Iridium-promoted deoxyglycoside synthesis: stereoselectivity and mechanistic insight

Herein, we devised a method for stereoselective O-glycosylation using an Ir(i)-catalyst which enables both hydroalkoxylation and nucleophilic substitution of glycals with varying substituents at the C3 position. In this transformation, 2-deoxy-α-O-glycosides were acquired when glycals equipped with...

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Detalles Bibliográficos
Autores principales: Pal, Kumar Bhaskar, Guo, Aoxin, Das, Mrinmoy, Lee, Jiande, Báti, Gábor, Yip, Benjamin Rui Peng, Loh, Teck-Peng, Liu, Xue-Wei
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The Royal Society of Chemistry 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8179265/
https://www.ncbi.nlm.nih.gov/pubmed/34163986
http://dx.doi.org/10.1039/d0sc06529c
Descripción
Sumario:Herein, we devised a method for stereoselective O-glycosylation using an Ir(i)-catalyst which enables both hydroalkoxylation and nucleophilic substitution of glycals with varying substituents at the C3 position. In this transformation, 2-deoxy-α-O-glycosides were acquired when glycals equipped with a notoriously poor leaving group at C3 were used; in contrast 2,3-unsaturated-α-O-glycosides were produced from glycals that bear a good leaving group at C3. Mechanistic studies indicate that both reactions proceed via the directing mechanism, through which the acceptor coordinates to the Ir(i) metal in the α-face-coordinated Ir(i)-glycal π-complex and then attacks the glycal that contains the O-glycosidic bond in a syn-addition manner. This protocol exhibits good functional group tolerance and is exemplified with the preparation of a library of oligosaccharides in moderate to high yields and with excellent stereoselectivities.