Publisher Summary This chapter provides an overview of the 13 Carbon-nuclear magnetic resonance ( 13 C-NMR) spectroscopy of monosaccharides. The 13 C-NMR spectroscopy has become increasingly important as a tool for the characterization and structural elucidation of sugars and their derivatives. Although 13 C-NMR is closely related to 1 H-NMR spectroscopy, especially when both types of spectra are recorded with Fourier-transform instruments, the two techniques are sufficiently different to be valuable complements to each other. In many cases, in particular when dealing with complex molecules such as polysaccharides, the amount of information obtainable from 1 H-NMR spectra is limited as compared to that revealed by 13 C- NMR spectra. This chapter provides an almost complete collection of 13 C- NMR chemical shifts of monosaccharides, their methyl glycosides, and acetates, along with the examples of shift data for as many different types of monosaccharide derivative as possible. It also provides details on sampling techniques and assignment techniques, and discusses the identity of monosaccharides, their structure determination, and conformational analysis .

Carbon-13 Nuclear Magnetic Resonance Spectroscopy of Monosaccharides

The effect of the relative orientation and electronegativity of substituents on the magnitude of 3J(aa), 3J(ae) and 3J(ee) is well predicated by a simple set of additivity constants, valid for pyranose rings in carbohydrates. The proposed set of parameters is used to calculate 327 coupling constants [3J(HH)] in a variety of pyranosides and related compounds. A comparison with experimental values taken from the literature shows that couplings in molecules which are conformationally pure and underformed can be predicted with a surprising accuracy. An overall root-mean-square agreement of 0.29 Hz is attained for a selected group of 305 coupling values. A statistical breakdown of ΔJ(aa) and ΔJ(ae) [ΔJ=J(exp)-J(calc)] along each carbon-carbon bond in the pyranose systems reveals an unexpected degree of geometrical homogeneity.

Prediction of anti and gauche vicinal proton‐proton coupling constants in carbohydrates: A simple additivity rule for pyranose rings

Carbon—hydrogen spin—spin coupling constants

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

Publisher Summary This chapter examines the carbon–proton coupling constants involved in the conformational analysis of sugar molecules. The indirect spin–spin coupling is independent of molecular rotation. The coupling mechanism is known to involve the electron spins of the bonding electrons and is the result of a weak electron polarization. A proton signal has two 13C satellites, each having an intensity that is 0.5% of that of the corresponding total proton resonance and located symmetrically around that resonance. In addition to providing information about 1H ( 1H couplings) these satellites allow the determination of the 1JC,H couplings with good resolution. With the advent of inverse detection and the corresponding gain in sensitivity, newer schemes for the measurement of long-range coupling constants have been proposed. They are based on the heteronuclear multiple-bond correlation derivative or variants of the heteronuclear multiple-quantum coherence experiment, and also on the heteronuclear single-quantum coherence experiment. The Hamiltonian gives the total electronic kinetic energy and the magnetic interactions between electron orbital motions and nuclear magnetic moments. It is found that two-bond carbon–proton coupling constants are much smaller than one-bond couplings and their signs can be negative or positive.

N.A. Matwiyoff

Papers

Dihedral-angle dependence of geminal, scalar, coupling-constants in [1-13C]-amino sugars