Cinchonidine

Chiral modification of copper exchanged zeolite-Y with cinchonidine and its application in the asymmetric Henry reaction.[Pubmed:26579982]

Dalton Trans. 2015 Dec 28;44(48):20949-63.

Chirally modified Cu(2+) exchanged zeolite-Y was synthesized by direct adsorption of Cinchonidine under ambient conditions. The chirally modified materials were characterized using various spectrochemical and physicochemical techniques viz. BET, FTIR, MAS ((1)H and (13)C NMR), XPS, SEM, cyclic voltammetry and PXRD. Characteristic peaks of Cinchonidine observed in the supported materials confirmed the adsorption of Cinchonidine and its coordination with the Cu(2+) active site on copper exchanged zeolite-Y. (13)C SSNMR and XPS analysis however confirmed for the half encapsulation process, only the quinoline ring of Cinchonidine gets coordinated to the internal metal sites via the N atom while the quinuclidine moiety extends out of the host surface. Cinchonidine supported Cu(2+)-Y zeolites were found to exhibit good catalytic performance in the asymmetric Henry reaction. (1)H SSNMR studies also confirmed the protonation of the N atom of the quinuclidine ring during the course of the Henry reaction. Heterogeneous chiral catalysts were effective for up to two consecutive cycles. Leaching of Cinchonidine after the second cycle was found to have a negative result in the catalytic performance.

Exotic Protonated Species Produced by UV-Induced Photofragmentation of a Protonated Dimer: Metastable Protonated Cinchonidine.[Pubmed:26347997]

J Phys Chem A. 2015 Oct 1;119(39):10007-15.

A metastable protonated cinchona alkaloid was produced in the gas phase by UV-induced photodissociation (UVPD) of its protonated dimer in a Paul ion trap. The infrared multiple photon dissociation (IRMPD) spectrum of the molecular ion formed by UVPD was obtained and compared to DFT calculations to characterize its structure. The protonation site obtained thereby is not accessible by classical protonation ways. The protonated monomer directly formed in the ESI source or by collision-induced dissociation (CID) of the dimer undergoes protonation at the most basic alkaloid nitrogen. In contrast, protonation occurs at the quinoline aromatic ring nitrogen in the UVPD-formed monomer.

Influences of urea and pH on the interaction of cinchonidine with bovine serum albumin by steady state fluorescence spectroscopy.[Pubmed:23651774]

Spectrochim Acta A Mol Biomol Spectrosc. 2013 Aug;112:15-20.

The binding of Cinchonidine to bovine serum albumin (BSA) in aqueous solution in the absence and presence of urea has been studied by fluorescence spectroscopic techniques at pH 7.40. Denaturation of BSA in the presence of urea is almost complete at [urea] >/=8.0 M. Upon unfolding, two fluorescence peaks of BSA were observed. One peak was assigned to the fluorescence of Trp residue in a polar environment, and the other peak was assigned to the fluorescence of Tyr residues. In addition, the fluorescence quenching effects of Cinchonidine were shown not only on the native but also on the unfolded form of BSA. The quenching rate constants and binding constants calculated in the absence and presence of the denaturant urea indicates that the binding capacity of Cinchonidine to the denatured BSA deceases dramatically. In addition, influence of pH on the interaction between Cinchonidine and BSA was investigated and the binding abilities of the drug to BSA deceased under lower pH conditions (pH 3.5 and 1.8) and higher pH conditions (pH 9.0).

Chiral modification of platinum by co-adsorbed cinchonidine and trifluoroacetic acid: origin of enhanced stereocontrol in the hydrogenation of trifluoroacetophenone.[Pubmed:24382788]

Chemistry. 2014 Jan 27;20(5):1298-309.

Cinchonidine (CD) adsorbed onto a platinum metal catalyst leads to rate acceleration and induces strong stereocontrol in the asymmetric hydrogenation of trifluoroacetophenone. Addition of catalytic amounts of trifluoroacetic acid (TFA) significantly enhances the enantiomeric excess from 50 to 92%. The origin of the enantioselectivity bestowed by co-adsorbed CD and TFA is investigated by using in situ attenuated total reflection infrared spectroscopy and modulation excitation spectroscopy. Molecular interactions between the chiral modifier (CD), acid additive (TFA) and the trifluoro-activated substrate at the solid-liquid interface are elucidated under conditions relevant to catalytic hydrogenations, that is, on a technical Pt/Al2O3 catalyst in the presence of H2 and solvent. Monitoring of the unmodified and modified surface during the hydrogenation provides an insight into the phenomenon of rate enhancement and the crucial interactions of CD with the ketone, corresponding product alcohol, and TFA. Comparison of the diastereomeric interactions occurring on the modified surface and in the liquid solution shows a striking difference for the chiral preferences of CD. The spectroscopic data, in combination with calculations of molecular structures and energies, sheds light on the reaction mechanism of the heterogeneous asymmetric hydrogenation of trifluoromethyl ketones and the involvement of TFA in the diastereomeric intermediate surface complex: the quinuclidine N atom of the adsorbed CD forms an N-H-O-type hydrogen-bonding interaction not only with the trifluoro-activated ketone but also with the corresponding alcohol and the acid additive. Strong evidence is provided that it is a monodentate acid/base adduct in which the carboxylate of TFA resides at the quinuclidine N-atom of CD, which imparts a better stereochemical control.

Cinchonidine (α-Quinidine) is a cinchona alkaloid found in Cinchona officinalis and Gongronema latifolium. A building block used in asymmetric synthesis in organic chemistry. Weak inhibitor of serotonin transporter (SERT) with Kis of 330, 4.2, 36, 196, 15 μM for dSERT, hSERT, hSERT I172M, hSERT S438T, hSERT Y95F, respectively. Antimalarial activities.

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