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Updated: Jun 20, 2026

Facile Preparation of (2Z,4E)-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate
Published on: June 21, 2017
E versus Z geometry in beta-D-arabino-hexopyranosidulose oximes
Matthias Lergenmüller1, Ulrich Kläres, Frieder W Lichtenthaler
1Clemes-Schöpf-Institut für Organische Chemie und Biochemie, Technische Universität Darmstadt, Petersenstrasse 22, D-64287 Darmstadt, Germany.
Abstract:
Koenigs-Knorr-type glycosidations of peracylated 2Z-benzoyloxyimino-glycopyranosyl bromides invariably proceed with retention of the Z-geometry. Accordingly, the many beta-D-hexosidulose oximes in literature which were prepared in this way and for which the oxime geometry has not been addressed explicitly, are the Z-oximes throughout. By contrast, oximation of beta-D-hexopyranosid-2-uloses leads to mixtures of E and Z oximes readily separable and structurally verifiable by (1)H and (13)C NMR. Configurational assignments rested on comparative evaluation of NMR data of E and Z isomers, and, most notably on an X-ray structural analysis of the pivaloylated isopropyl 2E-benzoyloxyimino-2-deoxy-beta-D-arabino-hexopyranoside revealing the unusual (1)S(5)<==>(1,4)B conformation for the pyranoid ring.
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