Expansion of the aromatic part of Cinchona alkaloids. Annulation of quinolines with phenoxazine motifs

An oxidative cross-coupling strategy for quinoline ring annulation in Cinchona alkaloids has been developed. Key-reaction optimization by changing oxidants and adjusting the nucleophilicity of the 2-aminophenols led to cupreine and cupreidine expanded with the phenoxazinone unit in 56–75% yield. The...

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Bibliographic Details
Published in:Tetrahedron 2018-01, Vol.74 (2), p.308-315
Main Authors: Wąsińska-Kałwa, Małgorzata, Giurg, Mirosław, Boratyński, Przemysław J., Skarżewski, Jacek
Format: Article
Language:English
Subjects:
Cinchona alkaloids
Conformational study
Oxidative cross-coupling
Phenoxazinones
Quinoline ring annulation
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Summary:An oxidative cross-coupling strategy for quinoline ring annulation in Cinchona alkaloids has been developed. Key-reaction optimization by changing oxidants and adjusting the nucleophilicity of the 2-aminophenols led to cupreine and cupreidine expanded with the phenoxazinone unit in 56–75% yield. The stereochemical integrity of the obtained alkaloid structures was confirmed by combined experimental and computed CD and NMR data. The conformational study revealed a fast equilibrium of the three conformers, differing in the orientation of the pyrido[a-3,2]phenoxazine moiety. [Display omitted]
ISSN:0040-4020
1464-5416
DOI:10.1016/j.tet.2017.11.072