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

Since their first detection and bulk production, the fullerenes have
gained a primary role on the scientific scene, reaching their climax when
the 1996 Nobel Prize for Chemistry was awarded to Kroto, Curl and Smalley
for their seminal discovery. The unique physical and chemical properties
of these new forms of carbon led many scientists to predict several
technological applications. This created a heavy disappointment when it
was clear that fullerene-based materials would not soon be ready for the
market. However, the fullerenes have so far delighted several dozens of
researchers who found that C
 60
 and its relatives undergo a
variety of chemical reactions. In most cases, the new derivatives retain
the main properties of the original fullerene, and it is now not unlikely
that some functionalized fullerenes may find useful applications in the
field of materials science and technology. In this Article we summarize
the basic principles of the organic chemistry of fullerenes, together with
a description of the physicochemical properties that have made these
carbon cages popular in materials science, and review the most recent
achievements in the functionalization of fullerenes aimed at the
production of new molecular materials.

[60]Fullerene chemistry for materials science applications

Amongst the diversity of methods used by organisms to reduce damage caused by ultraviolet (UV) radiation, the synthesis of UV-screening compounds is almost ubiquitous. UV-screening compounds provide a passive method for the reduction of UV-induced damage and they are widely distributed across the microbial, plant and animal kingdoms. They share some common chemical features. It is likely that on early earth strong selection pressures existed for the evolution of UV-screening compounds. Many of these compounds probably had other physiological roles, later being selected for the efficacy of UV screening. The diversity in physiological functions is one of the complications in studying UV-screening compounds and determining the true ecological importance of their UV-screening role. As well as providing protection against ambient UV radiation, species with effective screening may also be at an advantage during natural ozone depletion events. In this review the characteristics of a wide diversity of UV-screening compounds are discussed and evolutionary questions are explored. As research into the range of UV-screening compounds represented in the biosphere continues, so it is likely that the properties of many more compounds will be elucidated. These compounds, as well as providing us with insights into natural responses to UV radiation, may also have implications for the development of artificial UV-screening methods to reduce human exposure to UV radiation.

Ultraviolet radiation screening compounds

Cascade Processes of Metallo Carbenoids

A quantitative theory of the isotropic electron‐nuclear spin interactions of carbon 13 in pi‐electron radicals is presented and applied to the hyperfine splittings observed in the electron spin resonance spectra of these substances. The splittings arise from sigma‐pi interactions which polarize both the 1s and 2s electrons. The 1s‐orbital spin polarization is shown to contribute a term of negative sign with a magnitude comparable to that from the 2s electrons. For an sp2 hybridized carbon atom that is bonded to three atoms, Xi (i=1, 2, 3), the hyperfine constant aC has the form aC=(SC+ ∑ i=13QCXiC)ρπ+ ∑ i=13QXiCCρiπ, where ρπ and ρiπ(i=1,2,3) are the pi‐electron spin densities on atoms C and Xi, respectively. The contribution of the 1s electrons is determined by SC and that of the 2s electrons by the Q's, where QBCA is the sigma‐pi parameter for the nucleus of atom A resulting from the interaction between the bond BC and the pi‐electron spin density on atom B. Calculations for a planar CHC2 fragment model...

THEORETICAL INTERPRETATION OF CARBON-13 HYPERFINE INTERACTIONS IN ELECTRON SPIN RESONANCE SPECTRA. Technical Note Report No. 9

The structures of sulfomycin I and berninamycin A

The structures of cervinomycins A1 (1) and A2 (2), a potent anti-anaerobic and anti-mycoplasmal antibiotic were investigated by means of recent NMR techniques of O-methyl ether (3) and C,O-dimethyl ether (4) obtained by methylation of 2 with CH3I in the presence of Ag2O. The antibiotic 2 posesses a polycyclic structure involving a xanthone skeleton. The structure of 1 was confirmed to be a hydroquinone of 2 from the evidences that oxidation of 1 with Ag2O and acetylation of 1 with (CH3CO)2O in pyridine afforded quantitatively 2 and triacetylcervinomycin A1 (7), respectively.

Structure of cervinomycin, a novel xantone antibiotic active against anaerobe and mycoplasma.

the carbon-carbon distance from that of graphite (case A) to that of benzene (case B) has very little effect on the calculated ionization potential (the difference is less than 1%) and only a moderate effect on the calculated optical transition energy. For both cases, the calculations predict that the lowest energy electronic transition should lie in the visible region of the spectrum; the absorption wavelength is found to be 492 nm for case A and 468 nm for case B. Thus, the DV-Xa calculations predict that the lowest electronic transition in the soccerball-shaped cluster C,, should lie a t an experimentally accessible energy. Measurement of this transition would provide valuable evidence as to whether or not the c6, species detected by Smalley and co-workers' is indeed shaped like a soccerball. The previous success of the DV-Xa method in the calculation of ionization potentials and optical excitations certainly suggests that its use as a predictive tool is warranted, and the results of experimental studies of the optical spectrum of c 6 0 are eagerly awaited.

Katsuhiko Kushida

Papers

The structures of sulfomycin I and berninamycin A

Structure of cervinomycin, a novel xantone antibiotic active against anaerobe and mycoplasma.

Structure of cervinomycin, a novel antianaerobic antibiotic.

Reactions of methoxycarbonylcarbene with ethers studied by 1H and 13C CIDNP

Synthesis and structure of nitrene-C60 adduct C60NPhth (Phth = Phthalimido)