarol 1051 to two major products, one identified as M1 (identical to GS26575, 2-methylthio-4-tert-butylamino-6-amino-s-triazine) and the other not identified but with same mass spectrum as M1 and a different ultraviolet spectrum. This report clearly demonstrates that this ligninolytic enzyme is involved in the degradation of Irgarol 1051.

Biodegradation, Environmental↗
PubMed1995

Synthesis and biological activity of five-coordinate platinum(II) complexes including organotin fragments.

The synthesis and characterization of two five-coordinate platinum(II) complexes of general formula [PtCl(SnMe(n)Cl3-n)(2,9-Me2-1,10-phenanthroline) (diethylfumarate)] (n = 1, 2) are described. The bimetallic species were tested on the neuroblastoma cell line SK-N-BE and a considerable inhibition of cellular proliferation was detected; the bimetallic species were also able to induce neuronal differentiation, as did retinoic acid, a well-known neuroblastoma differentiating agent.

Cell Differentiation↗
PubMed2001

[Effects of organonitrogen, carbamate pesticides and others on beta-hexosaminidase release from rat basophilic leukemia cells (RBL-2H3)].

There have been very few reports of the effect of pesticides on immediate allergy. In the previous report, the effect of pyrethroid pesticides and organophosphorus pesticides on immediate allergic reaction was investigated. Subsequently, 12 organonitrogen pesticides, 14 carbamate pesticides and 4 other pesticides were investigated for their effects on the enzyme activity of beta-hexosaminidase as an index of chemical mediator release from rat basophilic leukemia cells (RBL-2H3). Two organonitrogen pesticides, bitertanol and pyridaben, and two organotin pesticides, cyhexatin and fenbutatin oxide, were found to promote beta-hexosaminidase release. Bitertanol non-specifically caused the promotion of chemical mediator release, while the release-promotive action of pyridaben was related to IgE antibody and those of cyhexatin and fenbutatin oxide to cell injury. On the other hand, two organonitrogen pesticides, propiconazole and triadimenol, and imazalil showed release-inhibitory action. These data suggested that some pesticides can affect immediate allergy.

Animals↗
PubMed1999

Triphenyltin acetate-mediated in vitro inactivation of rat liver cytochrome P-450.

The in vitro effects of the organotin (OT) compound triphenyltin acetate (TPTA) on cytochrome P-450 content and functions were investigated in liver microsomes from untreated, phenobarbital (PB)- or beta-naphthoflavone- (betaNAF) pretreated rats. At a concentration of 0.5 mM, TPTA caused a marked loss in the spectrally detectable content of cytochrome P-450 up to 27% of its original value, along with an increase in the inactive form cytochrome P-420. Both effects were most pronounced in betaNAF-treated microsomes, which showed a shift in the hemoprotein absorption maximum from 448 nm to 451 nm, but in all cases TPTA failed to affect either cytochrome b5 or total heme content, or to increase the production of malondialdehyde. These results suggest that lipid peroxidation of microsomal membranes or damage to the heme moiety should be excluded as contributing factors in the hemoprotein loss. TPTA also produced a concentration-related functional inactivation of cytochrome P-450 that was most pronounced in betaNAF-exposed microsomal preparations, as denoted by a striking reduction in the ethoxyresorufin O-deethylase (EROD) activity (IC50 = 0.088 mM). In contrast, the activities of cytochrome P-450-independent microsomal enzymes such as NADPH cytochrome c reductase and indophenyl acetate esterase (IPA-EST) were not markedly affected even by 0.5 mM TPTA (-30%). As assessed by Lineweaver-Burk plots, the mechanism of inhibition appeared to be noncompetitive for IPA-EST and of mixed type (competitive-noncompetitive) for EROD. Among sulfhydryl-containing compounds, dithiothreitol was considerably more effective than albumin and reduced glutathione in preventing cytochrome P-450 inactivation and even was able to partially reverse the hemoprotein damage when added after TPTA; glycerol, which is known to protect the hydrophobic environment of cytochrome P-450, was as effective as albumin. This study indicates that TPTA behaves as an almost specific and powerful in vitro inhibitor of cytochrome P-450-dependent monooxygenases, apparently through the interaction with critical sulfhydryl groups of the hemoprotein.

Aminopyrine N-Demethylase↗
PubMed2002

Organotin contamination in sediments from the Western Mediterranean enclosures following 10 years of TBT regulation.

Organotin (OT) compounds, namely butyl and phenyl, were measured in 38 recent sediments collected in harbours of the Western Mediterranean Sea (Northern: 4 and Southern: 9) and domestic and industrial sewage disposal sites (Northern: 9 and Southern: 1). Butyltins were the predominant tin species identified as being tributyltin (TBT) widespread in the whole area which suggests recent inputs of OTs. The highest levels of TBT were detected in commercial harbours associated with inputs from large vessels (average value: 5.0 microg TBT g(-1). Moreover, relatively high TBT values were also detected in fishing and recreational boating areas (average level ca. 1.0 microg TBTg(-1)). Phenyltin derivatives occurred at lower levels than butyltins being the monophenyltin the predominant compound (average values 45-945 ng g(-1)). The large predominance of the phenyltin degradation products (i.e. mono and diphenyltin) over the parent compound (i.e. triphenyltin) suggests that there are almost no recent inputs of these compounds. Furthermore, a comparative study of the OT occurrence in the sewage sludge disposal sites offshore Barcelona and Almeria (domestic) and into the Tarragona harbour (industrial) shows that domestic primary sewage sludge effluents can contribute to coastal OT pollution (244ng TBT g(-1)). Nevertheless, sewage sludge is a secondary source of OT contamination in the coastal environment in comparison to commercial harbours. In a comparative study with previous data collected in the late 1980s, the present study reveals that OT regulations established in the Mediterranean region in 1991 on the use of TBT-based antifouling paints have been effective in marinas, but reveals a significant TBT contamination in commercial and fishing harbours.

Environment↗
PubMed2001

Toxicity, bioaccumulation, and interactive effects of organotin, cadmium, and chromium on Artemia franciscana.

The effects of three organotin compounds-trimethyltin chloride, dimethyltin dichloride, and dibutyltin diacetate-and two heavy metals-cadmium and hexavalent chromium-on Artemia franciscana mortality are investigated in this study. Of all the compounds tested in this work, trimethyltin chloride was, by far, the most toxic. The toxicity order for the five compounds was trimethyltin chloride > potassium dichromate > dimethyltin dichloride > dibutyltin diacetate > cadmium chloride. The big difference in toxicity between dialkyltin and trialkyltin was not accompanied by an equally big difference in bioaccumulation. At a Sn concentration in water of 10 mg/L, the bioconcentration factor was 50 for dimethyltin dichloride and 75 for trimethyltin chloride. At a Sn concentration in water of 100 mg/L, the bioconcentration factor for 6 for dimethyltin dichloride and 9 for trimethyltin chloride. The interactive effect of trimethyltin chloride and cadmium, as well as that of trimethyltin chloride and chromium, was found to be synergistic. Also found to be synergistic was the interactive effect of trimethyltin chloride with cadmium and chromium applied together.

Animals↗
PubMed2002

Detection of organotin, organomercury, and organolead compounds with a pulsed discharge detector (PDD).

The response of a pulsed discharge detector (PDD) to organometallic compounds in the helium ionization detection (HID) mode was dependant on the number of C atoms in the tested analytes with the limits of detection ranging from 0.7 pg (tetraethyllead (Et(4)Pb)) to 1.2 pg di- n-propyl mercury (Pr(2)Hg)). Response linearity was excellent over three orders of magnitude. Selectivity in the HID mode was enhanced by doping the He discharge gas with argon, although sensitivity dropped threefold. In electron capture detection (ECD) mode, only organolead was detected with a limit of 0.1 pg.

Journal Article↗
PubMed2006

Total synthesis of gymnoconjugatins A and B.

Convergent and efficient syntheses of the microbial natural products gymnoconjugatin A and B are reported and were based on a linchpin coupling strategy using a boron/tin hetero-bis-metallated butadiene system.

Boron Compounds↗