The 1H and 13C NMR chemical shifts of Strychnos alkaloids revisited at the DFT level

Semenov, Valentin A.; Samultsev, Dmitry O.; Krivdin, Leonid B.

doi:10.1002/mrc.4948

Cited by 17 publications

(15 citation statements)

References 56 publications

(69 reference statements)

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“…Different LDBS schemes were systematically employed for the calculation of NMR parameters at the DFT and non-empirical levels of theory in a number of recent publications by Rusakov et al [ 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 ] and Semenov et al [ 80 , 81 , 82 , 83 , 84 , 85 ], as well as in numerous publications by different authors, which are not cited herewith in full in view of their multiplicity.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Computational NMR of Carbohydrates: Theoretical Background, Applications, and Perspectives

Krivdin

2021

Molecules

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This review is written amid a marked progress in the calculation of NMR parameters of carbohydrates substantiated by a vast amount of experimental data coming from several laboratories worldwide. By no means are we trying to cover in the present compilation a huge amount of all available data. The main idea of the present review was only to outline general trends and perspectives in this dynamically developing area on the background of a marked progress in theoretical and computational NMR. Presented material is arranged in three basic sections: (1)—a brief theoretical introduction; (2)—applications and perspectives in computational NMR of monosaccharides; and (3)—calculation of NMR chemical shifts and spin-spin coupling constants of di- and polysaccharides.

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Section: Theoretical Backgroundmentioning

confidence: 99%

Computational NMR of Carbohydrates: Theoretical Background, Applications, and Perspectives

Krivdin

2021

Molecules

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“…This combination was recently recommended for larger organic molecules. [15][16][17][18][19][20] In all nuclear shielding calculations, the gauge including atomic orbitals (GIAO) [21][22][23][24][25] formalism was used.…”

Section: Calculationsmentioning

confidence: 99%

Azo‐hydrazone molecular switches: Synthesis and NMR conformational investigation

Kurutos

Kamounah

Dobrikov

et al. 2021

Magnetic Reson in Chemistry

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A series of five intramolecularly hydrogen-bonded arylhydrazone (aryl = phenol, p-nitrophenol, anisole, quinoline) derived molecular switches have been synthesized and characterized by NMR and HRMS techniques. It was found that the compounds exist as different isomers in solution. An investigation of both conformational and/or configurational changes of the azo-hydrazone compounds was carried out by 1D 1 H-and 13 C-spectra, 2D NOESY, COSY, HSQC, and HMBC techniques. It was found that these stimuli-responsive molecular switches exist mainly in the E form by intramolecularly hydrogen bonded between NH and the pyridine nitrogen at equilibrium. Deprotonation of the neutral E form yields the E 0 deprotonated isomer. Prediction of 13 C-NMR chemical shifts was achieved by DFT quantum mechanical calculations. Anions have traditionally been difficult to calculate correctly, so calculations of the anion using different functionals, basis sets, and solvent effects are also included. Deuterium isotope effects on the 13 C-NMR chemical shifts were employed in the assignments and furthermore utilized as indicators of intramolecular hydrogen bonding. Studies in various organic solvents including CDCl 3 , CD 3 CN, and DMSO-d 6 were also performed aiming to monitor dynamic changes over several days. The effect of the hydrogen bonded solvents leads to Z forms.

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“…[75] Significant progress in the accuracy of DFT-based chemical shift prediction was accomplished during the 2010s. [76][77][78] For instance, Semenov et al [79] calculated 1 H and 13 C chemical shifts for 10 known strychnos alkaloids with a strychnine skeleton using DFT methods. It was found that calculated 1 H and 13 C NMR chemical shifts provided a distinctly good correlation with experiment, illustrated by a mean absolute error of 0.08 ppm in the range of 7 ppm for protons and 1.67 ppm in the range of 150 ppm for carbons.…”

Section: Nmr Chemical Shift Prediction: Synergy Between Empirical and Dft Approachesmentioning

confidence: 99%

Computer Assisted Structure Elucidation (CASE): Current and future perspectives

Elyashberg¹,

Argyropoulos²

2020

Magnetic Reson in Chemistry

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The first efforts for the development of methods for Computer-Assisted Structure Elucidation (CASE) were published more than 50 years ago. CASE expert systems based on one-dimensional (1D) and two-dimensional (2D) Nuclear Magnetic Resonance (NMR) data have matured considerably by now. The structures of a great number of complex natural products have been elucidated and/or revised using such programs. In this article, we discuss the most likely directions in which CASE will evolve. We act on the premise that a synergistic interaction exists between CASE, new NMR experiments, and methods of computational chemistry, which are continuously being improved. The new developments in NMR experiments (long-range correlation experiments, pure-shift methods, coupling constants measurement and prediction, residual dipolar couplings [RDCs]), and residual chemical shift anisotropies [RCSAs], evolution of density functional theory (DFT), and machine learning algorithms will have an influence on CASE systems and vice versa. This is true also for new techniques for chemical analysis (Atomic Force Microscopy [AFM], "crystalline sponge" X-ray analysis, and micro-Electron Diffraction [micro-ED]), which will be used in combination with expert systems. We foresee that CASE will be utilized widely and become a routine tool for NMR spectroscopists and analysts in academic and industrial laboratories. We believe that the "golden age" of CASE is still in the future.

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The ¹H and ¹³C NMR chemical shifts of Strychnos alkaloids revisited at the DFT level

Cited by 17 publications

References 56 publications

Computational NMR of Carbohydrates: Theoretical Background, Applications, and Perspectives

Computational NMR of Carbohydrates: Theoretical Background, Applications, and Perspectives

Azo‐hydrazone molecular switches: Synthesis and NMR conformational investigation

Computer Assisted Structure Elucidation (CASE): Current and future perspectives

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