Towards the synthesis of a 2-deoxy-2-fluoro-d-mannose building block and characterisation of an unusual 2-S-phenyl anomeric pyridinium triflate salt via 1 → 2 S-migration.

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  • Additional Information
    • Source:
      Publisher: Elsevier Country of Publication: Netherlands NLM ID: 0043535 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1873-426X (Electronic) Linking ISSN: 00086215 NLM ISO Abbreviation: Carbohydr Res Subsets: MEDLINE
    • Publication Information:
      Publication: Amsterdam : Elsevier
      Original Publication: Amsterdam.
    • Subject Terms:
      Mannose*/chemistry ; Mannose*/chemical synthesis; Pyridinium Compounds/chemistry ; Pyridinium Compounds/chemical synthesis ; Mesylates/chemistry ; Models, Molecular ; Stereoisomerism ; Carbohydrate Conformation ; Salts/chemistry ; Salts/chemical synthesis
    • Abstract:
      Regio- and stereo-selective synthetic routes to 2-deoxy-2-fluoro-d-mannose building blocks are often experimentally challenging when using Selectfluor with the corresponding glycal. We targeted a late-stage method to introduce fluorine in a stereospecific manner using inversion via a triflate. Accordingly, synthesis of a conventionally protected 2-deoxy-2-fluoro-d-mannose β-thioglycoside donor, directly applicable to oligosaccharide synthesis, was attempted using C2-triflate inversion of the corresponding d-glucoside with TBAF. Unexpectedly, an anomeric pyridinium salt was isolated when attempting to form the C2-triflate using Tf 2 O in pyridine. Indicatively, this proceeds via a 1 → 2 S-migration delivering a 1,2-trans product with α-d-manno configuration and the anomeric pyridinium in a pseudo-equatorial position. The structure of this unexpected intermediate was confirmed in the solid-state using X-ray crystallography. Omission of the pyridine solvent led to dimer formation. Switching the aglycone to an O-para-methoxyphenyl enabled smooth C2 inversion to the desired 2-deoxy-2-fluoro d-mannose system, suitably equipped for further anomeric manipulation.
      Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
      (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)
    • Accession Number:
      PHA4727WTP (Mannose)
      0 (Pyridinium Compounds)
      0 (Mesylates)
      0 (Salts)
    • Publication Date:
      Date Created: 20240928 Date Completed: 20241116 Latest Revision: 20241116
    • Publication Date:
      20241118
    • Accession Number:
      10.1016/j.carres.2024.109275
    • Accession Number:
      39341003