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.

Autor: Evans ST; Centre for Glycoscience and Lennard-Jones Laboratory, School of Chemical and Physical Sciences, Keele University, Keele, Staffordshire, ST5 5BG, UK., Tizzard GJ; UK National Crystallography Service, Chemistry and Chemical Engineering, University of Southampton, University Road, Southampton, SO17 1BJ, UK., Field RA; Department of Chemistry & Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK., Miller GJ; Centre for Glycoscience and Lennard-Jones Laboratory, School of Chemical and Physical Sciences, Keele University, Keele, Staffordshire, ST5 5BG, UK. Electronic address: g.j.miller@keele.ac.uk.
Jazyk: angličtina
Zdroj: Carbohydrate research [Carbohydr Res] 2024 Nov; Vol. 545, pp. 109275. Date of Electronic Publication: 2024 Sep 13.
DOI: 10.1016/j.carres.2024.109275
Abstrakt: 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.)
Databáze: MEDLINE
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