PREPARATION OF RACEMIC 2r‐CARBOXY‐TRANS, TRANS‐3, 4‐DIDEUTERO‐PYRROLIDINE (DL‐TRANS, TRANS‐3, 4‐DIDEUTERO‐PROLINE) AND UNAMBIGUOUS ASSIGNMENT OF PROTONS IN THE 1H N.M.R. SPECTRUM OF PROLINE

Anteunis, M.; Borremans, Frans; Becu, Chr.; Sleeckx, Jef

doi:10.1111/j.1399-3011.1979.tb01955.x

Cited by 8 publications

(4 citation statements)

References 17 publications

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“…Proton NMR Spectral Analysis . The published NMR data for l -proline in water reveal some inconsistencies in the reported J -couplings, especially in the values of the vicinal 3 J -couplings. ,2b, The reason for such inconsistency is the complexity of the spectrum characteristic for a strongly coupled spin system 10a. None of the previous analyses are complete, as no iterative fittings to experimental spectra, either by LAOCN3 10b or full line shape 10c,d calculations, were reported. 2b, These incomplete analyses of strongly coupled 1 H spectra were likely to lead to inaccurate J -couplings, as confirmed by our results presented below.…”

Section: Resultsmentioning

confidence: 99%

“…d Values reported at pD = 7.4. The spectral parameters were determined by eye comparison of the experimental (250 MHz) and the calculated spectra 2b…”

Section: Resultsmentioning

confidence: 99%

“… a For comparison, 3 J HH couplings reported in refs and b are also included (see also Supporting Information, Figures S1 and S2). b 20 mM solution, pD = 8.1 ± 0.2. c 320 mM solution, pD = 7.6 ± 0.2.…”

Section: Resultsmentioning

confidence: 99%

“…The best part of the literature on experimental and computational studies of l -proline and related derivatives relies on the conformational geometries and populations derived by Haasnoot et al They employed least-squares fittings of 3 J -couplings using a simple two-site equilibrium model between C γ -endo and C γ -exo conformers (Figure ) and Karplus-type equations . However, the experimental values of 3 J -couplings used in their fittings were derived from incomplete spectral analysis and are significantly different from those obtained by us from full line shape analysis (Table ). Thus, the reliability of the results for l -proline can be questioned.…”

Section: Resultsmentioning

confidence: 99%

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Conformational Analysis of l-Prolines in Water

Aliev

Courtier‐Murias

2007

J. Phys. Chem. B

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The results of the ring conformational analysis of L-proline, N-acetyl-L-proline, and trans-4-hydroxy-L-proline by NMR combined with calculations using density functional theory (DFT) and molecular dynamics (MD) are reported. Accurate values of 1H-1H J-couplings in water and other solvents have been determined. Using a two-site equilibrium model, the Cgamma-endo conformer of L-proline in water has been identified as intermediate between gammaTdelta [twist(Cgamma-endo, Cdelta-exo)] and gammaE [envelope(Cgamma-endo)] and the Cgamma-exo conformer as betaTgamma. Both conformers were equally populated at room temperature. The N-acetyl [cis-rotamer gammaTbeta(80%)/gammaE(20%) and trans-rotamer gammaTbeta(61%)/gammaE(39%)] and 4-hydroxy (gammaEpsilon) derivatives showed significant changes in both the population and the geometries of the preferred ring conformers. The combination of NMR predicted populations with the DFT B3LYP/6-311+G(2d,p)/IEFPCM calculations proved successful, resulting in fairly accurate predictions of J-couplings. Simulations using MD were mostly in favor of the two-site equilibrium model between Cgamma-endo and Cgamma-exo conformers, similar to that used for the analysis of NMR J-couplings. Various force fields examined for MD simulations failed to reproduce the ring conformational geometries and populations of L-proline in water accurately, while significantly better agreement with NMR was found for trans-N-acetyl-L-proline using GROMOS and AMBER force fields.

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Section: Resultsmentioning

confidence: 99%

“…d Values reported at pD = 7.4. The spectral parameters were determined by eye comparison of the experimental (250 MHz) and the calculated spectra 2b…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Conformational Analysis of l-Prolines in Water

Aliev

Courtier‐Murias

2007

J. Phys. Chem. B

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Total Lineshape Analysis of High-Resolution NMR Spectra by Simulated Annealing

Чертков

Cheshkov

Синицын

2017

eMagRes

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Relationship between proton–proton nmr coupling constants and substituent electronegativities. III. Conformational analysis of proline rings in solution using a generalized Karplus equation

Haasnoot¹,

Leeuw²,

Leeuw³

et al. 1981

Biopolymers

134

107

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SynopsisThe relationship between published vicinal proton-proton coupling constants and the pseudorotation properties of the pyrrolidine ring in L-proline, 4-hydroxy-~-proline, 4-fluoro-L-proline, and several linear and cyclic model proline peptides is investigated. Compared to earlier studies, several important improvements are incorporated (1) a new empirical generalization of the classical Karplus equation is utilized, which allows a valid correction for the effects of electronegativity and orientation of substituents on 35HH; (2) an empirical correlation between proton-proton torsion angles and the pseudorotational parameters P and T, is derived; and (3) the best fit of the conformational parameters to the experimental coupling constants is obtained by means of a computerized iterative least-squares procedure. Two pseudorotation ranges were considered, classified as type N ( x 2 positive sign) and type S (XZ negative sign). The conformational equilibrium is fully described in terms of four geometrical parameters (PN, TN, Ps, 7s) and the equilibrium constant K . The present results indicate that, in general, the geometrical properties found in x-ray studies of proline and hydroxyproline residues are well preserved in solution. Several novel features are encountered, however. It is demonstrated that the proline ring occurs in a practically 1:l conformational equilibrium between well-defined N-and S-type forms. Introduction of an amide group at the C-terminal end has no observable effect on this equilibrium, but the formation of a peptide bond a t the imino nitrogen site results in a pronounced, but not exclusive, preference for an S-type form which is roughly 1.1 kcal/mol more stable than its N-type counterpart. The hydroxyproline ring system in neutral or acidic medium displays a pure N-type state, but N-acetylation results in the appearance of a minor (S-type) conformation. Cyclic proline dipeptides similarly exist in a biased conformational equilibrium. The major form (77-88%) corresponds to the N-type conformer observed in the solid state; the minor S-form has not been observed before. In contrast, cyclic hydroxyproline dipeptides display complete conformational purity. Ranges of endocyclic torsion angles deduced for the various classes of pyrrolidine derivatives in solution are presented. Each torsion appears confined to a surprisingly narrow range, comprising about 4'-8" in most cases. In all, the proline ring is far less "floppy" than hitherto assumed.

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PREPARATION OF RACEMIC 2r‐CARBOXY‐TRANS, TRANS‐3, 4‐DIDEUTERO‐PYRROLIDINE (DL‐TRANS, TRANS‐3, 4‐DIDEUTERO‐PROLINE) AND UNAMBIGUOUS ASSIGNMENT OF PROTONS IN THE 1H N.M.R. SPECTRUM OF PROLINE

Cited by 8 publications

References 17 publications

Conformational Analysis of l-Prolines in Water

Conformational Analysis of l-Prolines in Water

Total Lineshape Analysis of High-Resolution NMR Spectra by Simulated Annealing

Relationship between proton–proton nmr coupling constants and substituent electronegativities. III. Conformational analysis of proline rings in solution using a generalized Karplus equation

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