ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The population of the conformations obtained by rotation around the C(2)—N and the N—C(O) bonds of AllNAc, GlcNAc, and GlcNMeAc derivatives was investigated by 1H-NMR spectroscopy. The AllNAc-derived α-D-and β-D-pyranosides 4-7, the AllNAc diazirine 16, and the GlcNAc-derived axial anomers α-D-8-10 prefer the (Z)-anti-conformation. A significant population of the (Z)-syn-conformer in the (Z)-syn/(Z)-anti-equilibrium for the equatorial anomers β-D-8-10 and the GlcNAc diazirine 17 was evidenced by an upfield shift of H—C(2), downfield shifts of H—C(1) and H—C(3), and by NOE measurements. The population of the (Z)-syn-conformation depends on the substituent at C(1) and is highest for the hexafluoroisopropyl glycoside. The population of the (Z)-syn-conformation of β-D-14 decreases with increasing polarity of the solvent, but a substantial population is still observed for solutions in D2O. Whereas the α-D-anomers of the hemiacetal 22 and the methyl glycoside 21 prefer the (Z)-anti-conformation in D2O solution, the corresponding β-D-anomers are mixtures of the (Z)-anti-and (Z)-syn-conformers. The diazirine 17 self-associates in CD2Cl2 solution at concentrations above 0.005M at low temperatures. The axial anomers of the GlcNMeAc derivatives α-D-26-28 are 2:1 to 3:1 mixtures of (Z)-anti-and (E)-anti-conformers, whereas the corresponding β-D-glycosides are ca. 1:3:6 mixtures of (Z)-syn-, (Z)-anti-, and (E)-anti-conformers.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19960790127
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