Abstract: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 … Show more
“…A collection of single-residue 13 C-labeled hexasaccharides permitted to break the chemical shift degeneracy of the hexamer and experimentally assess some geometrical features of its conformation at the single residue level ( Delbianco et al, 2018 ). Still, a detailed description of the overall shape remained elusive, as “traditional” NMR parameters (i.e., NOEs, J-couplings) are limited to short-range distances ( Valverde et al, 2019b ; Krivdin, 2021 ) and cannot disclose the relative orientation of residues further apart in a linear saccharide chain ( Battistel et al, 2014 ).…”
The intrinsic flexibility of glycans complicates the study of their structures and dynamics, which are often important for their biological function. NMR has provided insights into the conformational, dynamic and recognition features of glycans, but suffers from severe chemical shift degeneracy. We employed labelled glycans to explore the conformational behaviour of a β(1-6)-Glc hexasaccharide model through residual dipolar couplings (RDCs). RDC delivered information on the relative orientation of specific residues along the glycan chain and provided experimental clues for the existence of certain geometries. The use of two different aligning media demonstrated the adaptability of flexible oligosaccharide structures to different environments.
“…A collection of single-residue 13 C-labeled hexasaccharides permitted to break the chemical shift degeneracy of the hexamer and experimentally assess some geometrical features of its conformation at the single residue level ( Delbianco et al, 2018 ). Still, a detailed description of the overall shape remained elusive, as “traditional” NMR parameters (i.e., NOEs, J-couplings) are limited to short-range distances ( Valverde et al, 2019b ; Krivdin, 2021 ) and cannot disclose the relative orientation of residues further apart in a linear saccharide chain ( Battistel et al, 2014 ).…”
The intrinsic flexibility of glycans complicates the study of their structures and dynamics, which are often important for their biological function. NMR has provided insights into the conformational, dynamic and recognition features of glycans, but suffers from severe chemical shift degeneracy. We employed labelled glycans to explore the conformational behaviour of a β(1-6)-Glc hexasaccharide model through residual dipolar couplings (RDCs). RDC delivered information on the relative orientation of specific residues along the glycan chain and provided experimental clues for the existence of certain geometries. The use of two different aligning media demonstrated the adaptability of flexible oligosaccharide structures to different environments.
“…F I G U R E 3 CBS-estimated RMS deviations of (a) carbon and (b) proton isotropic shieldings from the empirical values in methane as a function of the method number (given in the abscissa axis): VXSC (1), HCTH (2), HCTH97 (3), HCTH147 (4), THCTH (5), M06L (6), B97D (7), B3LYP (8), B3P86 (9), B3PW91 (10), B1B95 (11), MPW1PW91 (12), MPW1LYP (13), MPW1PBE (14), MPW3PBE (15), B98 (16), B971 (17), B972 (18), PBE1PBE (19), B1LYP (20), O3LYP (21), BhandH (22), BHandHLYP (23), BMK (24), M06 (25), M06HF (26), M062X (27), tHCTHhyb (28), HSEh1PBE (29), HSE2PBE (30), PBEh1PBE (31), wB97XD (32), wB97 (33), wB97X (34), TPSSh (35), X3LYP (36), LC-wPBE (37), CAM-B3LYP (38), WP04 (39), RHF (40), MP2 (41), KT1 (42), KT2 (43), KT3 (44), SOPPA (45), SOPPA (CCSD) (46), and CCSD(T) (47). Reproduced from Kupka, et al [88] with the permission of the American Chemical Society Much later, Kupka, et al [88] performed a systematic study of the performance of about four dozens of different DFT functionals together with five pure nonempirical methods, RHF, MP2, SOPPA, SOPPA (CCSD), and CCSD(T), for predicting 1 H and 13 C NMR chemical shifts of six small molecules, NH 3 , CH 4 , C 2 H 2 , C 2 H 4 , C 2 H 6 , and C 6 H 6 , with using Jensen's pcS-n (n = 1-4) basis set.…”
Section: Small Moleculesmentioning
confidence: 99%
“…Those seminal papers are discussed in full in the recent reviews. [ 35–38 ] Herewith, we will only illustrate the progress in this field with several most illustrative recent examples, documenting the application of computational NMR to this field. …”
Section: Computational 1h and 13c Nmr In Stereochemical Studies Of In...mentioning
confidence: 99%
“…Computation of NMR parameters provides a new guide in our understanding of the fundamental factors controlling stereochemistry and chemical reactivity of inorganic compounds, coordination complexes, organic and bioorganic molecules, [14][15][16][17][18][19][20][21][22][23][24][25][26] involving in particular natural products, [27][28][29][30][31][32][33][34] carbohydrates, [35][36][37][38] and carbonium ions. [39,40] Very recent results in this field appeared mainly in 2021 are outlined in the generalizing review by Kupka.…”
Present review outlines the advances and perspectives of computational 1H and 13C NMR applied to the stereochemical studies of inorganic, organic, and bioorganic compounds, involving in particular natural products, carbohydrates, and carbonium ions. The first part of the review briefly outlines theoretical background of the modern computational methods applied to the calculation of chemical shifts and spin–spin coupling constants at the DFT and the non‐empirical levels. The second part of the review deals with the achievements of the computational 1H and 13C NMR in the stereochemical investigation of a variety of inorganic, organic, and bioorganic compounds, providing in an abridged form the material partly discussed by the author in a series of parent reviews. Major attention is focused herewith on the publications of the recent years, which were not reviewed elsewhere.
“…Theoretical calculation of 13 C nuclear magnetic resonance (NMR) chemical shifts provides a powerful tool in structural elucidation of organic molecules, natural products, carbohydrates, and biochemical species. [1][2][3][4][5] Continuing our very recent survey of large natural products with multiple asymmetric centers, [6][7][8][9][10][11] current study is focused on the huge tetrakis monoterpene indole alkaloid, alasmontamine A, which is shown below in Figure 1.…”
H and 13 C nuclear magnetic resonance (NMR) chemical shifts of a tetrakis monoterpene indole alkaloid alasmontamine A with a molecular formula of C 84 H 91 N 8 O 12 have been calculated at the PBE0/pcSseg-2//pcseg-2 level of theory on M06-2X/aug-cc-pVDZ geometry. In the course of the preliminary conformational search, six true minimum energy conformers were identified that can contribute to the actual conformation of this huge alkaloid. Calculated chemical shifts generally demonstrated a good agreement with available experimental data characterized with a corrected mean absolute error of 0.10 ppm for the range of about 7 ppm for protons and 1.1 ppm for the range of about 160 ppm for carbons.
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