engleski

Characterization of Cinchona alkaloids with NMR spectroscopy

Cinchona alkaloids are natural products isolated from the bark of the Cinchona tree and alkaloids isolated on industrial scale are quinine, quinidine, cinchonine and cinchonidine. They have interesting structure which includes bicyclic aliphatic quinuclidine ring and aromatic quinoline ring connected with a chiral carbon atom having hydroxyl group [1]. These alkaloids have diverse chemical applications, for example they are used as chiral resolving agents or chiral stationary phases for chromatographic separations as well as chiral catalysts or chiral ligands in asymmetric synthesis [2, 3]. In this study, transfer hydrogenation of cinchonidine and cinchonine over a palladium on carbon catalyst using formic acid/ammonium formate as hydrogen donor was studied and the course of reaction was monitored by 1H NMR spectroscopy. Since the peaks of NMR spectra of cinchona alkaloids are found in three distinct regions (aromatic, olefinic and aliphatic), monitoring of reaction was convenient to realize with 1H NMR spectroscopy. The structure of products of hydrogenation reactions was completely verified with 2D NMR spectroscopy techniques such as COSY, HSQC and HMBC and compared with unmodified alkaloids.

cinchonidine, cinchonine, reduction, NMR spectroscopy

nije evidentirano