Hydrolysis of benzohydroxamic acids

Ahmad, Afaq; Socha, J.; Večeřa, M.

doi:10.1135/cccc19743293

Cited by 10 publications

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“…This is consistent with the observation that the signal at m / z 355 disappears as the cone voltage B1 is increased from 29 to 46 V, Figures 1 and 2,18 where conversion of increased translational energy to internal energy results in disruption of weak adducts. [22][23][24] The mass spectrum of the iron complex when n = 2 has some of the same features that are observed for n = 8. It is not clear from this experiment just how the chloride is associated with the complex.…”

mentioning

confidence: 76%

Electrospray Mass Spectrometry Study of 1:1 Ferric Dihydroxamates

Caudle¹,

Stevens²,

Crumbliss³

1994

Inorg. Chem.

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In this communication, we report an early example'" of the use of electrospray mass spectrometry (ESMS) to probe the solution structure of transition metal complexes. Iron hydroxamic acid complexes are important due to their relationship to siderophore-mediated iron transport.9 Dihydroxamic acids, such as the siderophore rhodotorulic acid and its synthetic models,lGI4 form 1:l complexes with iron(II1) at low pH. Since this species is an intermediate in the ligand exchange pathway of natural and model ferric dihydroxamates, the elucidation of the 1:l complex as monomer a or dimer b is an important mechanistic consideration.Acid-dependent kinetic studies on the dissociation of the 1: 1 complexes (R = methyl, n = 2-8) gave strong, though not conclusive, evidence that for n I 6, the complex was better formulated as the dimer, b, while the monomer, a, predominates

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confidence: 76%

Electrospray Mass Spectrometry Study of 1:1 Ferric Dihydroxamates

Caudle¹,

Stevens²,

Crumbliss³

1994

Inorg. Chem.

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“…JV-A1kyl-substituted hydroxamic acids seem to be more basic, and two forms of the cation (lb and lc; la not considered) were claimed. 13 In aminohydroxamic acids the amino group is protonated first.14 In this paper we report the gas-phase basicities of acetohydroxamic acid (4) and of its iV-methyl (5) and Omethyl ( 6) derivatives (Table I). In addition to the general interest-placing these compounds into the basicity scale15-we also hoped to get some information concerning the structure of the cation, particularly from a comparison with isosteric amides 7-9.…”

Section: Introductionmentioning

confidence: 93%

The gas-phase basicity of hydroxamic acid derivatives

Decouzon¹,

Exner²,

Gal³

et al. 1992

J. Org. Chem.

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mation of the secondary alcohol 6c would be consistent with a transition state, as in 10, again resembling a structure leading to the more stable carbenium ion 12a. In this situation, however, the more stable carbenium ion site is the primary carbon, because the positive charge can be stabilized by carbon-silicon -bond hyperconjugation (12b).19Experimental Section General Procedures. All steps in the preparation, transfer, and main reactions of the organometallic reagents studied here were conducted under an atmosphere of anhydrous and oxygen-free argon. All solvents and apparatus were likewise freed of traces of dissolved or adsorbed moisture and oxygen and then maintained under argon. Methods and techniques for working under anhydrous and anaerobic conditions and for conducting standard chromatographic and spectrometric analyses have been described previously.20Starting Materials and Products. Diisobutylaluminum hydride and triisobutylaluminum were obtained as neat reagents from Texas Alkyls Inc., Deer Park, TX. Diisobutylaluminum sec-butoxide was generated in situ by the cautious treatment of i-Bu2AlH in heptane with 1 equiv of sec-butyl alcohol.1,2-Epoxydecane and styrene oxide were commercially available and (epoxyethyl)triphenylsilane was prepared from the epoxidation of triphenylvinylsilane with m-chloroperbenzoic acid.21The reaction products 1-decanol, 2-decanol, 1-phenyl-l-ethanol, and 2-phenyl-l-ethanol were purchased, while the l-(triphenylsilyl)-l-ethanol and 2-(triphenylsilyl)-l-ethanol were synthesized by known procedures.22 (19) Any electrophilic attack on 5c, such as where E = MeAlCl2, is known to favor formation of the carbenium ion ß to silicon jse.

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“…The addition of an acetohydroxamic acid side chain to the N-1 nitrogen of 3-nitropyrazole did indeed increase the chemosensitizing effectiveness of the lead compound, however the relative chemosensitizing effectiveness of the compounds did not agree with the expected rates for the Lossen rearrangement. By extrapolation from the hydrolysis of benzohydroxamic acids described by Ahmad et al [21] and Ashfaq et al [22], the p-NO 2 benzoyl derivative (8) would have been expected to have the highest rate of rearrangement among the compounds in the current series, and according to the hypothesis should therefore have been the most effective chemosensitizing agent. However, in terms of chemosensitizing activity, 8 was equivalent to the acetyl (7) and propionyl (6) analogues and inferior to both the benzoyl (9) and pivaloyl (10) derivatives; all of which have less favorable leaving groups.…”

Section: Discussionmentioning

confidence: 99%

Enhancement of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) toxicity by acetohydroxamic acid analogues of 3-nitropyrazole in vitro

Mulcahy¹,

Wustrow²,

Hark³

et al. 1987

Invest New Drugs

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A series of acetohydroxamic acid derivatives of 3-nitropyrazole were synthesized and evaluated for their ability to potentiate (chemosensitization) the activity of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) against EMT-6 mouse mammary tumor cells in vitro. The compounds were designed to test the hypothesis that the chemosensitizing activity of the analogues would be proportional to the rate of isocyanate formation via a Lossen rearrangement, in part a function of the leaving group at the N terminus of each acetohydroxamate. Substitution of acetohydroxamic acid side chains at the N-1 position of the parent 3-nitropyrazole resulted in compounds which were preferentially toxic to cells treated under hypoxic conditions, and which were capable of enhancing the toxicity of CCNU in hypoxia. As was observed for cytotoxicity, the enhancement of CCNU toxicity by these sensitizing agents was significantly reduced under aerobic treatment conditions. A strong correlation was established between hypoxic toxicity and chemosensitizing potency. The activity of the analogue, however, was not proportional to their excepted rates of Lossen rearrangement. Nevertheless, several potent chemosensitizing compounds were identified; some of which were 10-50 X's more potent on a molar basis than Misonidazole, the reference chemosensitizing compound.

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Hydrolysis of benzohydroxamic acids

Cited by 10 publications

References 0 publications

Electrospray Mass Spectrometry Study of 1:1 Ferric Dihydroxamates

Electrospray Mass Spectrometry Study of 1:1 Ferric Dihydroxamates

The gas-phase basicity of hydroxamic acid derivatives

Enhancement of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU) toxicity by acetohydroxamic acid analogues of 3-nitropyrazole in vitro

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