PYRIDINIUM BETAINES OF 1,3-INDANDIONE SERIES

1959 ◽  
Vol 37 (5) ◽  
pp. 835-842 ◽  
Author(s):  
Gerassimos Frangatos ◽  
Alfred Taurins
Keyword(s):  
Negative Charge ◽  
Carbonyl Oxygen ◽  
Carboxylic Group ◽  
Pyridinecarboxylic Acids ◽  
Oxygen Atoms

2-Bromo- (II) and 2,2-dibromo-1,3-indandione (III) react with pyridine, 3- and 4-methylpyridine, and 2-, 3-, and 4-pyridinecarboxylic acids to give 1-(3-hydroxy-1-oxo-2-indenyl)-pyridinium hydroxide betaines. In the betaines derived from pyridinecarboxylic acids the negative charge is located not in the carboxylic group but on the carbonyl oxygen atoms.

119Sn, 13C and 1H NMR Spectra of Tris(1-butyl)stannyl D-Glucuronate

1997 ◽  
Vol 62 (8) ◽  
pp. 1169-1176 ◽  
Author(s):  
Antonín Lyčka ◽  
Jaroslav Holeček ◽  
David Micák
Keyword(s):  
Chemical Shift ◽  
Carbonyl Group ◽  
1H Nmr ◽  
Equatorial Plane ◽  
Title Compound ◽  
Nmr Spectra ◽  
Hydroxyl Groups ◽  
Carboxylic Group ◽  
H Nmr ◽  
Oxygen Atoms

The 119Sn, 13C and 1H NMR spectra of tris(1-butyl)stannyl D-glucuronate have been measured in hexadeuteriodimethyl sulfoxide, tetradeuteriomethanol and deuteriochloroform. The chemical shift values have been assigned unambiguously with the help of H,H-COSY, TOCSY, H,C-COSY and 1H-13C HMQC-RELAY. From the analysis of parameters of 119Sn, 13C and 1H NMR spectra of the title compound and their comparison with the corresponding spectra of tris(1-butyl)stannyl acetate and other carboxylates it follows that in solutions of non-coordinating solvents (deuteriochloroform) the title compound is present in the form of more or less isolated individual molecules with pseudotetrahedral environment around the central tin atom and with monodentately bound carboxylic group. The interaction of tin atom with oxygen atoms of carbonyl group and hydroxyl groups of the saccharide residue - if they are present at all - are very weak. In solutions in coordinating solvents (hexadeuteriodimethyl sulfoxide or tetradeuteriomethanol), the title compound forms complexes with one molecule of the solvent. Particles of these complexes have a shape of trigonal bipyramid with the 1-butyl substituents in equatorial plane and the oxygen atoms of monodentate carboxylic group and coordinating solvent in axial positions.

scholarly journals Spectral evidence for generic charge → acceptor interactions in carbamates and esters

RSC Advances ◽  
2020 ◽  
Vol 10 (20) ◽  
pp. 11871-11875
Author(s):  
Erode N. Prabhakaran ◽  
Shama Tumminakatti ◽  
Kamal Vats ◽  
Sudip Ghosh
Keyword(s):  
Negative Charge ◽  
Carbonyl Oxygen ◽  
Spectral Evidence ◽  
Ft Ir ◽  
Charge Stabilization

NMR, FT-IR spectral correlations of the R–O–CO groups in carbamates and esters of homologous alcohols (R) reveal R-group-dependent negative charge stabilization at the carbonyl oxygen and its donation to generic acceptors at Cα of even alkyl R.

Investigations of the biosynthesis of the phytotoxin coronatine

1994 ◽  
Vol 72 (1) ◽  
pp. 86-99 ◽  
Author(s):  
Ronald J. Parry ◽  
Sunil V. Mhaskar ◽  
Ming-Teh Lin ◽  
Alan E. Walker ◽  
Robson Mafoti
Keyword(s):  
Amino Acid ◽  
Pseudomonas Syringae ◽  
Cyclopropane Ring ◽  
Carbonyl Oxygen ◽  
Oxidative Cyclization ◽  
Amide Bond ◽  
Hydrogen Atoms ◽  
Coronafacic Acid ◽  
Polyketide Chain ◽  
Oxygen Atoms

The biosynthesis of the phytotoxin coronatine has been investigated by administration of isotopically labeled precursors to Pseudomonas syringae pv. glycinea. The structure of coronatine contains two moieties of distinct biosynthetic origin, a bicyclic, hydrindanone carboxylic acid (coronafacic acid) and a cyclopropyl α-amino acid (coronamic acid). Investigations of coronafacic acid biosynthesis have shown that this compound is a polyketide derived from three acetate units, one butyrate unit, and one pyruvate unit. The two carbonyl oxygen atoms of coronafacic acid were found to be derived from the oxygen atoms of acetate. Additional experiments are described that rule out some possible modes for assembly of the polyketide chain. Coronamic acid is shown to be derived from L-isoleucine via the intermediacy of L-alloisoleucine. Examination of the mechanism of the cyclization of L-alloisoleucine to coronamic acid revealed that the formation of the cyclopropane ring takes place with the removal of only two hydrogen atoms from the amino acid, one at C-2 and the other at C-6. The nitrogen atom at C-2 of L-alloisoleucine is shown to be retained. On the basis of these observations, a mechanism is postulated for the cyclization reaction that involves the diversion of an enzymatic hydroxylation reaction into an oxidative cyclization. Finally, a precursor incorporation experiment with deuterium-labeled coronamic acid demonstrated that free coronamic acid can be efficiently incorporated into coronatine. This observation indicates that the cyclization of L-alloisoleucine to coronamic acid can occur before formation of the amide bond between coronafacic acid and coronamic acid.

Bindung von Metall-Ionen an Dipeptide: Struktur von Thallium(I)-(3-benzyl-6-carboxylatomethyl-2,5-diketopiperazin) / Binding of Metal Ions by Dipeptides: Structure of Thallium(I) 3-Benzyl-6-carboxylatomethyl-2,5-diketopiperazine

1992 ◽  
Vol 47 (7) ◽  
pp. 952-956
Author(s):  
P. Mikulcik ◽  
P. Bissinger ◽  
J. Riede ◽  
H. Schmidbaur
Keyword(s):  
Solid State ◽  
Nitrogen Atom ◽  
Hydrogen Bonds ◽  
Diffraction Analysis ◽  
Carbonyl Oxygen ◽  
State Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Crystalline Product ◽  
Oxygen Atoms

Ester cleavage of aspartame (L-α-aspartyl-L-phenylalanine methylester) (1), by equimolar quantities of thallium ethoxide is accompanied by intramolecular cyclisation to give thallium 3-benzyl-6-(carboxylatomethyl)-2,5-dioxopiperazine (2). The solid state structure of the crystalline product was determined by single-crystal X-ray diffraction analysis. The cations were found to form four short and four elongated contacts to seven oxygen atoms and one nitrogen atom of a total of six neighbouring 3-benzyl-6-(carboxylatomethyl)-2,5-dioxopiperazine anions. There are inter-anionic hydrogen bonds only between the imino groups and the carbonyl oxygen atoms (O3, O4), featuring a pattern similar to that found for cytosine-guanosine contacts in DNA.

Ca2+Coordination to Backbone Carbonyl Oxygen Atoms in Calmodulin and Other EF-Hand Proteins: 15N Chemical Shifts as Probes for Monitoring Individual-Site Ca2+Coordination†

Biochemistry ◽  
1998 ◽  
Vol 37 (20) ◽  
pp. 7617-7629 ◽  
Author(s):  
Rodolfo R. Biekofsky ◽  
Stephen R. Martin ◽  
J. Peter Browne ◽  
Peter M. Bayley ◽  
James Feeney
Keyword(s):  
Chemical Shifts ◽  
Carbonyl Oxygen ◽  
Backbone Carbonyl ◽  
Individual Site ◽  
Ef Hand ◽  
Oxygen Atoms

scholarly journals 1H- and 13C-n.m.r. studies of the antitumour antibiotic luzopeptin. Resonance assignments, conformation and flexibility in solution

1988 ◽  
Vol 256 (1) ◽  
pp. 271-278 ◽  
Author(s):  
M S Searle ◽  
J G Hall ◽  
P G Wakelin
Keyword(s):  
Hydrogen Bonds ◽  
Nuclear Overhauser Effect ◽  
Resonance Assignments ◽  
Carbonyl Oxygen ◽  
Correlation Spectroscopy ◽  
Spin Lattice Relaxation ◽  
Double Quantum ◽  
Two Dimensional ◽  
Relaxation Data ◽  
Oxygen Atoms

The depsipeptide DNA-intercalating antibiotic luzopeptin was studied in solution by n.m.r. methods. Two-dimensional 1H double-quantum-filtered correlation spectroscopy (DQF-COSY) and nuclear-Overhauser-effect spectroscopy (NOESY) confirm the primary structure and twofold symmetry of luzopeptin and provide details of its three-dimensional conformation in solution. Trans-annular hydrogen bonds between the glycine NH groups and carbonyl oxygen atoms have been identified in the crystalline state [Arnold & Clardy (1981) J. Am. Chem. Soc. 103, 1243-1244], and are important in maintaining an antiparallel beta-sheet conformation. The n.m.r. data indicate that the glycine NH protons are appreciably shielded from the solvent molecules, which suggests that these hydrogen bonds are maintained in solution. The orientation of the quinoline chromophores is defined by two-dimensional NOE cross-peaks that position the N-methyl group of the L-beta-hydroxyvaline residue close in space to both the quinoline H-8 and serine NH proton. This pattern of NOEs is in accord both with the chromophore configuration found in the crystal and one where the quinoline rings are aligned in a parallel manner at right-angles to the depsipeptide ring. The n.m.r. data are consistent with a hydrogen bond between the quinoline hydroxy groups and the quinoline carbonyl oxygen atoms. The pyridazine acetylmethyl groups give NOEs to the C(alpha)H groups of the beta-hydroxy-N-methylvaline residues, showing that the acetyl groups, for at least some of the time, stretch over the depsipeptide ring, occluding one face of the molecule. Both of the latter features are also found in the crystal structure. Resonances in the 13C-n.m.r. spectrum of luzopeptin have been assigned by transferring 1H assignments to their covalently bonded carbon atoms via a heteronuclear shift-correlation experiment (HETCOR). The measurement of spin-lattice relaxation times and 1H-13C NOEs at specific sites in the molecule has led us to conclude that segmental motions within the depsipeptide ring are restricted and that the 13C relaxation data for luzopeptin's protonated carbon atoms are adequately described by isotropic tumbling in solution. Furthermore, relaxation data for the carbon atoms of the quinoline chromophores show that these rings exhibit similar motion to the depsipeptide ring and are not rotating rapidly with respect to it. Taken together all the data imply that luzopeptin is fairly rigid in solution, on the time scale of molecular tumbling, and has, or can readily attain, a staple-like structure suitable for bisintercalation.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Heme-Dependent Rubber Oxygenase RoxA of Xanthomonas sp. Cleaves the Carbon Backbone of Poly(cis-1,4-Isoprene) by a Dioxygenase Mechanism

2005 ◽  
Vol 71 (5) ◽  
pp. 2473-2478 ◽  
Author(s):  
Reinhard Braaz ◽  
Wolfgang Armbruster ◽  
Dieter Jendrossek
Keyword(s):  
Alcohol Dehydrogenase ◽  
Isotope Exchange ◽  
Carbonyl Oxygen ◽  
Cleavage Product ◽  
Enzymatic Cleavage ◽  
Cleavage Reaction ◽  
Carbon Backbone ◽  
Enzymatic Reduction ◽  
Oxygen Atoms

ABSTRACT Oxidative cleavage of poly(cis-1,4-isoprene) by rubber oxygenase RoxA purified from Xanthomonas sp. was investigated in the presence of different combinations of 16O2, 18O2, H2 16O, and H2 18O. 12-Oxo-4,8-dimethyl-trideca-4,8-diene-1-al (ODTD; m/z 236) was the main cleavage product in the absence of 18O-compounds. Incorporation of one 18O atom in ODTD was found if the cleavage reaction was performed in the presence of 18O2 and H2 16O. Incubation of poly(cis-1,4-isoprene) (with RoxA) or of isolated unlabeled ODTD (without RoxA) with H2 18O in the presence of 16O2 indicated that the carbonyl oxygen atoms of ODTD significantly exchanged with oxygen atoms derived from water. The isotope exchange was avoided by simultaneous enzymatic reduction of both carbonyl functions of ODTD to the corresponding dialcohol (12-hydroxy-4,8-dimethyl-trideca-4,8-diene-1-ol (HDTD; m/z 240) during RoxA-mediated in vitro cleavage of poly(cis-1,4-isoprene). In the presence of 18O2, H2 16O, and alcohol dehydrogenase/NADH, incorporation of two atoms of 18O into the reduced metabolite HDTD was found (m/z 244), revealing that RoxA cleaves rubber by a dioxygenase mechanism. Based on the labeling results and the presence of two hemes in RoxA, a model of the enzymatic cleavage mechanism of poly(cis-1,4-isoprene) is proposed.

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