Ethyl Compounds Research Articles

Bioassay's Directed Isolation-Structure Elucidation and Molecular Docking of Triterpenes from Persea duthiei against Biologically Important Microbial Proteins.

The research work presented in this study is mainly concerned with the bioactivity-directed phytochemical and biological evaluation of Persea duthiei. Persea duthiei is a typical medicinal plant used to treat a variety of ailments such as asthma, edema, and bronchitis. Ethyl acetate, n-hexane, n-butanol, and compounds that are soluble in water were used to examine the antibacterial as well as antifungal capacities of the plant. The antibacterial activity of the soluble parts of ethyl acetate and n-hexane against Escherichia coli, Staphylococcus aureus, Salmonella typhi, and Bacillus subtilis was high, even though there was no activity against Pseudomonas aeruginosa. Likewise, the n-hexane and ethyl acetate fractions were found to have substantial efficacy against several fungal strains such as Aspergillus flavus, Aspergillus fumigates, Fusarium solani, and Aspergillus niger, but not against Candida glabrata. Among the studied fractions, the ethyl acetate soluble fraction had potent antibacterial activity against all of the tested species. This fraction was submitted to phytochemical analysis utilizing various chromatographic methods for the extraction of various pure components. As a consequence, four compounds were isolated, and their structures were elucidated using various spectroscopic methods such as IR, EIMS, HR-EIMS, 1H-NMR, 13C-NMR, NOESY, COSY, HMBC, and HMQC. Urs-12-en-3β-ol (α-amyrine) (1), Urs-12-ene-2α-3β-diol (chamaedrydiol) (2), 3β-hydroxyurs-12-en-28-aldehyde (ursolic aldehyde) (3), and 12-oleanex-3β-ol (β-amyrine) (4) were extracted. Compounds 1, 2, 3, and 4 were examined for antibacterial and antifungal activity and found to have zones of inhibition ranging from 0 to 11 mm against tested bacteria strains and percent inhibition ranging from 0 to 25 percent against fungus strains. Compounds 1 and 4 showed strong efficacy against the investigated fungal species, with a 25% inhibition rate. In the case of antibacterial activity, compounds 4 and 1 showed potent activity with zones of inhibition of 11 mm and 10 mm, respectively. Compounds 2 and 3 were observed to have nonsignificant antimicrobial activity. However, docking studies reflected the complex formation of compound 1 with beta-hydroxyacyl-ACP dehydratase HadAB and S. aureus tyrosyl-tRNA synthetase and compound 2 with topoisomerase II DNA gyrase complex, and they were reported to have antibacterial properties. Similarly, compound 4 was discovered to be well compatible with the lanosterol 14-demethylase (fungal enzyme) and is thus regarded as having antifungal capabilities. Chimera software was used to identify the binding pockets of these complexes. These results indicated that Persea duthiei is a valuable source of medicinal compounds for medication development.

Chemical components of Hyssopus seravshanicus: antioxidant activity, activations of melanogenesis and tyrosinase, and quantitative determination by UPLC-DAD

Hyssopus seravshanicus (Dubj.) Pazij has been used as traditional herb and food due to its wide biological properties. Seventeen known compounds were isolated from the ethyl acetate fraction. Their structures were identified by spectroscopic data and comparison with published data. Among them, 14 ones were identified from H. seravshanicus for the first time. DPPH and ABTS radical scavenging activities for crude ethanol extract (CEE), ethyl acetate fraction (EAF), butanol fraction (BF) and compounds 1, 3, 8, 10, 11 and 13 were performed. CEE, compounds 1, 3, 11 and 13 exhibited potent antioxidant activities. Compound 1 was found to increase the melanin content and tyrosinase activity of B16 melanoma cells. Moreover, the quantitative estimation of compound 1 in the ethyl acetate fraction was carried out by UPLC-DAD and the method was validated. This is the first report on the isolation and bioactivity research on the non-valotile components of H. seravshanicus.

Tridentate pyrrolylzinc compounds: Synthesis, structures, reactivities and catalytic cyclotrimerization reaction of isocyanate

The reactions of ZnEt2 with NNN-tridentate pincer type pyrrolyl ligands, 2,5-bis((dimethylamino)methylene)-1H-pyrrole (HL1), 2,5-bis((pyrrolidin-1-yl)methylene)-1H-pyrrole (HL2) and 2,5-bis((piperidino)methylene)-1H-pyrrole (HL3), afford zinc ethyl compounds [C4H2N(2,5-CH2NMe2)2]ZnC2H5 (1), [C4H2N(2,5-CH2N(CH2)4)2]ZnC2H5 (2), and [C4H2N(2,5-CH2N(CH2)5)2]ZnC2H5 (3) in high yield. Subjecting 1, 2, 3 with one equivalent of tert-butylphenol in THF generated {[C4H2N(2,5-CH2NMe2)2]Zn(O–C6H4-4-tBu)}2 (4), {[C4H2N(2,5-CH2N(CH2)4)2]Zn(O–C6H4-4-tBu)}2 (5), {[C4H2N(2,5-CH2N(CH2)5)2]Zn(O–C6H4-4-tBu)}2 (6), respectively. Each has been characterized by satisfactory C, H and N microanalysis, NMR spectroscopy at ambient temperature, and single crystal X-ray structural analysis. The compounds Et6Zn6O2[C4H2N(2,5-CH2N(CH2)4)2]2 (7) and Et6Zn6O2[C4H2N(2,5-CH2N(CH2)5)2]2 (8) obtained accidentally from zinc ethyl compounds with traces of water. Each of compound 1–6 has been used as initiator for cyclotrimerization of isocyanate, and the organozinc compound 3 shows moderate reactivity toward the cyclotrimerization of isocyanate in Et2O solvent under mild conditions.

Hydroxycinnamic acids used as external acceptors of electrons: an energetic advantage for strictly heterofermentative lactic acid bacteria.

The metabolism of hydroxycinnamic acids by strictly heterofermentative lactic acid bacteria (19 strains) was investigated as a potential alternative energy route. Lactobacillus curvatus PE5 was the most tolerant to hydroxycinnamic acids, followed by strains of Weissella spp., Lactobacillus brevis, Lactobacillus fermentum, and Leuconostoc mesenteroides, for which the MIC values were the same. The highest sensitivity was found for Lactobacillus rossiae strains. During growth in MRS broth, lactic acid bacteria reduced caffeic, p-coumaric, and ferulic acids into dihydrocaffeic, phloretic, and dihydroferulic acids, respectively, or decarboxylated hydroxycinnamic acids into the corresponding vinyl derivatives and then reduced the latter compounds to ethyl compounds. Reductase activities mainly emerged, and the activities of selected strains were further investigated in chemically defined basal medium (CDM) under anaerobic conditions. The end products of carbon metabolism were quantified, as were the levels of intracellular ATP and the NAD(+)/NADH ratio. Electron and carbon balances and theoretical ATP/glucose yields were also estimated. When CDM was supplemented with hydroxycinnamic acids, the synthesis of ethanol decreased and the concentration of acetic acid increased. The levels of these metabolites reflected on the alcohol dehydrogenase and acetate kinase activities. Overall, some biochemical traits distinguished the common metabolism of strictly heterofermentative strains: main reductase activity toward hydroxycinnamic acids, a shift from alcohol dehydrogenase to acetate kinase activities, an increase in the NAD(+)/NADH ratio, and the accumulation of supplementary intracellular ATP. Taken together, the above-described metabolic responses suggest that strictly heterofermentative lactic acid bacteria mainly use hydroxycinnamic acids as external acceptors of electrons.

Design, synthesis, and antitumor screening of certain novel tetrahydroquinoline sulfonamides

Sulfonamide containing molecules are of sound biomedical interest. This work comprises the synthesis and in vitro antitumor testing of new library of 20 such molecules. These compounds were screened for cytotoxic activity against three tumor cell lines MCF-7, HeLa, and HepG2 using MTT assay. The yield was low but all the target compounds exhibited antiproliferative activity better than the standard drug Doxorubicin (CAS-23214-92-8). Seven compounds were more potent and four compounds were as active as the standard drug. There were no great difference between compounds obtained from dimedone and those obtained from cyclohexandione. Also no significant difference found in activity between compounds bearing o-amino ethyl ester side chain and compounds bearing o-amino amide derivatives. However, compounds bearing o-amino-cyano group, although retained considerable activity they were far less active than the preceding two. It was clear that monohydroxy aldehyde derivatives were less active compared with the di and trihydroxy ones.

Oxygen insertion reactions of mixed N-heterocyclic carbene-oxazolinylborato zinc alkyl complexes.

We report the synthesis of a new mixed oxazoline-carbene scorpionate ligand, bis(4,4-dimethyl-2-oxazolinyl)(1-mesitylimidazolyl)phenylborate (PhB(Ox(Me2))2Im(Mes)). Reactions of the protonated form PhB(Ox(Me2))2(Im(Mes)H) with dialkylzinc compounds provide four-coordinate zinc alkyl complexes, and X-ray diffraction studies of the {PhB(Ox(Me2))2Im(Mes)}ZnR (R = Me, Et) compounds show significant structural distortions involving the R groups shifting away from the carbene donor. The reaction of {PhB(Ox(Me2))2Im(Mes)}ZnEt (3) and O2 provides an isolable mononuclear zinc alkylperoxide {PhB(Ox(Me2))2Im(Mes)}ZnOOEt (4), which has been characterized by single crystal X-ray diffraction and (17)O NMR spectroscopy.

Dinuclear zinc hydride supported by an anionic bis(N-heterocyclic carbene) ligand.

Methylene-linked bis(N,N′-di-tert-butylimidazol-2-ylidene) 1 reacted with diethylzinc to give dinuclear zinc ethyl compound 2, which contains a formally anionic bis(carbene) ligand as a result of deprotonation of the methylene bridge. The reaction of 2 with PhSiH3 gave the phenylsilyl compound 3. The zinc hydride 4 was obtained by the reaction of 2 with LiAlH4 or Ph3SiOH followed by treatment with PhSiH3. X-ray diffraction studies show that compounds 2, 3, and 4 all have a similar dimeric structure with D2h symmetry. The reaction of hydride 4 with carbon dioxide and N,N′-diisopropylcarbodiimide gave formato (5) and formamidinato (7) derivatives as a result of the insertion of the heterocumulene into both Zn-H bonds. Reaction with Ph2CO gave the diphenylmethoxy compound 6. Hydride 4 shows catalytic activity in the hydrosilylation of 1,1-diphenylethylene and methanolysis of silanes.

Analysis of Volatile Compounds from Oriental Melons (<i>Cucumis melo L.</i>) Using Headspace SPME Coupled with GC-MS

The quantitative distribution of volatile compounds in the different oriental melon varieties and in the different parts of oriental melon was investigated. Volatile compounds were extracted by solid-phase microextraction (SPME) and analysed by gas chromatography-mass spectrometry (GC-MS). Fifty-four compounds were identified including 33 esters, 3 thioesters, 7 aldehydes, 8 alcohols, 1 acid, 1 ketone and 1 phenol, among which esters were found to be the major constituents in ripe oriental melon. The results showed that ethyl acetate, sulfur-containing esters and compounds containing a straight nine-carbon chain were present at high concentrations in oriental melons, particularly acetic acid phenylmethyl ester. The majority of ester compounds of oriental melon decreased and the aldehyde compounds increased after storage at -20 °C and the distribution of volatiles was also found to be different in the umbilicus, middle and pedicel of an oriental melon Qitian 1 according to their carbon chain length and quantity.

Markers for secondary reactions of migrated crude oil on carbonaceous surfaces

A high abundance of ethyl substituted aromatic hydrocarbons (HCs) relative to their methyl counterparts is an unusual feature of some crude oils. Enhanced stability of ethyl aromatic HCs in the presence of tetralin was observed when individual ethylated compounds were heated with activated carbon in sealed tubes over a range of 170–340°C. In addition, conversion of the common distribution of alkyl aromatic HCs to an unusual distribution, containing a higher relative abundance of ethyl compounds, was demonstrated by way of closed system heating of the aromatic fraction of a crude oil in the presence of activated carbon. The conditions for this unusual process require the presence of hydrogen donor components, which selectively limit the reaction and depletion of ethylated compounds relative to methylated compounds. The phenomenon has been shown to occur for substituted benzenes, naphthalenes, phenanthrenes and biphenyls. Enhanced abundance of ethyl aromatic HCs relative to their methylated counterparts is therefore proposed as an indicator for secondary reactions of migrated crude oil that has undergone thermal alteration after contact with carbonaceous surfaces in sediments. Application of these principles to selected crude oils and sediment extracts from the Carnarvon and Cooper/Eromanga Basins (Australia) indicates that significant secondary reaction of migrated crude oil has occurred.

The 5-HT1A Agonism Potential of Substituted Piperazine-Ethyl-Amide Derivatives Is Conserved in the Hexyl Homologues: Molecular Modeling and Pharmacological Evaluation

In a series of carboxamide and sulphonamide alkyl (ethyl to hexyl) piperazine analogues, although the size of the linker is very different, ethyl and hexyl derivatives possess a high affinity for 5-HT(1A) receptors. Docking studies clearly show that hexyl and ethyl compounds favorably interact with the binding site of the active conformation of 5-HT(1A) receptors, thus confirming a possible agonist profile. This activity is effectively detected in electrophysiological experiments in which all four compounds inhibit the activity of rat dorsal raphe serotonergic neurons.

Metalation and Transmetalation Studies on Ph2PN(iPr)P(Ph)N(iPr)H for Selective Ethene Trimerization to 1-Hexene

Different organometallic compounds of the new aminodiphosphinoamine ligand Ph2PN(iPr)P(Ph)N(iPr)-H (1) are reported that are relevant model complexes for the selective ethene trimerization system consisting of ligand 1, CrCl3(THF)3, and Et3Al that produces 1-hexene in more than 90% yield and high purity. The lithiation of 1 by n-BuLi in the presence of tetramethylethylenediamine (tmeda) yields the mononuclear compound Ph2PN(iPr)P(Ph)N(iPr)-][Li(tmeda)] (2). Without using tmeda the dinuclear species [Ph2N(iPr)P(Ph)N(iPr)-Li]2 (3) was obtained. By addition of a Grignard reagent to the ligand solution the bis(aminodiphosphinoamide)magnesium complex [Ph2PN(iPr)P(Ph)N(iPr)-]2Mg (4) could be isolated. Reaction of Li[CpCrCl3] with 3 leads to the formation of the model compound CpCrCl[-N(iPr)P(Ph)N(iPr)PPh2] (5), which can be alkylated with Na[Et4Al] to form the corresponding ethyl compound CpCrEt[-N(iPr)P(Ph)N(iPr)PPh2] (7). In THF the formation of EtCrCl2(THF)3 (8) directly from the reaction of CrCl3[Ph2PN(iPr)...

Structural Modification Diminishes Toxicity of Lipophilic Longer Mn(III) N-alkylpyridyl porphyrin-based Powerful SOD Mimics: Synthesis, Characterization and SOD-deficient E. coli and S. cerevisiae studies

Oxidative stress is implicated in numerous diseases such as injuries of central nervous system, cancer, diabetes, radiation, ischemia/reperfusion injuries etc. Thus synthetic and natural compounds that could reduce oxidative stress have been actively sought. The structure-activity relationship guided us to successfully develop the ortho cationic Mn(III) Nalkylpyridylporphyrins ; some of them have kcat (O2 •–) as high as of SOD enzymes. Their ability to dismute O2 •– parallels their ability to scavenge ONOO– and suppress cellular redox-based transcriptional activity via inhibition of activation of transcription factors such as NF-κB, HIF-1α and AP-1. Our ongoing in vitro and in vivo studies have helped us to understand how much the type of substituents, the charge, lipophilicity, size, shape, and bulkiness of Mn porphyrins contribute to their therapeutic potency. For example, the 10-fold higher lipophilicity of meta ethyl, MnTE- 3-PyP5+relative to ortho analog, MnTE-2-PyP5+ outbalances its inferior SOD-like activity ; consequently in a SOD-deficient E. coli model of oxidative stress both isomers were equally efficacious. Analog with longer hydrophobic hexyl chains, MnTnHex-2-PyP5+is 13, 500-fold more lipophilic than ethyl porphyrin, MnTE-2-PyP5+, and thus crosses the blood brain barrier at levels enough to make it superior in rodent models of stroke and hemorrhage. However, it possesses strong micellar character which contributes to its higher toxicity relative to shorter ethyl compound, MnTE-2-PyP5+. We herein modified the isomeric hexyl porphyrins, MnTnHex-2(or 3 or 4)-PyP5+ to diminish their toxicity, while maintaining their SOD-like activity. We disrupted their surfactant character by introducing oxygen atom into each of the four alkyl chains. We tested such Mn(III) N-methoxyhexylpyridylporphyrins on efficacy and toxicity in eukaryotic (SOD-deficient yeast S. cerevisiae), and prokaryotic system (SOD-deficient E. coli). While their high SODlike activity was preserved relative to hexyl analogs, the toxicity was dramatically reduced. Whereas 1 μM MnTnHex-3-PyP5+ was already toxic to E. coli, 5 μM methoxyhexyl analog was fully protective. The diminished toxicity of methoxyhexyl relative to hexyl analogs was also found in yeast study. Thus, oxygenmodified Mn(III) N-alkylpyridylporphyrins are strong candidates for clinical development.

Acidity Trends in α,β‐Unsaturated Sulfur, Selenium, and Tellurium Derivatives: Comparison with C‐, Si‐, Ge‐, Sn‐, N‐, P‐, As‐, and Sb‐Containing Analogues

The gas-phase acidity of CH3-CH2XH (X=S, Se, Te), CH2=CHXH (X=S, Se, Te) and PhXH (X=S, Se) compounds was measured by means of Fourier transform ion cyclotron resonance mass spectrometry. To analyze the role that unsaturation plays on the intrinsic acidity of these systems, a parallel theoretical study, in the framework of the G2 and the G2(MP2) theories, was carried out for all ethyl, ethenyl (vinyl), ethynyl, and phenyl O-, S-, Se-, and Te-containing derivatives. Unsaturated compounds are stronger acids than their saturated analogues, because of the strong pi-electron donor ability of the heteroatoms that contributes to a large stabilization of the unsaturated anions. Ethynyl derivatives are stronger acids than vinyl compounds, while phenyl derivatives have an intrinsic acidity intermediate between that of the corresponding vinyl and ethynyl analogues. The CH2=CHXH vinyl compounds (enol-like) behave systematically as slightly stronger acids than their CH3-C(H)X (keto-like) tautomers. Vinyl derivatives are stronger acids than ethyl compounds, because the anion stabilization attributable to unsaturation is greater than that undergone in the neutral compounds. Conversely, the enhanced acidity of the ethynyl derivatives with respect to the vinyl compounds is due to two concomitant effects, the stabilization of the anion and the destabilization of the neutral compound. The acidities of ethyl, vinyl, and ethynyl derivatives containing heteroatoms of Groups 14, 15, and 16 of the periodic table are closely related, and reflect the differences in electronegativity of the CH3CH2-, CH2=CH-, and CH[triple chemical bond]C- groups.

On the use of mixtures of organotin species for catalytic enantioselective ketone allylation--a detective story.

In the presence of enantiopure MTBH(2)(monothiobinaphthol, 2-hydroxy-2[prime or minute]mercapto-1,1[prime or minute]-binaphthyl; 0.2 eq.) quantitative allylation of ArC([double bond]O)Me takes place with impure Sn(CH(2)CH[double bond]CH(2))(4)(prepared from allyl chloride, air-oxidised magnesium and SnCl(4)) to yield tert-homoallylic alcohols in 85-92% ee. In the same process highly purified, or commercial, Sn(CH(2)CH[double bond]CH(2))(4) yields material of only 35-50% ee. The origin of these effects is the presence of small amounts of the compounds, EtSn(CH(2)CH[double bond]CH(2))(3), ClSn(CH(2)CH[double bond]CH(2))(3) ClSnEt(CH(2)CH[double bond]CH(2))(2) in the tetraallyltin sample and the presence of traces of water (which inhibits achiral background reactions). All the triallyl and diallyl species enhance the stereoselectivity in the catalytic allylation reaction, the chlorides more so than the ethyl compound. Hydrolysis of ClSnEt(CH(2)CH[double bond]CH(2))(2) affords crystallographically characterised Sn(4)(mu(3)-O)(mu(2)-Cl)(2)Cl(2)Et(4)(CH(2)CH[double bond]CH(2))(4). Reaction of this latter compound with MTBH(2) leads to the most potent catalyst.

Thorpe-Ingold effects in cyclizations to five-membered and six-membered rings containing planar segments. The rearrangement of N(1)-alkyl-substituted dihydroorotic acids to hydantoinacetic acids in base.

While the gem-dimethyl effect (GDME) is quantitatively similar for cyclizations to cyclopentane and cyclohexane rings and their homomorphs, in systems containing planar segments the GDME is stronger for the formation of five-membered rings. Planar pentagons have smaller angles than planar hexagons and their formation is helped by the decrease in the potential internal bond angle caused by substituents, as suggested by Thorpe and Ingold for small rings. The phenomenon is illustrated with crystal structure data on five-membered hydantoins and six-membered dihydrouracils containing four-atom planar segments. Such a Thorpe-Ingold effect explains the rearrangement in base of N-alkyl substituted dihydroorotic acids 1 to hydantoinacetic acids 3. The reaction involves initial hydrolysis to N-(N-alkylcarbamoyl)aspartic acids 2 and their subsequent cyclization. The unsubstituted N-carbamoylaspartic acid 2a is stable in 1 M KOH, the N(1)-methyl and ethyl compounds 2b and 2c are in equilibrium with the hydantoinacetic acids 3, while the cyclization of the N(1)-isopropyl and cyclohexyl derivatives 2d and 2e is irreversible. Experimental data on equilibria and pK(a)s for ionization of the carboxy and NH groups allow equilibria and rates involving the N-unsubstituted compounds to be estimated and compared with those for the N-alkyl derivatives. The strongest effect is observed on the equilibrium [3(2-)]/2[(2-)], where substitution of H by methyl increases K 600-fold. In vitro the kinetic regioselectivity for acid catalyzed cyclization of N-carbamoylaspartic to hydantoinacetic acid against dihydroorotic acid is only 10:1. This, together with the weaker acidity of the remote carboxyl group, favours cyclization to dihydroorotic acid under biological conditions.

Valence charge concentrations, electron delocalization and beta-agostic bonding in d0 metal alkyl complexes.

In this paper we describe a range of model d(0) metal ethyl compounds and related complexes, studied by DFT calculations and high resolution X-ray diffraction. The concept of ligand-opposed charge concentrations (LOCCs) for d(0) metal complexes is extended to include both cis-and trans-ligand-induced charge concentrations (LICCs) at the metal, which arise as a natural consequence of covalent metal-ligand bond formation in transition metal alkyl complexes. The interplay between locally induced sites of increased Lewis acidity and an ethyl ligand is crucial to the development of a beta-agostic interaction in d(0) metal alkyl complexes, which is driven by delocalization of the M-C bonding electrons. Topological analysis of theoretical and experimental charge densities reveals LICCs at the metal atom, and indicates delocalization of the M-C valence electrons over the alkyl fragment, with depletion of the metal-directed charge concentration (CC) at the alpha-carbon atom, and a characteristic ellipticity profile for the C(alpha)-C(beta) bond. These ellipticity profiles and the magnitude of the CC values at C(alpha) and C(beta) provide experimentally observable criteria for assessing quantitatively the extent of delocalization, with excellent agreement between experiment and theory. Finally, a concept is proposed which promises systematic control of the extent of C-H activation in agostic complexes.

The synthesis and properties of a new linear NPN proligand

Following upon the synthesis of new proligands Me2NCH2XCH2NMe2 (X = O or NMe), we have now prepared quarternised derivatives of the related phosphorus compounds, R2NCH2XCH2NR2 (R = Me or Et, X = PPh). The ethyl compound can act as a phosphorus donor even when the nitrogen atoms are protonated, and we have characterised fully [NiBr4{PhP(CH2NHEt2)2}2][NiBr4] as well as a polymeric adduct of NiBr2 and thf, [{Ni3Br6(thf)5}n].

Extended NMR Study of Spin-Crossover Compounds [Fe(1-alkyl-1H-tetrazole)6](BF4)2 and Their ZnII Analogs

A systematic NMR study was performed on several alkyl–tetrazole complexes of iron(II) and zinc(II) in the 10–300 K temperature range. The experiments were designed to separate the electronic and reorientational phase transitions caused by the spin crossover of the iron compounds from those independent of unpaired electrons. The 19F spectral data on the propyl-tetrazole compounds show that the electronic spin-transition has a strong effect on the spectra, and their behavior can be explained as a combined response to molecular reorientations and the spin transition. For these complexes, second-moment calculations revealed the strength of the interaction between resonant and nonresonant nuclei. Both of the applied NMR methods show irregularities at the temperature region between 70 and 120 K, suggesting the presence of a phase transition. The data also suggest two kinds of reorientational behavior for the BF4 − counter ions. In the iron–ethyl–tetrazole compound, unlike in the propyl–tetrazole complex, a significant amount of unpaired electrons remains in their original high-temperature HS state. Above their effect, the behavior of the nuclear spins of the iron compound is basically governed by the same structural factors as in its zinc analog. The two-exponential behavior of the 1H-T 1 in case of the zinc–methyl–tetrazole compound can be explained on the basis of cross relaxation with the 19F nuclei due to the low 1H/19F ratio. The presence of the two types of methyl reorientation is assumed to be the sign of the two different lattice sites known to be present in the FeII compound. The single-exponential T 1 above T c in the case of [Fe(mtz)6](BF4)2 is consistently the sign of the strength of the paramagnetic relaxation observed in the ethyl and propyl compounds.

Diorganotin(IV)-promoted deamination of amino acids by pyridoxal: SnR 2 2+ complexes of pyridoxal 5′-phosphate and of the Schiff base pyridoxal-pyridoxamine (PLPM), and antibacterial activities of PLPM and [SnR 2(PLPM-2H)] (R=Me, Et, Bu, Ph)

Pyridoxal 5′-phosphate (PLP) and pyridoxal (PL) itself were reacted with diorganotin(IV) derivatives in the presence and absence of aminoacids. With PLP the complexes [SnR 2(PLP-2H)] (R=Me, Et, Bu) were isolated and characterized by EI and FAB mass spectrometry and by IR, Raman and Mössbauer spectroscopy. Reaction mixtures containing PL, valine or glycine and SnR 2(OAc) 2 (R=Me, Et) afforded complexes of the form [SnR 2(PLPM-2H)], where PLPM is the Schiff base formed by condensation of PL and pyridoxamine (PM). PM was presumably formed by transamination between valine or glycine and PL. The PLPM complexes, and their butyl and phenyl analogues, were also synthesized directly by reacting SnR 2O and PLPM, and were characterized by EI and FAB MS, by IR, Raman, Mössbauer and NMR spectroscopy, and in the case of the methyl and ethyl compounds by single-crystal X-ray diffractometry. Crystals of [SnMe 2(PLPM-2H)]·H 2O and [SnEt 2(PLPM-2H)] consist of molecules in which the ligand is bound to the metal through the O atoms of the two deprotonated phenolic hydroxyl groups and the iminic N atom, and the metal exhibits distorted square pyramidal coordination. Both PLPM and its complexes show intense antibacterial activity against Pseudomonas aeruginosa (ATCC27853), but only the complexes exhibit significant activity against the other four bacterial strains assayed, Staphylococcus aureus, Bacillus subtilis, Escherichia coli and a carbapenem-resistant P. aeruginosa strain.

Effects of 5'-alkyl-benzothiadiazides on (R,S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor biophysics and synaptic responses.

Alkyl-substituted benzothiadiazides (BTDs) were tested for their effects on (R,S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors. In excised patches, the 5'-ethyl derivative "D1" blocked the desensitization of AMPA receptor currents during prolonged application of glutamate (EC(50), 36 microM), and it slowed deactivation of responses elicited by 1-ms glutamate pulses greater than 10-fold. [(3)H]Fluorowillardiine binding to rat synaptic membranes was increased by D1 by a factor of 3.6 (EC(50), 17 microM) with a Hill coefficient near 2. In hippocampal slices, the compound reversibly increased excitatory postsynaptic currents and field excitatory postsynaptic potentials (EPSPs) with thresholds around 10 microM. The size of the alkyl substituent influenced both the potency and nature of the drug effect on synaptic currents: 5'-methyl compounds had a 2-fold greater effect on response amplitude than on response duration, whereas 5'-ethyl compounds like D1 caused greater increases in duration than amplitude. In tests with recombinantly expressed AMPA receptor subunits, D1 preferred the glutamate receptor (GluR) subunit GluR4 flip (0.64 microM) over GluR4 flop (5.3 microM); similar affinities but with smaller flip-flop differences were obtained for GluR1 through 3. These results show that D1 and congeners are significantly more potent than the parent compound IDRA-21 and that they differ in two fundamental aspects from cyclothiazide, the most widely studied BTD: 1) D1 markedly increases the agonist affinity of AMPA receptors and 2) it has immediate and large effects on field EPSPs. The large gain in potency conferred by alkyl substitution suggests that the 5' substituent is in intimate contact with the receptor, with the size of the substituent determining the way in which receptor kinetics is changed.