Regiodivergent Synthesis of 3,4- and 4,5-Disubstituted N-Methylpyrazoles from 4-Acyl-1H-pyrrole-2,3-dione and Methylhydrazine.

A simple, efficient and highly regioselective method for the preparation of 3,4- and 4,5-disubstituted N-methylpyrazoles in a one-pot procedure is reported. The methodology developed was based on the regiochemical control of the reaction of 4-acyl-1H-pyrrole-2,3-diones and methylhydrazine with an influence of the addition or absence of acid and the substrate structure.

Vibrational Properties and DFT Calculations of Perovskite-Type Methylhydrazinium Manganese Hypophosphite.

Recently discovered hybrid perovskites based on hypophosphite ligands are a promising class of compounds exhibiting unusual structural properties and providing opportunities for construction of novel functional materials. Here, we report for the first time the detailed studies of phonon properties of manganese hypophosphite templated with methylhydrazinium cations ([CH3NH2NH2][Mn(H2PO2)3]). Its room temperature vibrational spectra were recorded for both polycrystalline sample and a single crystal. The proposed assignment based on Density Functional Theory (DFT) calculations of the observed vibrational modes is also presented. It is worth noting this is first report on polarized Raman measurements in this class of hybrid perovskites.

Metabolomics and cytotoxicity of monomethylhydrazine (MMH) and (E)-1,1,4,4-tetramethyl-2-tetrazene (TMTZ), two liquid propellants.

Hydrazine-based liquid propellants are routinely used for space rocket propulsion, in particular monomethylhydrazine (MMH), although such compounds are highly hazardous. For several years, great efforts were devoted to developing a less hazardous molecule. To explore the toxicological effects of an alternative compound, namely (E)-1,1,4,4-tetramethyl-2-tetrazene (TMTZ), we exposed various cellular animal and human models to this compound and to the reference compound MMH. We observed no cytotoxic effects following exposure to TMTZ in animal, as well as human models. However, although the three animal models were unaffected by MMH, exposure of the human hepatic HepaRG cell model revealed that apoptotic cytotoxic effects were only detectable in proliferative human hepatic HepaRG cells and not in differentiated cells, although major biochemical modifications were uncovered in the latter. The present findings indicate that the metabolic mechanisms of MMH toxicity is close to those described for hydrazine with numerous biochemical alterations induced by mitochondrial disruption, production of radical species, and aminotransferase inhibition. The alternative TMTZ molecule had little impact on cellular viability and proliferation of rodent and human dermic and hepatic cell models. TMTZ did not produce any metabolomic effects and appears to be a promising putative industrial alternative to MMH.

Mechanistic insights into the ANRORC-like rearrangement between methylhydrazine and 1,2,4-oxadiazole derivatives.

We herein present the first in-depth theoretical study devoted to elucidate the mechanism of the reaction between 1,2,4-oxadiazole derivatives and methylhydrazine. For this purpose, the reaction between methylhydrazine and some polyfluoroaryl-1,2,4-oxadiazoles has been employed as a model reaction. The analysis of the potential energy surface (PES) indicates that the most favorable path involves an initial amine attack at the C(2') site of the aryl moiety to yield an aryl-hydrazine intermediate whose thermodynamic stability appears as the main determinant of the favored reaction path. Next, the cyclization step leading to a spiro intermediate through a favored 5-exo-trig process appears as the rate determining step. Additionally, this study highlights the relevance of the torsional strain effects on the favored ANRORC pathway. Finally, both the origins of the substituent effects on the regioselectivity patterns as well as the need of using a large excess of nucleophile to afford the favored ANRORC pathway are discussed.

Pervaporation performance of PPO membranes in dehydration of highly hazardous mmh and udmh liquid propellants.

Polyphenylene oxide (PPO) membranes synthesized from 2,6-dimethyl phenol monomer were subjected to pervaporation-based dehydration of the highly hazardous and hypergolic monomethyl hydrazine (MMH) and unsymmetrical dimethyl hydrazine (UDMH) liquid propellants. Membranes were characterized by TGA, DSC and SEM to study the effect of temperature besides morphologies of surface and cross-section of the films, respectively. Molecular dynamics (MD) simulation was used to study the diffusion behavior of solutions within the membrane. CFD method was employed to solve the governing mass transfer equations by considering the flux coupling. The modeling results were highlighted by the experimental data and were in good agreement. High separation factors (35-70) and reasonable water fluxes (0.1-0.2 kg/m(2)h) were observed for separation of the aqueous azeotropes of MMH (35 wt%) and UDMH (20 wt%) and their further enrichment to >90% purity. Effect of feed composition, membrane thickness and permeate pressure on separation performance of PPO membranes were investigated to determine optimum operating conditions.

Discovery of S-adenosyl-L-homocysteine hydrolase inhibitors based on non-adenosine analogs.

High throughput screening using Automated Ligand Identification System (ALIS) resulted in the discovery of a new series of S-adenosyl-L-homocysteine hydrolase inhibitors based on non-adenosine analogs. The optimization campaign led to very potent and competitive compound 39 with a Ki value of 1.5 nM. Compound 39 could be a promising lead compound for research to reduce elevated homocysteine levels.

Developing a trace level GC-MS method for detecting methylhydrazine in an experimental drug substance.

Methylhydrazine (NH(2)NHCH(3), CAS 60-34-4) is a highly reactive reducing agent used as an intermediate for synthesizing an experimental drug substance. Methylhydrazine is a known mutagen, an animal carcinogen, and a suspected human carcinogen. A gas chromatography-mass spectrometry method was developed as a limit test method for analyzing trace levels of methylhydrazine in the experimental drug substance. The method utilizes acetone as a dissolving solvent for the drug substance and a derivatizing agent for methylhydrazine in the meantime, thus eliminating the need for post-derivatization sample clean-up prior to analysis. The gas chromatographic (direct injection) conditions provide good separation for the acetone-methylhydrazine derivative (acetone methylhydrazone) from matrix interference, and mass spectrometric detection (selected ion monitoring mode, m/z 86) allows sufficient sensitivity for detecting 1 part per million methylhydrazine relative to the drug substance.

CH3NHNH2 + OH reaction: mechanism and dynamics studies.

A direct dynamics study was carried out for the multichannel reaction of CH(3)NHNH(2) with OH radical. Two stable Conformers (I, II) of CH(3)NHNH(2) are identified by the rotation of the -CH(3) group. For each conformer, five hydrogen-abstraction channels are found. The reaction mechanisms of product radicals (CH(3)NNH(2) and CH(3)NHNH) with OH radical are also investigated theoretically. The electronic structure information on the potential energy surface is obtained at the B3LYP/6-311G(d,p) level and the energetics along the reaction path is refined by the BMC-CCSD method. Hydrogen-bonded complexes are presented at both the reactant and product sides of the five channels, indicating that the reaction may proceed via an indirect mechanism. The influence of the basis set superposition error (BSSE) on the energies of all the complexes is discussed by means of the CBS-QB3 method. The rate constants of CH(3)NHNH(2) + OH are calculated using canonical variational transition-state theory with the small-curvature tunneling correction (CVT/SCT) in the temperature range of 200-1000 K. Slightly negative temperature dependence of rate constant is found in the temperature range from 200 to 345 K. The agreement between the theoretical and experimental results is good. It is shown that for Conformer I, hydrogen-abstraction from -NH- position is the primary pathway at low temperature; the hydrogen-abstraction from -NH(2) is a competitive pathway as the temperature increases. A similar case can be concluded for Conformer II. The overall rate constant is evaluated by considering the weight factors of each conformer from the Boltzmann distribution function, and the three-term Arrhenius expressions are fitted to be k(T) = 1.6 x 10(-24)T(4.03)exp (1411.5/T) cm(3) molecule(-1) s(-1) between 200-1000 K.

Formation and decay of tetrazane derivatives--a Car-Parrinello molecular dynamics study.

The complications during flight 510 of the Ariane Project were ascribed to problems in the upper stage engine that employs the bipropellant monomethylhydrazine (MMH) and nitrogen tetroxide (NTO). This has led to the question what conditions or reactions possibly cause an uncontrolled behaviour in the combustion process of MMH/NTO. We use first-principles molecular dynamics to investigate the reactions of the hypergolic mixture in different chemical situations. It was possible to observe the ultrafast redox reaction between the reactants on the timescale of an unconstrained simulation. We show that electrostatic attraction is crucial for the understanding of this reaction. Besides a cold reaction preceding the ignition, a reaction path leading to the highly reactive compound dimethyltetrazane could be identified.

Gas chromatography-mass spectrometry determination of the pentafluorobenzoyl derivative of methylhydrazine in false morel (Gyromitra esculenta) as a monitor for the content of the toxin gyromitrin.

The main toxic compound found in false morel (Gyromitra esculenta) is acetaldehyde-N-methyl-N-formylhydrazone (gyromitrin). This paper describes a method of determining the total hydrazones content based on acid hydrolysis of gyromitrin and other related hydrazones in air-dried false morel followed by derivatisation of methylhydrazine with pentafluorobenzoyl chloride. The derivative, tris-pentafluorobenzoyl methylhydrazine (tris-PFB-MH) is analyzed by gas chromatography-mass spectrometry. The overall precision of the method is better than 10% (relative standard deviation) for 0.5 ng/microl methylhydrazine in solution. The minimum detectable concentration of methylhydrazine (tris-PFB-MH) by this method is estimated to be approximately 12 pg/microl, which is equal to 0.3 microg/g dry matter (DM) of false morel.

Determination of hydrazine, monomethylhydrazine, 1,1-dimethylhydrazine, and 1,2-dimethylhydrazine by nonaqueous capillary electrophoresis with amperometric detection.

The present study is concerned with the application of nonaqueous capillary electrophoresis (NACE) with electrochemical detection (ED) to the separation and quantitative determination of hydrazine (Hy) and its methyl derivatives. The best performance of NACE-ED was found when using 4 mM sodium acetate/10 mM acetic acid/methanol: acetonitrile = 1:2 as the running buffer, with a bare platinum working electrode set at +1.0 V in an end-column amperometric detection cell. The choice and ratio of suitable solvents for the separation and injection media played an essential role for the performance characteristics of the method. The limits of detection for Hy, methylhydrazine, symmetrical dimethylhydrazine, and unsymmetrical dimethylhydrazine were 5, 2, 12, and 1 ng/mL, respectively. This is between one and two orders of magnitude lower than that achieved by previously reported CE-ED methods in aqueous buffer systems in conjunction with various types of chemically modified electrodes. The practical utility of the new NACE-ED methodology is demonstrated in terms of the determination of traces of Hys in spiked environmental samples containing a wide range of explosives and related compounds.

Mycotoxins revisited: Part II.

Mushrooms are ubiquitous in nature. They are an important source of nutrition, however, certain varieties contain chemicals that can be highly toxic to humans. Industrially cultivated mushrooms are historically very safe, whereas foraging for mushrooms or accidental ingestion of mushrooms in the environment can result in serious illness and death. The emergency department is the most common site of presentation for patients suffering from acute mushroom poisoning. Although recognition can be facilitated by identification of a characteristic toxidrome, the presenting manifestations can be variable and have considerable overlap with more common and generally benign clinical syndromes. The goal of this two-part article is to review the knowledge base on this subject and provide information that will assist the clinician in the early consideration, diagnosis and treatment of mushroom poisoning. Part I reviewed the epidemiology and demographics of mushroom poisoning, the physical characteristics of the most toxic varieties, the classification of the toxic species, and presented an overview of the cyclopeptide-containing mushroom class. Part II is focused on the presentation of the other classes of toxic mushrooms along with an up-to-date review of the most recently identified poisonous varieties.

Enhanced biodegradation of methylhydrazine and hydrazine contaminated NASA wastewater in fixed-film bioreactor.

The aerobic biodegradation of National Aeronautics and Space Administration (NASA) wastewater that contains mixtures of highly concentrated methylhydrazine/hydrazine, citric acid and their reaction product was studied on a laboratory-scale fixed film trickle-bed reactor. The degrading organisms, Achromobacter sp., Rhodococcus B30 and Rhodococcus J10, were immobilized on coarse sand grains used as support-media in the columns. Under continuous flow operation, Rhodococcus sp. degraded the methylhydrazine content of the wastewater from a concentration of 10 to 2.5 mg/mL within 12 days and the hydrazine from approximately 0.8 to 0.1 mg/mL in 7 days. The Achromobacter sp. was equally efficient in degrading the organics present in the wastewater, reducing the concentration of the methylhydrazine from 10 to approximately 5 mg/mL within 12 days and that of the hydrazine from approximately 0.8 to 0.2 mg/mL in 7 days. The pseudo first-order rate constants of 0.137 day(-1) and 0.232 day(-1) were obtained for the removal of methylhydrazine and hydrazine, respectively, in wastewater in the reactor column. In the batch cultures, rate constants for the degradation were 0.046 and 0.079 day(-1) for methylhydrazine and hydrazine respectively. These results demonstrate that the continuous flow bioreactor afford greater degradation efficiencies than those obtained when the wastewater was incubated with the microbes in growth-limited batch experiments. They also show that wastewater containing hydrazine is more amenable to microbial degradation than one that is predominant in methylhydrazine, in spite of the longer lag period observed for hydrazine containing wastewater. The influence of substrate concentration and recycle rate on the degradation efficiency is reported. The major advantages of the trickle-bed reactor over the batch system include very high substrate volumetric rate of turnover, higher rates of degradation and tolerance of the 100% concentrated NASA wastewater. The results of the present laboratory scale study will be of great importance in the design and operation of an industrial immobilized biofilm reactor for the treatment of methylhydrazine and hydrazine contaminated NASA wastewater.

Active-site structure of the soluble quinoprotein glucose dehydrogenase complexed with methylhydrazine: a covalent cofactor-inhibitor complex.

Soluble glucose dehydrogenase (s-GDH) from the bacterium Acinetobacter calcoaceticus is a classical quinoprotein. It requires the cofactor pyrroloquinoline quinone (PQQ) to catalyze the oxidation of glucose to gluconolactone. The precise catalytic role of PQQ in s-GDH and several other PQQ-dependent enzymes has remained controversial because of the absence of comprehensive structural data. We have determined the crystal structure of a ternary complex of s-GDH with PQQ and methylhydrazine, a competitive inhibitor of the enzyme. This complex, refined at 1.5-A resolution to an R factor of 16.7%, affords a detailed view of a cofactor-binding site of s-GDH. Moreover, it presents the first direct observation of covalent PQQ adduct in the active-site of a PQQ-dependent enzyme, thereby confirming previous evidence that the C5 carbonyl group of the cofactor is the most reactive moiety of PQQ.

Iron release in erythrocytes from patients with beta-thalassemia.

Our previous studies have shown that iron is released in a free (desferrioxamine-chelatable) form when erythrocytes undergo oxidative stress (incubation with oxidizing agents or aerobic incubation in buffer for 24-60 h (a model of rapid in vitro ageing)). The release is accompanied by oxidative alterations of membrane proteins as well as by the appearance of senescent antigen, a signal for termination of old erythrocytes. In hemolytic anemias by hereditary hemoglobin alterations an accelerated removal of erythrocytes occurs. An increased susceptibility to oxidative damage has been reported in beta-thalassemic erythrocytes. Therefore we have investigated whether an increased iron level and an increased susceptibility to iron release could be observed in the erythrocytes from patients with beta-thalassemia. Erythrocytes from subjects with thalassemia intermedia showed an extremely higher content (0 time value) of free iron and methemoglobin as compared to controls. An increase, although non-statistically-significant, was seen in erythrocytes from subjects with thalassemia major. Upon aerobic incubation for 24 h the release of iron in beta-thalassemic erythrocytes was by far greater than in controls, with the exception of thalassemia minor. When the individual values for free iron content (0 time) seen in thalassemia major and intermedia were plotted against the corresponding values for HbF, a positive correlation (P < 0.001) was observed. Also, a positive correlation (P < 0.01) was seen between the values for free iron release (24 h incubation) and the values for HbF. These results suggest that the presence of HbF is a condition favourable to iron release. Since in beta-thalassemia the persistance of HbF is related to the lack or deficiency of beta chains and therefore to the excess of alpha chains, the observed correlation between free iron and HbF, is consistent with the hypothesis by others that excess of alpha chains represents a prooxidant factor.

Detection of hydrazine, methylhydrazine and isoniazid by capillary electrophoresis with a 4-pyridyl hydroquinone self-assembled microdisk platinum electrode.

Capillary electrophoresis (CE)/electrochemical detection (EC) for the simultaneous detection of hydrazine, methylhydrazine, and isoniazid has been developed with a 4-pyridyl hydroquinone self-assembled microdisk platinum electrode. Such an electrode has very high catalytic ability for hydrazines and they could be detected even at 0.0 V. The responses for hydrazine, methylhydrazine, and isoniazid are linear over 3 orders of detected concentration and of magnitude of 0.2-400 microM, 0.2-400 microM, 0.5 microM-2 mM, with correlation coefficients of 0.9998, 0.9991, and 0.9982, respectively. And they could be detected to levels of 0.1, 0.1 and 0.2 microM, respectively. This modified electrode was found to be very stable and reproducible when continuously used as detector for capillary electrophoresis for period of at least 4 weeks with no apparent loss of response.

Contribution of hydrazines-derived alkyl radicals to cytotoxicity and transformation induced in normal c-myc-overexpressing mouse fibroblasts.

Several hydrazine derivatives (HD) tested so far have pharmacological activities, but many also have toxic side effects, including carcinogenesis. Their toxicity has been ascribed to carbocations (via formation of azoxy intermediates), alkyl radicals or reactive oxygen species. Cytotoxicity and transformation by carbocations is widely accepted, but the role of alkyl radicals is still questioned. We have investigated the cytotoxicity of HD to mouse fibroblasts in three activation systems in which enhanced alkyl radical formation is demonstrated by electron spin resonance/spin-trapping. Cytotoxicity was assayed by inhibition of [3H-methyl]thymidine uptake into DNA of Balb/c 3T3 and/or Myc 9E fibroblasts (normal Balb/c 3T3 cells over-expressing the c-myc proto-oncogene). Based on the results obtained in the cytotoxicity assays we also investigated the transforming potential of procarbazine (PCZ) and methylhydrazine (MeH) activated by horseradish peroxidase (HRP) using the Myc 9E cell line, which aims at the activation of a second cooperating oncogene. Our results show that: (i) cytotoxicity of HD to mouse fibroblasts is increased by HRP activation of MeH, phenelzine and PCZ, which displayed enhanced alkyl radical formation, but not of 1,2-dimethylhydrazine (DMH), which did not produce increased alkyl radical formation under these conditions; (ii) cytotoxicity of neutrophil-activated MeH (producing a 10-fold higher concentration of methyl radicals), is more pronounced than DMH; (iii) MeH and DMH activated by prolonged auto-oxidation in 24-h incubations have comparable cytotoxicity and alkyl radical formation; and (iv) PCZ and MeH activation by HRP to alkyl radicals increased the transformation induced in Myc 9E cells. Taken together, our results strongly support a role for hydrazine-derived alkyl radicals in HD-induced cytotoxicity and cell transformation.

Determination of monomethylhydrazine with a high-throughput, all-fiber near-infrared spectrometer based on an integrated acoustooptic tunable filter and an erbium-doped fiber amplifier.

A novel integrated acoustooptic tunable filter (IAOTF) has been developed. This tunable filter is based on the Bragg interactions between waveguide and surface acoustic waves. Compared to (bulk) AOTF, its advantage include all-fiber construction, smaller size, narrower spectral resolution (1.7 nm), higher diffraction efficiency (37%), and lower rf power requirement (150 mW). A relatively narrow spectral tuning range (about 80 nm) is the only drawback for this integrated tunable filter. However, this disadvantage was overcome by judiciously using the filter for measurements in which its tuning range is coincident with the light source and also with absorption bands of analytes. In fact, an all-fiber, compact, high-throughput near-infrared spectrophotometer has been successfully constructed by synergistic use of this integrated AOTF and the erbium-doped fiber amplifier (EDFA), which has been shown to provide high intensity and wide spectral band-width in the near-infrared region from 1500 to 1600 nm. This spectral region is particularly useful for the determination of samples which have O-H and/or N-H groups. The all-fiber nature, compactness, high throughput, and high sensitivity of this spectrophotometer make it particularly suitable for on-line and real-time detection of trace gases in hostile environments, including leak detection of monomethylhydrazine (at a limit of detection of 191 ppm), which is often used as the hypergolic propellant for the space shuttle thruster systems.

Exon-specific DNA hypomethylation of the p53 gene of rat colon induced by dimethylhydrazine. Modulation by dietary folate.

Folate deficiency enhances colorectal carcinogenesis in dimethylhydrazine-treated rats. Folate is an important mediator of DNA methylation, an epigenetic modification of DNA that is known to be dysregulated in the early stages of colorectal cancer. This study investigated the effect of dimethylhydrazine on DNA methylation of the colonic p53 gene and the modulation of this effect by dietary folate. Sprague-Dawley rats were fed diets containing 0, 2, 8, or 40 mg of folate/kg of diet. Five weeks after diet initiation, dimethylhydrazine was injected weekly for fifteen weeks. Folate-depleted and folate-replete control animals did not receive dimethylhydrazine and were fed the 0- and 8-mg folate diets, respectively. The extent of p53 methylation was determined by a quantitative HpaII-polymerase chain reaction. In exons 6 and 7, significant p53 hypomethylation was observed in all dimethylhydrazine-treated rats relative to controls (P < 0.01), independent of dietary folate. In exon 8, significant p53 hypomethylation was observed only in the dimethylhydrazine-treated folate-depleted rats compared with controls (P = 0.038) and was effectively overcome by increasing levels of dietary folate (P = 0.008). In this model, dimethylhydrazine induces exon-specific p53 hypomethylation. In some exons, this occurs independent of dietary folate, and in others, increasing levels of dietary folate effectively override the induction of hypomethylation in a dose-responsive manner. This may be a mechanism by which increasing levels of dietary folate inhibit colorectal carcinogenesis.