Fingerprints of molecular structure and hydrogen bonding effects in the /sup 13/C NMR spectra of monosaccharides with partially deuterated hydroxyls
A new NMR approach to structure elucidation of carbohydrates in solution is presented. Examined in detail are the isotopic multiplets in /sup 13/C NMR spectra that result from partial deuteration of the hydroxyls for a series of monosaccharides and some of their deoxy and methyl glycoside derivatives in Me/sub 2/SO-d/sub 6/ solutions. Chemical shift and isotope effect data are presented for the pyranose and furanose forms of aldopentoses, aldohexoses, and ketohexoses. The results show that the magnitude of the ..gamma.. effect resulting from deuteration of a hydroxyl on a vicinal carbon atoms is sensitive to the relative geometric relationship, cis or trans, of the hydroxyls in vicinal diol arrays. Thus, the multiplet pattern for carbons 3 and 4 of the pyranose ring can serve as a fingerprint of molecular structure at the pentopyranose level. The aldopentoses and ketohexoses are amenable to structural analysis by this simple approach. Ambiguity will arise for pairs of aldohexoses related to each other by epimerization at C5. Intramolecular hydrogen bonding between the hydroxyls at C2 and C4 in ..cap alpha..-D-talopyranose gives rise to some unusual effects. A mechanism involving isotopic perturbation of the equilibrium between the hydrogen-bonded structures O4-H...O2-H and O2-H...O4-H is suggested as the possible source of these effects. Similarly, the extra splitting observed in the /sup 13/C resonance of C3 of ..beta..-D-fucofuranose are rationalized in terms of an equilibrium between the hydrogen-bonded structures C5-O5-H...O3-H and Cl-O1-H...O3-H. The approach of isotopic multiplets appears to be uniquely suited for the study of such structures.
- Research Organization:
- Hercules Inc., Wilmington, DE
- OSTI ID:
- 5911826
- Journal Information:
- J. Am. Chem. Soc.; (United States), Vol. 106:21
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
DEUTERIUM
ISOTOPE EFFECTS
MONOSACCHARIDES
MOLECULAR STRUCTURE
CARBON 13
EXPERIMENTAL DATA
NMR SPECTRA
CARBOHYDRATES
CARBON ISOTOPES
DATA
EVEN-ODD NUCLEI
HYDROGEN ISOTOPES
INFORMATION
ISOTOPES
LIGHT NUCLEI
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
SACCHARIDES
SPECTRA
STABLE ISOTOPES
400302* - Organic Chemistry- Isotope Effects- (-1987)