Search results for "Phenylhydrazine"
showing 8 items of 8 documents
Nitrogen-15 NMR Studies on Hydrazines. 2— Substituent Effect Analysis inortho-Substituted Phenylhydrazines and Anilines
1996
15N and 13C NMR spectra of some ortho-substituted phenylhydrazines were measured at natural isotope abundance in DMSO-d6 solutions. The substituent present exerts a larger effect on the chemical shift of the nitrogen atom directly bound to the aromatic ring (N-1), the second one (N-2) showing an attenuated trend of similar sign. Contrary to what observed for para and meta isomers, the cross-correlation between N-1 and N-2 SCS values of ortho-substituted phenylhydrazines is not satisfactory; on the other hand, N-1 SCSs show a reasonably good linear regression with the σR− constants. As expected, no correlation was found between N-1 and C-1 or H-1 SCS values. Correlations between 13C and 15N …
Determination of carbonyl compounds in particulate matter PM2.5 by in-tube solid-phase microextraction coupled to capillary liquid chromatography/mas…
2013
Abstract In this paper, a new procedure based on in-tube solid phase microextraction (IT-SPME)-capillary liquid chromatography hyphenated to mass spectrometry detection by using microelectrospray ionisation (CapLC–MS), has been reported. The device was proposed to quantify 12 carbonyl compounds (10 aliphatic aldehydes, an unsaturated aldehyde and a ketone) derivatized with 2,4-dinitrophenylhidrazine (DNPH) reagent in aqueous extracts of PM 2.5 . This methodology involves the on-line preconcentration of DNPH-carbonyl compounds derivatives coupled to the CapLC–MS system, efficiently providing appropriate sensitivity for the determination of the target analytes. Detection limits for the analyt…
Detection of oxidative mutagenesis by isoniazid and other hydrazine derivatives in Escherichia coli WP2 tester strain IC203, deficient in OxyR: stron…
1998
Abstract Strain IC203, deficient in the OxyR function, was sensitive to both cytotoxic and mutagenic effects of isoniazid (INH) whereas its parent, WP2 uvrA /pKM101, was resistant to these effects. Four other hydrazine compounds, hydrazine hydrate (HZH), phenylhydrazine (PHZ), hydralazine (HLZ) and nialamide (NLD), were mutagenic in WP2 uvrA /pKM101. Increases in mutagenicity were observed in IC203 for HZH and PHZ but not for HLZ and NLD. Growth inhibition zones by HZH, PHZ and NLD were larger in IC203 than in WP2 uvrA /pKM101. The enhancements in the effects of INH, HZH and PHZ in IC203 with respect to its oxyR + parent are considered to be caused by the production of reactive oxygen speci…
15N NMR: Substituent effect analysis inpara-andmeta-substituted phenylhydrazines
1994
15N NMR spectra of phenylhydrazine and of 14 para- and meta-substituted phenylhydrazines were measured at natural isotope abundance in DMSO-d6 solution. The substituent present exerts a larger influence on the chemical shift of the nitrogen atom directly bound to the aromatic ring (N-1) than on the second one (N-2), which shows an attenuated and inverted trend. The chemical shifts of N-1 and N-2 give a good cross correlation in both series of compounds if p-NO2 and m-F derivatives are excluded from the correlations of para- and meta-substituted phenylhydrazines, respectively. Moreover, N-1 SCS values show good linear correlations with Hammett substituent constants, with SCSs of directly bou…
Improved Regioselectivity in Pyrazole Formation through the Use of Fluorinated Alcohols as Solvents: Synthesis and Biological Activity of Fluorinated…
2008
The preparation of N-methylpyrazoles is usually accomplished through reaction of a suitable 1,3-diketone with methylhydrazine in ethanol as the solvent. This strategy, however, leads to the formation of regioisomeric mixtures of N-methylpyrazoles, which sometimes are difficult to separate. We have determined that the use of fluorinated alcohols such as 2,2,2-trifluoroethanol (TFE) and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as solvents dramatically increases the regioselectivity in the pyrazole formation, and we have used this modification in a straightforward synthesis of fluorinated analogs of Tebufenpyrad with acaricide activity. Fil: Fustero, Santos. Universidad de Valencia; España Fil…
Indirect oxidation of amino acid phenylhydrazides by mushroom tyrosinase.
2006
We have investigated oxidation of amino acid phenylhydrazides by mushroom tyrosinase in the presence of 4-tert-butylcatechol and N-acetyl-l-tyrosine. Spectrophotometric measurements showed gradual disappearance of 4-tert-butyl-o-benzoquinone, generated by oxidation of 4-tert-butylcatechol with sodium periodate, after addition of amino acid phenylhydrazides. However, the presence of the phenylhydrazides did not influence the concentration of 4-tert-butyl-o-benzoquinone formed during enzymatic oxidation. Oxygen consumption measurements demonstrated that in a mixture both compounds were oxidized but the reaction rate was proportional to the concentration of the catechol. In the oxidation of N-…
Heterocyclic rearrangements. Phenylhydrazones andN-methyl-N-phenylhydrazones of 3-acylisoxazoles
1983
The reaction of 3-benzoyl-5-phenylisoxazole (4) and 3-acetyl-5-methylisoxazole (5) with phenylhydrazine and N-methyl-N-phenylhydrazine has been investigated and the reactivity of (E)- and (Z)-phenylhydrazones and N-methyl-N-phenylhydrazones has been studied.
Discovery of a new class of sortase a transpeptidase inhibitors to tackle gram-positive pathogens: 2-(2-phenylhydrazinylidene)alkanoic acids and rela…
2016
A FRET-based random screening assay was used to generate hit compounds as sortase A inhibitors that allowed us to identify ethyl 3-oxo-2-(2-phenylhydrazinylidene)butanoate as an example of a new class of sortase A inhibitors. Other analogues were generated by changing the ethoxycarbonyl function for a carboxy, cyano or amide group, or introducing substituents in the phenyl ring of the ester and acid derivatives. The most active derivative found was 3-oxo-2-(2-(3,4dichlorophenyl)hydrazinylidene)butanoic acid (2b), showing an IC50 value of 50 µM. For a preliminary assessment of their antivirulence properties the new derivatives were tested for their antibiofilm activity. The most active compo…