title: Crystal structures of three bicyclic carbohydrate derivatives.
abstract: The title compounds, [(1R,3R,4R,5R,6S)-4,5-bis-(acet-yloxy)-7-oxo-2-oxabi-cyclo[4.2.0]octan-3-yl]methyl acetate, C14H18O8, (I), [(1S,4R,5S,6R)-5-acet-yloxy-7-hy-droxy-imino-2-oxobi-cyclo-[4.2.0]octan-4-yl acetate, C11H15NO6, (II), and [(3aR,5R,6R,7R,7aS)-6,7-bis-(acet-yloxy)-2-oxo-octa-hydro-pyrano[3,2-b]pyrrol-5-yl]methyl acetate, C14H19NO8, (III), are stable bicyclic carbohydrate derivatives. They can easily be synthesized in a few steps from commercially available glycals. As a result of the ring strain from the four-membered rings in (I) and (II), the conformations of the carbohydrates deviate strongly from the ideal chair form. Compound (II) occurs in the boat form. In the five-membered lactam (III), on the other hand, the carbohydrate adopts an almost ideal chair conformation. As a result of the distortion of the sugar rings, the configurations of the three bicyclic carbohydrate derivatives could not be determined from their NMR coupling constants. From our three crystal structure determinations, we were able to establish for the first time the absolute configurations of all new stereocenters of the carbohydrate rings.
authors.affiliation: Universität Potsdam, Institut für Chemie, Anorganische Chemie, Karl-Liebknecht-Strasse 24-25, D-14476 Potsdam, Germany.
authors.forename: Uwe
authors.initials: U
authors.lastname: Schilde
authors.affiliation: Universität Potsdam, Institut für Chemie, Anorganische Chemie, Karl-Liebknecht-Strasse 24-25, D-14476 Potsdam, Germany.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Kelling
authors.affiliation: Universität Potsdam, Institut für Chemie, Anorganische Chemie, Karl-Liebknecht-Strasse 24-25, D-14476 Potsdam, Germany.
authors.forename: Sumaira
authors.initials: S
authors.lastname: Umbreen
authors.affiliation: Universität Potsdam, Institut für Chemie, Anorganische Chemie, Karl-Liebknecht-Strasse 24-25, D-14476 Potsdam, Germany.
authors.forename: Torsten
authors.initials: T
authors.lastname: Linker
keywords: carbohydrate deriv­atives; configuration; conformation; crystal structure