“…Dimers 209 along with crude metathesis mixtures were subsequently used in asymmetric iridium-catalyzed asymmetric hydrogenation of , -unsaturated carboxylic acids. Out of the studied compounds, the dimer ( aR )- QN-209 provided up to 92 %ee and outperformed the initial monomer ( ee 8–32 %) [ 138 ]. Fig.…”
Nature is full of dimeric alkaloids of various types from many plant families, some of them with interesting biological properties. However, dimeric Cinchona alkaloids were not isolated from any species but were products of designed partial chemical synthesis. Although the Cinchona bark is amongst the sources of oldest efficient medicines, the synthetic dimers found most use in the field of asymmetric synthesis. Prominent examples include the Sharpless dihydroxylation and aminohydroxylation ligands, and dimeric phase transfer catalysts. In this article the syntheses of Cinchona alkaloid dimers and oligomers are reviewed, and their structure and applications are outlined. Various synthetic routes exploit reactivity of the alkaloids at the central 9-hydroxyl group, quinuclidine, and quinoline rings, as well as 3-vinyl group. This availability of reactive sites, in combination with a plethora of linker molecules, contributes to the diversity of the products obtained.
“…Dimers 209 along with crude metathesis mixtures were subsequently used in asymmetric iridium-catalyzed asymmetric hydrogenation of , -unsaturated carboxylic acids. Out of the studied compounds, the dimer ( aR )- QN-209 provided up to 92 %ee and outperformed the initial monomer ( ee 8–32 %) [ 138 ]. Fig.…”
Nature is full of dimeric alkaloids of various types from many plant families, some of them with interesting biological properties. However, dimeric Cinchona alkaloids were not isolated from any species but were products of designed partial chemical synthesis. Although the Cinchona bark is amongst the sources of oldest efficient medicines, the synthetic dimers found most use in the field of asymmetric synthesis. Prominent examples include the Sharpless dihydroxylation and aminohydroxylation ligands, and dimeric phase transfer catalysts. In this article the syntheses of Cinchona alkaloid dimers and oligomers are reviewed, and their structure and applications are outlined. Various synthetic routes exploit reactivity of the alkaloids at the central 9-hydroxyl group, quinuclidine, and quinoline rings, as well as 3-vinyl group. This availability of reactive sites, in combination with a plethora of linker molecules, contributes to the diversity of the products obtained.
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