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Synthesis of a Muscarinic Receptor Antagonist via a Diastereoselective Michael Reaction, Selective Deoxyfluorination and Aromatic Metal−Halogen Exchange Reaction
- Source :
- The Journal of Organic Chemistry. 66:6775-6786
- Publication Year :
- 2001
- Publisher :
- American Chemical Society (ACS), 2001.
-
Abstract
- An efficient synthesis of a structurally unique, novel M(3) antagonist 1 is described. Compound 1 is conveniently disconnected retrosynthetically at the amide bond to reveal the acid portion 2 and the amine fragment 3. The synthesis of key intermediate 2 is highlighted by a ZnCl(2)-MAEP complex 19 catalyzed diastereoselective Michael reaction of dioxolane 7 with 2-cyclopenten-1-one (5) to establish the contiguous quaternary-tertiary chiral centers and a subsequent geminal difluorination of ketone 17 using Deoxofluor in the presence of catalytic BF(3).OEt(2). The synthesis of the amine moiety 3 is highlighted by the discovery of a novel n-Bu(3)MgLi magnesium-halogen exchange reaction for selective functionalization of 2,6-dibromopyridine. This new and practical metalation protocol obviated cryogenic conditions and upon quenching with DMF gave 6-bromo-2-formylpyridine (26) in excellent yield. Further transformations afforded the amine fragment 3 via reductive amination with 35, Pd-catalyzed aromatic amination, and deprotection. Finally, the highly convergent synthesis of 1 was accomplished by coupling of the two fragments. This synthesis has been used to prepare multi-kilogram quantities of the bulk drug.
- Subjects :
- Receptor, Muscarinic M3
chemistry.chemical_classification
Ketone
Hydrocarbons, Fluorinated
Chemistry
Stereochemistry
Metalation
Organic Chemistry
Stereoisomerism
Muscarinic Antagonists
Amides
Receptors, Muscarinic
Combinatorial chemistry
Reductive amination
chemistry.chemical_compound
Dioxolane
Michael reaction
Animals
Humans
Moiety
Amine gas treating
Amination
Subjects
Details
- ISSN :
- 15206904 and 00223263
- Volume :
- 66
- Database :
- OpenAIRE
- Journal :
- The Journal of Organic Chemistry
- Accession number :
- edsair.doi.dedup.....bfd529522b90cfc6df802c6717a9fcd2