New Synthetic Bromination Procedures for Use in Radiolabelling-Chemistry: Reaction of C-Metallated Derivatives of Carbohydrates with Bromide, in the Presence of Mild Oxidizing Agents
✍ Scribed by Jean-Richard Neeser; Laurance D. Hall; Julius A. Balatoni
- Publisher
- John Wiley and Sons
- Year
- 1983
- Tongue
- German
- Weight
- 660 KB
- Volume
- 66
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Abstract
In the presence of 2 mol‐equiv. of AcONa, both triglycosylborane 1 and dicyclohexylglycosylborane 2 readily react with bromine chloride generated in situ from bromide and N‐chlorosuccinimide (NCS) to give the bromo‐sugar 3 (75 and 60%, resp.). The use of the BH~3~‐THF/bromide/NCS/2 AcONa procedure permits the rapid, face‐specific synthesis of 6 (58% uptake of bromine) and face‐selective synthesis of 8/9 (71% uptake of bromine), from vinyl ether derivatives 5 and 7, respectively. The dicyclohexylborane/bromide/NCS/2 AcONa procedure leads to the fast and quantitative conversion of 11 to the bromosugar 12 (91%). Hydroboration‐transmetallation sequences give access to C‐mercuriated carbohydrates 13 (71%) and 14 (78%). The bis(glycosyl)mercury derivative 13 is spontaneously cleaved by reaction with one equivalent of bromide/chloramine‐T/aqueous HCl‐solution to give 3 (87%) and 14 (76%). Hydrostannylation of acetylenic sugar 15 gave the (E)‐stannylvinyl derivative 16 as the major product. This latter precursor 16 is spontaneously cleaved by the bromide/chloramine‐T/aqueous HCl‐solution reagent to give the bromovinyl‐sugar 17 (96%).