A PC program for calculation of dihedral angles from 1H NMR data

Cerda-Garcı́a-Rojas, Carlos M.; Zepeda, L. Gerardo; Joseph‐Nathan, Pedro

doi:10.1016/0898-5529(90)90113-m

Cited by 82 publications

(82 citation statements)

References 8 publications

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“…Together with the missing NOE between H3h and H-5h ( Figure 8) [3], this spatial arrangement indicates that the respective α-anomeric C-mannosyl hexopyranose is preferentially adopting a "C % conformation. This was substantiated by a comparison of the experimentally determined coupling constants of compound 1 with coupling constants estimated by applying a Karplus-type equation (see Table 3) [8,9]. Remarkably, model reactions of glucose, galactose and mannose yielded exclusively tryptophan-β-C-glycosyl derivatives with a %C " conformation.…”

Section: Figure 8 Section Of the One-dimensional Nmr Spectrum Of 2-(αmentioning

confidence: 81%

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Tryptophan glycoconjugates in food and human urine

Gutsche

Grun

Scheutzow

et al. 1999

Biochemical Journal

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Evaluating the formation of tryptophan glycoconjugates other than well-established Amadori rearrangement products, HPLCtandem MS (MS\MS) analysis of human urine collected from several healthy individuals proved the presence of one distinct tryptophan C-glycosyl compound [Horiuchi, Yonekawa, Iwahara, Kanno, Kurihara and Fujise (1994) J. Biochem. (Tokyo) 115, 362-366]. After isolation, unambiguous identification of this novel tryptophan metabolite as 2-(α-mannopyranosyl)--tryptophan was achieved by tandem MS combined with NMR spectroscopy including homonuclear COSY, heteronuclear multiple-bond connectivity and "H-detected heteronuclear multiple-quantum coherence experiments. Remarkably, a thorough evaluation of vicinal proton-proton coupling constants in different solvents and nuclear Overhauser effect experiments demonstrate the predominant axial orientation of the hydroxymethyl group of the hexopyranosyl residue. Likewise this spatial arrangement indicates that the respective α-anomeric C-mannosylhexopyranose is preferentially adopting a "C % con-

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Section: Figure 8 Section Of the One-dimensional Nmr Spectrum Of 2-(αmentioning

confidence: 81%

“…Solvents For establishing the conformation of compound 1 (Figure 1), vicinal coupling constants were estimated with an extended Karplus-type equation by the method of Haasnoot et al [8] with the PC program ALTONA [9], assuming standard dihedral angles of 60 m, 180 m and 300 m.…”

Section: Nmrmentioning

confidence: 99%

Tryptophan glycoconjugates in food and human urine

Gutsche

Grun

Scheutzow

et al. 1999

Biochemical Journal

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“…The DFT H-C-C-H dihedral angles derived from the three selected low-energy rotamers 1a, 1b and 1c, which indeed have slight variations, allowed us to calculate their theoretical vicinal coupling constants 3 J(H,H) by means of a generalized Karplus-type equation. 20,21 The values for the dihedral angles together with the corresponding coupling constants are listed in Table 2. The population-weighted average coupling constant for each H-C-C-H dihedral fragment, also included in Table 2, was calculated using the equation 3 …”

Section: Resultsmentioning

confidence: 99%

DFT and NMR parameterized conformation of valeranone

Torres-Valencia

Meléndez-Rodrı́guez

Álvarez-García

et al. 2004

Magnetic Reson in Chemistry

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A Monte Carlo random search using molecular mechanics, followed by geometry optimization of each minimum energy structure employing density functional theory (DFT) calculations at the B3LYP/6-31G* level and a Boltzmann analysis of the total energies, generated accurate molecular models which describe the conformational behavior of the antispasmodic bicyclic sesquiterpene valeranone (1). The theoretical H-C-C-H dihedral angles gave the corresponding 1H, 1H vicinal coupling constants using a generalized Karplus-type equation. In turn, the 3J(H,H) values were used as initial input data for the spectral simulation of 1, which after iteration provided an excellent correlation with the experimental 1H NMR spectrum. The calculated 3J(H,H) values closely predicted the experimental values, excepting the coupling constant between the axial hydrogen alpha to the carbonyl group and the equatorial hydrogen beta to the carbonyl group (J(2beta, 3beta)). The difference is explained in terms of the electron density distribution found in the highest occupied molecular orbital (HOMO) of 1. The simulated spectrum, together with 2D NMR experiments, allowed the total assignment of the 1H and 13C NMR spectra of 1.

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“…1). Furthermore, the use of a generalized Karplus type relationship (12) in the latter compounds allows us to establish a cis-type fusion of these derivatives, since the corresponding trans derivatives should exhibit coupling constants in the order of 7 Hz, while for compounds of type 2 one would expect 3~H H around 3-4 Hz. The structure of 3a has already been established (4) by single crystal X-ray analysis and those of 3b and 7 were determined in this work.…”

Section: Resultsmentioning

confidence: 99%

Fused heterocycles derived from pseudoephedrine and ephedrine

Farfán¹,

Santillán²,

Castillo³

et al. 1992

Can. J. Chem.

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). The formation of heterobicycles by condensation of (IR, 2R)-(-)-pseudoephedrine or (lR, 2s)-(-)-ephedrine with glyoxal is reported. In the case of pseudoephedrine, the nuclear magnetic resonance data of the crude reaction mixture indicate the presence of three isomeric compounds (5, 6, and 7), which were separated by fractional crystallization, while ephedrine afforded the oxazino-oxazine 8 and the known (5S*,6R*)-4,5-dimethyl-6-phenyl-1,4-oxazin-2-one (9). Conclusive spectroscopic evidence for the structures of the new compounds having the cis-[1,4]oxazino[3,2-b]-1,4-oxazine (5 and 8) and the 2,2'-bioxazolidine type structures (6 and 7) was obtained by measurement of the I3c satellite coupling constants in the 300 MHz 'H nmr spectra, combined with the evaluation of dihedral angles using a modified Karplus type relationship. Unequivocal 'H and I3c nmr spectral assignments for all new compounds were done using two-dimensional carbon-proton correlation experiments. Syntheses of the known 5a,6,1la,l2-tetrahydro[l,4]benzoxazino[3,2-blbenzoxazine (3a) whose crystal structure has been previously determined, as well as of its N,Nf-diisopropyl derivative 36, allowed us to corroborate the above observations for the six-membered ring heterocycles. Moreover, the structures of 36 and 7 were independently verified by single crystal X-ray diffraction studies, thus validating the structural conclusions deduced from nmr satellite multiplicity measurements.

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A PC program for calculation of dihedral angles from 1H NMR data

Cited by 82 publications

References 8 publications

Tryptophan glycoconjugates in food and human urine

Tryptophan glycoconjugates in food and human urine

DFT and NMR parameterized conformation of valeranone

Fused heterocycles derived from pseudoephedrine and ephedrine

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