Organische Metallkomplexe, III. Synthesen und C‐H‐Kopplungskonstanten von isotop substituierten Acetylacetonaten

Junge, Helmut; Musso, Hans; Záhorszky, U. I.

doi:10.1002/cber.19681010307

Cited by 17 publications

(7 citation statements)

References 13 publications

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“…Q-Sepharose and Sephacryl S-200 were purchased from Amersham Biosciences; dUTP, dUDP, and buffer materials were purchased from Sigma; phenol red indicator was purchased from Merck; Chelex resin (sodium form) was purchased from Bio-Rad; and vanadyl sulfate hydrate and VO(acac) 2 were purchased from Sigma-Aldrich. VO(d 7 -acac) 2 was synthesized from perdeuterated starting materials following the procedure described for the synthesis of 13 C-enriched VO(acac) 2 (21). All other materials were of analytical reagent grade; deionized distilled water was used throughout.…”

Section: Methodsmentioning

confidence: 99%

Catalytic and structural role of the metal ion in dUTP pyrophosphatase

Mustafi

Békési

Vértessy

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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The metal ion dependence of the catalytic activity of recombinant Escherichia coli dUTP pyrophosphatase (dUTPase), an essential enzyme preventing incorporation of uracil into DNA, has been investigated by steady-state kinetic, electron paramagnetic resonance, and electron nuclear double resonance methods. Values of k cat and kcat͞Km were 4.5 ؎ 0.1 s ؊1 and 0.49 ؎ 0.1 ؋ 10 6 M ؊1 ⅐s ؊1 in the absence of divalent metal ions, 14.7 ؎ 2.2 s ؊1 and 25.1 ؎ 7.4 ؋ 10 6 M ؊1 ⅐s ؊1 in the presence of Mg 2؉ or Mn 2؉ , and 24.2 ؎ 3.6 s ؊1 and 2.4 ؎ 0.7 ؋ 10 6 M ؊1 ⅐s ؊1 when supported by VO 2؉ or bis(acetylacetonato)oxovanadium(IV). Binding of VO 2؉ to the enzyme in the presence of dUDP, a nonhydrolyzable substrate analog, was specific and competitive with Mg 2؉ . Electron paramagnetic resonance spectra of the ternary enzyme-VO 2؉ -chelatedUDP complex revealed a pattern of 31 P superhyperfine coupling specifying two structurally equivalent phosphate groups equatorially coordinated to the VO 2؉ ion. Proton electron nuclear double resonance spectra revealed an equatorial acetylacetonate ligand, indicating that one of the organic ligands had been displaced. By molecular graphics modeling, we show that the diphosphate group of enzyme-bound dUDP is sterically accessible to a hemi-chelate form of VO 2؉ . We propose a similar location compatible with all kinetic and spectroscopic results to account for the reactivity of VO 2؉ and the VO 2؉ -chelate in dUTP hydrolysis. In this location the metal ion could promote an ordered conformation of the Cterminal fragment that is obligatory for catalysis but dynamically flexible in the free enzyme.C ontrary to ordinary expectation, the nucleic acid uracil can be incorporated into DNA in the cell because DNA polymerases do not distinguish between thymine and uracil. The most important cellular vehicle for hindering this process is the enzyme dUTP pyrophosphatase (dUTPase) (1, 2). This enzyme hydrolyzes dUTP into dUMP and pyrophosphate, thereby removing dUTP from the DNA biosynthetic pathway. Although several high to medium resolution x-ray studies of dUTPases from human (3), bacterial (4-6), and viral (7, 8) sources have been reported, there is no understanding of the structural basis of the catalytic mechanism. The C-terminal portion of each subunit of this trimeric enzyme is partly disordered in crystals and does not contribute to the electron density map. Furthermore, the binding site of Mg 2ϩ in the active site has not been identified. In the crystal structure of the equine infectious anemia virus (EIAV) enzyme, a Sr 2ϩ ion bound to both the ␣-and ␤-phosphate groups of dUDP has been localized (7), but in a position that would sterically prevent nucleophilic attack by a hydrolytic water molecule. Nonetheless, the catalytic importance of the C-terminal residues and the dependence of dUTPase action on Mg 2ϩ have been amply demonstrated by studies of the enzyme in solution (9-12). Because dUTPase has acquired increasing attention as a potential target enzyme in cancer and antiretroviral chemot...

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Section: Methodsmentioning

confidence: 99%

Catalytic and structural role of the metal ion in dUTP pyrophosphatase

Mustafi

Békési

Vértessy

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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“…It now seems interesting to use the method described here to examine many other ring systems to which a more or less aromatic character has been attributed on the basis of the chemical shift of their protons in the plane of the ring or other criteria; examples of such systems are phenylboron chelates (43)[69, ' ' I, metal complexes of glyoxal diimine (44), butadienyliron carbonyls (45)"' 'I, and many nitrogen, sulfur, and oxygen heterocycles, e. g. (46) and (47)" ' ' I.…”

Section: D~i T R O Z Z O [ '~~~mentioning

confidence: 99%

Bond Character of β‐Diketone Metal Chelates

Bock

Flatau

Junge

et al. 1971

Angew. Chem. Int. Ed. Engl.

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The vibrational spectra ofmolecules labeled with ' H , I3C, and l80 show that delocatization of double and single bonds in the six-membered ring is complete in all the metal chelates investigated of 2,4-pentanedione (acetylacetone), but not in 2,4-pentanedione itself: Mercury, on the other hand, is bonded to the central C atom of the ligands. The N M R spectra of the metal chelates of 3-mesityl-2,4-pentanedione and 3-anthryl-2,4-pentanedwne show that the chelate rings have no magnetic anisotropy comparable with that of benzene. A critical appraisal is made ofthe questions whether it is at all justifiable to attribute any "aromatic character" to such molecules and why all comparisons with the chemical reactivity of benzene have so far led to controversial conclusions concerning the character of the bonding in the metal chelates of 2,4-pentanedione.Angew. Chem. internat. Edit. / Vol. 10 (1971) / N o . 4 Received: December 18,1970 [A 811 IE] German version: Angew. Chem. 83,239 (1971) Translated by Express Translation Service, London [I] Benzenoid, nonbenzenoid, and antiaromatic systems, like homoaromatic and bicycloaromatic systems, are terms that are fixed by theory. (Aromaticity. Spec. Publ. Chem. SOC. London, No. 21, 1967.) Quasiaromatic and pseudoaromatic systems have been clearly defined by D. M. G. Lloyd and D. R. Marshall, Chem. Ind. (London) 1964,1760, but many chemists regard these as partly aromatic.[Z] J . A. Eluidge and L. M . Jackman, J. Chem. SOC. 1961, 859; J . A. Eluidge, Chem. Commun. 1965, 160: 2-pyridone 35%, furan 46%, pyrrole 59%, thiophene 75%.

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“…125°C; the 1 H NMR spectrum, which shows a multiplet at δ ϭ 7.43 ppm, is identical to that exhibited by the sample obtained by independent synthesis. [5] MS: m/z ϭ 266. The organic phase was worked up according to the usual procedure; the first product that eluted was 14 (26%), obtained as an orange oil that solidified when treated with hexane.…”

Section: Reaction Of 1e With Etonamentioning

confidence: 99%

“…13 C]-3-Chloroacetylacetone (8): SO 2 Cl 2 (1.6 g) was added dropwise to a solution of [1-13 C]acetylacetone [5] in CH 2 Cl 2 (8 mL) and then the reaction mixture was heated under reflux for 1 h. The solvent was evaporated under reduced pressure and the residue was then employed in the following reaction without any further purification.…”

Section: Preparation Of [1-mentioning

confidence: 99%

“…20%), which was converted into acetic anhydride by treatment with unlabeled acetyl chloride and then into acetylacetone (isotopic abundance ca. 10%) [5] by BF 3 -catalyzed reaction with unlabeled 2-propanone. Chlorination with sulfuryl chloride, followed by coupling with phenyldiazonium chloride in neutral solution gave [3-13 C]-1-chloro-1-phenylhydrazono-2-propanone (9) (isotopic abundance 4.5%) (Scheme 6).…”

Section: Introductionmentioning

confidence: 99%

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The Reactivity of (Z)‐5‐Acetyl‐3‐aryl‐2,3‐dihydro‐2‐[(thioacyl)methylene]1,3,4‐thiadiazoles: A Surprising Base‐Induced Conversion into 3‐(N‐arylamino)thiophenes

et al. 2003

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We report the reactivity shown by two classes of rarely investigated heterocycles, the 5-acetyl-2,3-dihydro-3-phenyl-2-(phenylmethylene)-1,3,4-thiadiazoles (6) and the 5-alkanoyl-3-aryl-2,3-dihydro-2-[(thioacyl)methylene]-1,3,4-thiadiazoles 1a−e. In both cases, strong bases promote cleavage of the thiadiazole ring with loss of thiocyanate anion, generating N-arylketeneimines and N-aryl(thioacyl)keteneimines 5, respectively. These very reactive species undergo either nucleophilic addition or [4+2] cycloaddition reactions involving the thioacyl function. The most surprising result

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Organische Metallkomplexe, III. Synthesen und C‐H‐Kopplungskonstanten von isotop substituierten Acetylacetonaten

Cited by 17 publications

References 13 publications

Catalytic and structural role of the metal ion in dUTP pyrophosphatase

Catalytic and structural role of the metal ion in dUTP pyrophosphatase

Bond Character of β‐Diketone Metal Chelates

The Reactivity of (Z)‐5‐Acetyl‐3‐aryl‐2,3‐dihydro‐2‐[(thioacyl)methylene]1,3,4‐thiadiazoles: A Surprising Base‐Induced Conversion into 3‐(N‐arylamino)thiophenes

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