Peptide Conformations. I. Nuclear Magnetic Resonance Study of the Carbamate Reaction of Amino Acids and Peptides

Lemieux, R. U.; Barton, Moira A.

doi:10.1139/v71-128

Cited by 30 publications

(15 citation statements)

References 21 publications

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“…It is known that the carbamate formation is very sensitive to steric hindrance originating in the amine structure. [12,13,18,[34][35][36][37][38][39][40]48,49] A primary amine in which the amino group is attached to a tertiary carbon atom has low tendency to form its carbamic acid. For example, a-Me-substituted alanine (1) does not form a detectable amount of carbamate because of a steric repulsion between the carbamate oxygen and a-Me.…”

Section: Dependence Of the Carbamate Formation And Decomposition On Cmentioning

confidence: 99%

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Kinetic investigation on carbamate formation from the reaction of carbon dioxide with amino acids in homogeneous aqueous solution

Yamamoto

Hasegawa

Ito

2011

J of Physical Organic Chem

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The kinetics of carbamate formation from the reaction of carbon dioxide with a-amino acids in D 2 O was first investigated by means of nuclear magnetic resonance spectroscopy. Potassium carbonate was used as the CO 2 source. For each amino acid, the maximum carbamate yield, the apparent rate constant for the carbamate formation k app , and the rate constants for the formation k 1 and the breakdown k À1 of the carbamate were estimated. Plots of log k 1 or log k À1 versus pK a of amino acids indicated that the formation rate k 1 increased with the basicity (pK a ) of amino acid, while the decomposition rate k À1 decreased. A Brfnsted b value of 0.39 was obtained from the former plot, being in good agreement with the previously reported ones (0.26-0.43). The observed negative pK a dependence of log k À1 (Brfnsted a = 0.34) is reasonable, because the carbamate decomposition is acid-catalyzed and the steady-state concentration of H + should be higher for weaker basic amines. The charge (s) and the lone-pair energy (E N ) at the nitrogen atom of the amino group were calculated. Although log k 1 correlated with s and E N , log k À1 was unrelated with both of these parameters. Considering that the carbamate formation (k 1 ) is not only base-catalyzed but should also be promoted by the nucleophilicity of the amino nitrogen, its correlation with s and E N in addition to pK a is rational. The irrelevance of log k À1 to s and E N is not surprising, because s and E N are not a direct measure of [H + ] of the solution.

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Section: Dependence Of the Carbamate Formation And Decomposition On Cmentioning

confidence: 99%

“…We used potassium carbonate K 2 CO 3 as the CO 2 source. [16][17][18][19][20] In principle, K 2 CO 3 generates CO 2 through the equilibrium reactions 3-5. It is known that most of carbonic acid exists as carbon dioxide in water, that is, [CO 2 ]/[H 2 CO 3 ] = 390.…”

Section: Introductionmentioning

confidence: 99%

Kinetic investigation on carbamate formation from the reaction of carbon dioxide with amino acids in homogeneous aqueous solution

Yamamoto

Hasegawa

Ito

2011

J of Physical Organic Chem

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“…The availability of 13 CO 2 and the development of high field NMR spectroscopy have provided effective tools to investigate carbamate formation in a wide range of applications [53,54].…”

Section: Other Biological Reactions Involving Comentioning

confidence: 99%

“…Lemieux and Barton [53] used this approach to describe the carbamic acid adducts formed with amino acids. The -amino groups of amino acids had a sufficiently low pKa to form carbamic acids at physiological pHs.…”

Section: Other Biological Reactions Involving Comentioning

confidence: 99%

Reaction of Primary and Secondary Amines to Form Carbamic Acid Glucuronides

Schaefer¹

2006

CDM

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Glucuronidation is an important mechanism used by mammalian systems to clear and eliminate both endogenous and foreign chemicals. Many functional groups are susceptible to conjugation with glucuronic acid, including hydroxyls, phenols, carboxyls, activated carbons, thiols, amines, and selenium. Primary and secondary amines can also react with carbon dioxide (CO(2)) via a reversible reaction to form a carbamic acid. The carbamic acid is also a substrate for glucuronidation and results in a stable carbamate glucuronide metabolite. The detection and characterization of these products has been facilitated greatly by the advent of soft ionization mass spectrometry techniques and high field NMR instrumentation. The formation of carbamate glucuronide metabolites has been described for numerous pharmaceuticals and they have been identified in all of the species commonly used in drug metabolism studies (rat, dog, mouse, rabbit, guinea pig, and human). There has been no obvious species specificity for their formation and no preference for 1 degrees or 2 degrees amines. Many biological reactions have also been described in the literature that involve the reaction of CO(2) with amino groups of biomolecules. For example, CO(2) generated from cellular respiration is expired in part through the reversible formation of a carbamate between CO(2) and the alpha-amino groups of the alpha- and beta-chains of hemoglobin. Also, carbamic acid products of several amines, such as beta-N-methylamino-L-alanine (BMAA), ethylenediamine, and L-cysteine have been implicated in toxicity. Studies suggested that a significant portion of amino-compounds in biological samples (that naturally contain CO(2)/bicarbonate) can be present as a carbamic acid.

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“…The following discussion is based on the From this assumption, justified on the grounds of n.m.r. results (11) (there is also other evidence (18, 19)), it follows that "mixed" dipeptides present a shorter end-toend distance with respect to the "pure" ones and, moreover, both the side chains lie on one side, and the charged groups on the other side of the molecule in the "mixed" dipeptides, whereas in the "pure" dipeptides in each side of the molecule we find a side chain and a charged group. Bearing in mind these structural features, we have interpreted the differences observed in the thermodynamic protonation data reported in Table 1.…”

Section: Resultsmentioning

confidence: 95%

Non‐covalent interactions in the protonation of diastereoisomeric dipeptides in aqueous solution

Calì

Cucinotta

Impellizzeri

et al. 1988

International Journal of Peptide and Protein Research

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New and already reported thermodynamic data concerning the protonation of a series of diastereoisomeric pairs of dipeptides have been compared with the upfield chemical shifts observed in the PMR spectra of some systems as a consequence of alkyl‐aryl interactions. The enthalpy and entropy changes associated with the protonation of the dipeptides, obtained by potentiometric and calorimetric measurements, together with the PMR data, show the importance of the solvophobic and the electrostatic interactions in the stereoselectivity of these systems. The overall agreement and the differences are discussed.

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Peptide Conformations. I. Nuclear Magnetic Resonance Study of the Carbamate Reaction of Amino Acids and Peptides

Cited by 30 publications

References 21 publications

Kinetic investigation on carbamate formation from the reaction of carbon dioxide with amino acids in homogeneous aqueous solution

Kinetic investigation on carbamate formation from the reaction of carbon dioxide with amino acids in homogeneous aqueous solution

Reaction of Primary and Secondary Amines to Form Carbamic Acid Glucuronides

Non‐covalent interactions in the protonation of diastereoisomeric dipeptides in aqueous solution

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