Publisher Summary This chapter deals with the use of nuclear magnetic resonance (NMR) spectroscopy in the study of mono– and oligosaccharides. The importance of NMR spectroscopy in the study of carbohydrates has increased tremendously. This has occurred primarily because the introduction of pulsed Fourier transform (FT) NMR spectrometers has made the measurement of I3 C NMR spectral parameters easy, which is particularly important for the study of carbohydrates in aqueous solutions. In addition, pulsed NMR instruments have increased the sensitivity of 'H NMR spectra by several orders of magnitude and facilitated the measurement of relaxation times and nuclear Overhauser enhancement (NOE) factors. The chapter discusses the way to assign NMR parameters and the way to use these values in the study of carbohydrates. Moreover, the chapter illustrates that the assignment of the NMR signals is a prerequisite for the application of NMR spectroscopy in structural investigations of carbohydrates. Because assignment techniques have been described in many reviews and monographs, special emphasis is given to the problems associated with the assignment of signals in the NMR spectra of carbohydrates and their derivatives.

Nuclear magnetic resonance spectroscopy in the study of mono‐ and oligosaccharides

Conformational studies on aldonolactones by n.m.r. spectroscopy. Conformations of d-glucono-1,5-lactone and d-mannono-1,5-lactone in solution

Die Abramov-Reaktion von 2,3:5,6-Di-O-isopropyliden-α-D-mannofuranose (1) mit Dimethylphosphit fuhrt unter innerer Umesterung zum blockierten 1,2λ5-Oxaphosphorinan 2. Die Rontgenstrukturanalyse des Tosylats 3 ergibt zwei symmetrieunabhangige Molekule A und B in der Elementarzelle. Die Tosyloxygruppe nimmt in beiden Molekulen unterschiedliche Stellungen zum Heterosechsring ein. Der Ring in A liegt in einer fast idealen Bootkonformation B1,4(D) vor, der Ring in B ist in Richtung auf eine Twistbootkonformation 2S4(D) verdreht. Der Phosphorylsauerstoff steht axial, die Phosphonomethylgruppe aquatorial. 1H-NMR-Spektren bei 270 MHz fuhren zur Aufklarung aller Kopplungsparameter. Die Konformation in Losung entspricht einer leicht verdrillten Bootkonformation.



Phosphorus-containing Carbohydrates, XVI. Ring Expansion of Furanose Rings to 1,2λ5-Oxaphosphorinanes



The Abramov reaction of 2,3:5,6-diO-isopropylidene-α-D-mannofuranose (1) with dimethyl phosphite yields the blocked 1,2λ5-oxaphosphorinane 2 by intramolecular transesterification. The X-ray analysis of the tosylate 3 gives evidence of two types of symmetry independent molecules, A and B, in the unit cell. These differ in the relative position of the tosyloxy group and the hetero six-membered ring. The latter adopts a nearly ideal boat conformation B1,4(D) in A, and is twisted towards a scew conformation 2S4(D) in B. The phosphoryl oxygen is found in axial, the phosphono-methyl group in equatorial position. 1H NMR spectra at 270 MHz allow a complete assignment of all couplings. The conformation in solution is consistent with a slightly distorted boat conformation.

Phosphorhaltige Kohlenhydrate, XVI. Ringerweiterung von Furanose-Ringen zu 1,2λ5-Oxaphosphorinanen

In order to synthesize meso- and (2 R ,4 R )-2,4-diaminoglutaric acids, a synthetic route has been developed starting from Garner's aldehyde and where the key steps are the asymmetric hydrogenations of ( E )- and ( Z )-( R )-3- tert -butoxycarbonyl-2,2-dimethyl-4-[2′-(benzamido)-2′-(methoxycarbonyl)ethenyl]-1,3-oxazolidine, under heterogeneous conditions, followed by oxidation and further hydrolysis A model is proposed to explain the stereochemical outcome of the asymmetric hydrogenation

Asymmetric synthesis of meso- and (2R,4R)-2,4-diaminoglutaric acids

Aus den Daten einer vollstandigen Analyse der 1H-NMR-Spektren der C6-Cycloolefine ergeben sich nach der Karplus-Relation und der R-Wert-Methode Torsionswinkel, die fur Cyclohexen (2) eine Halbsessel-Konformation, fur 1,3-Cyclohexadien (3) eine nicht planare und fur 1,4-Cyclohexadien (4) eine planare oder nahezu planare Konformation anzeigen. Die Diskussion dieser Ergebnisse erfolgt auf der Basis von Deformationen der CCC-Bindungs- und -Torsionswinkel, die durch Spannungskrafte hervorgerufen werden.



1H-Nuclear Magnetic Resonance Investigations of C6-Cycloolefins



The 1H NMR spectra of the C6-cycloolefins were completely analysed. In connection with the Karplus-relation and the R-value method the resulting data yielded torsional angles which show a half-chair conformation for cyclohexene (2), for 1,3-cyclohexadiene (3) a not quite planar, and for 1,4-cyclohexadiene (4) a planar or nearly planar conformation. These results were discussed in terms of deformations of CCC-bond angles and torsional angles caused by strain forces.

1H-Kernresonanz-spektroskopische Untersuchungen an C6-Cycloolefinen

Conformationally rigid systems such as xylopyranose 1,2,4-ortho esters (1a) and (1b) and 10-methoxy-6-aza-isoadamantane (2), for which the identity of conformations both in the crystalline state and in solution can reasonably be assumed, provide good models for the study of experimental correlations between the spin–spin coupling constants (J) of the vicinal protons and the dihedral bond angles (DBA) determined from an X-ray study in the HCCH bond system. The Karplus equations and their modifications (with and without corrections for the electronegativity of adjacent groups) were found to be unable to provide satisfactory correlations between these parameters. Optimum coefficients for the equations connecting the J and DBA values with corrections for electronegativity were calculated by the least squares method. The same procedure was used to obtain an equation connecting the J with DBA values using the sum of the chemical shifts as a measure of the electronic factors affecting the J ∝ DBA dependence. The accuracy of the equation thus obtained lies within ±18% as opposed to ±48% for the original Karplus equations. A similar correlation was obtained for the angles between the intercrossing lines formed by the directions of the vicinal CH bonds (ILA). When combined with the sum of chemical shifts, ILA provides a better correlation with the coupling constants J than the conventional parameter DBA.

Correlations between molecular parameters and the spin–spin coupling constants of vicinal protons: Criticism of the karplus equations

The dihedral and bond direction angles between all pairs of vicinal protons of the arabinofuranose residue were calculated from the coordinatees of the hydrogen atoms found by an X-ray study of 3-O-acetyl-β-L-arabinofuranose 1,2,5-orthobenzoate. The values found were compared with those calculated with the help of correlation equations previously proposed by Karplus and recently by the authors, linking the values of those angles with the spin-spin coupling constants of vicinal protons [3J(H,H′)]. It has been found that the best agreement between the angles found crystallographically and calculated from the 1H NMR data can be achieved using the equation which includes bond direction angles and the sum of the chemical shifts of the protons involved.

Verification of the correlation between geometric parameters of molecules and the parameters of their 1H NMR spectra

An earlier paper by the authors has undergone criticism by Jankowski and Rabczenko. The arguments presented are analysed in this paper and the criticism is rejected.

L. G. Vorontsova

Papers

Correlations between molecular parameters and the spin–spin coupling constants of vicinal protons: Criticism of the karplus equations

Verification of the correlation between geometric parameters of molecules and the parameters of their 1H NMR spectra

Comments on the correlations between geometric parameters of molecules and parameters of their 1H NMR spectra: The answer to a criticism