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Pivaloylated Glucoconjugates with Heterocyclic Oximes

Condensation of tetra-O-pivaloyl-alpha-D-glucopyranosyl bromide (1) with three heterocyclic oximes: 3-hydroxyiminoquinuclidine (2), 4-hydroxyiminomethylpyridine (3) and N-methyl-2-hydroxyiminomethylimidazole (4) leads to the beta-N-glucoconjugates. Conjugates 6 and 7 were synthesized using aromatic compounds 3 and 4 as the starting material. They were obtained in two isomeric forms (E and Z) due to the restricted rotation around the oxime`s double bond. The presence of E and Z isomers was proved by comparison of NMR spectra with calculated GIAO/DFT NMR spectra on B3LYP/6-31G(d) level of theory and by X-ray structural analysis of starting oxime reagents. Isomery was not observed in the quinuclidinium glucoconjugate 5.

Conjugation; Heterocycles; N-glucoconjugates; X-ray structure; DFT calculations

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