Reversal of Stereoselectivity in Cycloadditions of Five-Membered Cyclic Nitrones Derived from Hexoses

• Autoři: MALATINSKY T.; SPISAKOVA M.; BABJAK M.; DOHANOSOVA J.; MAREK Jaromír; MONCOL J.; FISCHER R.
• Rok publikování: 2017
• Druh: Článek v odborném periodiku
• Časopis / Zdroj: European Journal of Organic Chemistry
• Fakulta / Pracoviště MU: Středoevropský technologický institut
• www: https://onlinelibrary.wiley.com/doi/epdf/10.1002/ejoc.201601488
• Doi: http://dx.doi.org/10.1002/ejoc.201601488
• Klíčová slova: Heterocycles; Nitrones; Carbohydrates; Cycloaddition; Diastereoselectivity
• Popis: Two five-membered cyclic nitrones derived from hexoses, a newly synthesized D-allo-configured nitrone and an already known D-talo-configured nitrone, have been examined in 1,3-dipolar cycloaddition reactions with vinyl acetate, allyl benzoate, methyl acrylate, acrylonitrile, and vinylene carbonate. The reactions of the D-allo-configured nitrone proceeded preferentially through the expected exo-anti transition state, but all the cycloadditions of the D-talo-configured nitrone surprisingly showed high exo-syn selectivity. This reversal of stereoselectivity has been explained by 3D analysis of the preferred conformations of the nitrones, obtained from X-ray data. The structures were further inspected using CONFLEX, PM5, and DFT calculations. All these methods revealed that the dioxolane substituents attached to C-5 of both nitrones had opposite spatial locations.

Související projekty

• Czech Infrastructure for Integrative Structural Biology