Tetrahedron p. 14123 - 14144 (1998)
Update date:2022-08-03
Topics:
Jimenez Blanco, Jose L.
Ortiz Mellet, Carmen
Fuentes, Jose
Garcia Fernandez, Jose M.
The reactivity and conformations in water solution of polyhydroxylated hexahydropyrimidine-2-thiones structurally related to biologically active nonulosonic acids and azaoctitols, obtained by intramolecular cyclization of sugar-derived μ-oxothioureas, have been investigated. The total preference for the axial orientation of the pseudoanomeric C - O bond and the high tendency to undergo acid-promoted intramolecular glycosylation are interpreted in terms of stabilizing hyperconjugative interactions in both the aminoketalic derivatives and the reactive azacarbenium cations. Moreover, repulsion between lone pairs and vicinal C - H bonds leads to a preference for structures bearing axial α-carbon substituents. The present results provide strong experimental evidence for the predominance of molecular orbital over electrostatic interactions in the stereoelectronic properties of these systems.
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Doi:10.1016/S0022-5347(05)67591-X
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