Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cinchona Alkaloids”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1994

Comparative in vitro renal damage due to stereoisomeric cinchona alkaloids.

Cinchona alkaloids significantly diminished the ability of renal cortical slices to accumulate organic cations and organic anions in vitro. Stereoisomeric differences exist in the inhibition of the accumulation of p-amino hippurate and tetraethyl ammonium. Oxygen consumption in renal cortical slices was inhibited by all four cinchona alkaloids. Cinchonine/cinchonidine were stronger inhibitors of the in vitro oxygen consumption than quinine/quinidine. Common antimalarial drug chloroquine inhibited the organic anion and cation accumulation much higher concentration than primaquine. Renal cortical slice oxygen consumption was also inhibited at much higher concentration by chloroquine than primaquine. The results indicate adverse renal effects in vitro but the significance of these findings in vivo is to be further examined.

Animals↗
PubMed2005

Asymmetric Mannich reactions of beta-keto esters with acyl imines catalyzed by cinchona alkaloids.

Cinchona alkaloids catalyze the enantioselective Mannich reaction of beta-keto esters with acyl aryl imines. The reaction requires 10 mol % of cinchonine or cinchonidine. The reaction products are obtained in good yields (81-99%), high enantioselectivities (80-96% ee), and in diastereoselectivities that range from 1:1 to >95:5. The cinchonine-catalyzed reaction provides access to highly functionalized building blocks used in the asymmetric synthesis of a dihydropyrimidone and beta-amino alcohol.

Catalysis↗
PubMed2001

Enantioselective fluorination mediated by cinchona alkaloid derivatives/Selectfluor combinations: reaction scope and structural information for N-fluorocinchona alkaloids.

Cinchona-alkaloid/Selectfluor combinations efficiently fluorinate a variety of carbonyl compounds in a highly enantioselective manner to furnish chiral alpha-fluorocarbonyl compounds. The DHQB/Selectfluor combination is effective for the enantioselective fluorination of indanones and tetralones 1 in up to 91% ee. The first enantioselective syntheses of chiral derivatizing reagents 3 was accomplished with high ee and in high chemical yields by the DHQDA/Selectfluor combination. 3-Fluorooxindoles 7 were prepared with ee up to 83% using the (DHQ)2AQN/Selectfluor or the (DHQD)2PYR/Selectfluor combination. Since the combinations are conveniently prepared in situ from readily available reagents, the present system represents a practical method for enantioselective fluorination. X-ray crystallography and 1H NMR analyses of the cinchona alkaloids/Selectfluor combination have established that the species that mediate this novel reaction are N-fluoroammonium cinchona alkaloid tetrafluoroborates, which adopt open conformations.

Cinchona Alkaloids↗
PubMed2003

Synthesis of 9-N-cinchona alkaloid peptide hybrid derivatives: preparation and conformational study of 9-N-acylamino(9-deoxy)cinchona alkaloids.

The synthesis and conformational analyses of several 9-N-acylamino(9-deoxy)cinchona alkaloids is presented. Peptides were connected to cinchona alkaloids via a 9-amino group. The synthesis of the new cinchona alkaloid derivatives was performed straightforwardly from 9-amino(9-deoxy)dihydroquinidine via coupling with carboxylic acid chlorides and several dipeptides. Both alkaloid derivatives with the configuration of the corresponding natural product as well as its unnatural epimer were studied. The conformations of the prepared derivatives in solution were determined by NMR spectroscopy. It is shown that the conformation is strongly influenced by the configuration at the 9-position.

Cinchona Alkaloids↗
PubMed2000

Practical and highly enantioselective ring opening of cyclic meso-anhydrides mediated by cinchona alkaloids.

The cinchona alkaloid-mediated opening of prochiral cyclic anhydrides in the presence of methanol leading to optically active hemiesters is described. Very structurally diverse anhydrides are converted into their corresponding methyl monoesters, and either enantiomer can be obtained with up to 99% ee by using quinine or quinidine as directing additive. After the reaction, the alkaloids can be recovered almost quantitatively and reused without loss of enantioselectivity. Additionally, a catalytic protocol which permits the substoichiometric use of quinidine in the presence of easily accessible pentamethylpiperidine (pempidine) is presented.

Anhydrides↗
PubMed2000

Structure and Mechanism in Cinchona Alkaloid Chemistry: Aqueous Hydrolysis Proceeds with Complete Inversion or Complete Retention of Configuration We thank Stefanie Röper for experimental contributions, Olaf Schrake for discussion, Ulrike Eggert and Lars Ole Haustedt for their help, Dr. Hofer for NMR analysis, and two referees for their critical comments. Our work was supported by the Friedrich-Naumann-Stiftung (PhD. Fellowship for W.M.B.), Chininfabrik Buchler GmbH (gift of Cinchona alkaloids) and the Fonds der Chemischen Industrie.

Explore the source record for details and available documents.

Journal Article↗
PubMed1999

Stereoelectronic features of the cinchona alkaloids determine their differential antimalarial activity.

For most potent antimalarial activity, the cinchona alkaloids appear to require certain electronic features, particularly a sufficiently acidic hydroxyl proton and an electric field direction pointing from the aliphatic nitrogen atom towards the quinoline ring. These observations are the result of an analysis of molecular electronic properties of eight cinchona alkaloids and an in vivo metabolite calculated using ab initio 3-21G quantum chemical methods in relation to their in vitro IC50 values against chloroquine-sensitive and chloroquine-resistant Plasmodium falciparum parasites. The purpose is to provide a profile of the electronic characteristics necessary for potent antimalarial activity for use in the design of new antimalarial agents and to gain insight into the mechanistic path for antimalarial activity. Distinguishing features of the weakly active epiquinine and epiquinidine include a higher dipole moment, a different direction of the electric field, a greater intrinsic nucleophilicity, lower acidity of the hydroxyl proton, a lesser electron affinity of the lowest unoccupied molecular orbitals, and a higher proton affinity than the active cinchona alkaloids. A moderately potent quinine metabolite possesses some, but not all, of the same electronic features as the most potent cinchona alkaloids. Both the positioning of the hydroxyl and aliphatic amine groups and their electronic features appear to play a crucial role for antimalarial potency of the cinchona alkaloids, most likely by controlling the ability of these groups to form effective intermolecular hydrogen bonds.

Animals↗
PubMed2004

Asymmetric organic catalysis with modified cinchona alkaloids.

Insights into the role played by modified cinchona alkaloids in the Sharpless asymmetric dihydroxylation inspired studies of modified cinchona alkaloids as chiral organic catalysts that lead to the development of highly enantioselective alcoholyses for the desymmetrization, kinetic resolution, and dynamic kinetic resolution of cyclic anhydrides, cyanation of ketones, and 1,4-addition of thiols to cylic enones. These studies demonstrate the potential of modified cinchona alkaloids as broadly useful chiral organic catalysts for asymmetric synthesis.

Journal Article↗
PubMed2005

Cyclodextrins as carriers for cinchona alkaloids: a pH-responsive selective binding system.

A series of cyclodextrin-cinchona alkaloid inclusion complexes were prepared from beta-cyclodextrin, heptakis(2,6-di-O-methyl)-beta-cyclodextrin and heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin and four cinchona alkaloids in ca. 90% yields, and their inclusion complexation behavior was investigated at pH 7.2 and 1.5 by means of fluorescence, UV/Vis and 2D NMR spectroscopy. The results showed that the cinchona alkaloids can be efficiently encapsulated in the cyclodextrin cavity in an acidic environment and sufficiently released in a neutral environment, which makes these cyclodextrin derivatives the potential carriers for cinchona alkaloids. The binding ability and molecular selectivity of cyclodextrins toward cinchona alkaloids were discussed from the viewpoint of the size-fit concept and multiple recognition mechanism between host and guest.

Binding Sites↗
PubMed2000

New results on the mass spectra of cinchona alkaloids

The electrospray ionization (ESI) mass spectra of 16 cinchona alkaloid compounds were studied for the first time. The electron ionization (EI) spectra of 22 cinchona alkaloids were also recorded, 14 of which had not been examined previously. In the case of EI the characteristic direction of the fragmentation is the scission of the C8-C9 bond. Under EI the cleavage of the C4'-C9 bond occurs only in the case of hydrogenated cinchona alkaloids, whereas the C9-O bond cleavage can be observed in the case of ester and ether derivatives. At a low capillary exit voltage (CapEx) in the ESI measurements there is no fragmentation, and only the [M + H](+) and in some cases the double protonated [M + 2H](2+) ions can be detected. On increasing the CapEx the characteristic primary direction is the cleavage of the C9-O bond, which was observed in the case of epialkaloids and esterified or etherified cinchona derivatives, respectively. Copyright 2000 John Wiley & Sons, Ltd.

Journal Article↗
PubMed1994

Protection of carbon tetrachloride hepatotoxicity by cinchona alkaloids.

Elevated serum enzymes were observed due to all four cinchona alkaloids in male Sprague-Dawley rats after four day treatment. Only a slight effect on bile flow and excretion of phenolphthalein glucuronide in bile was noted. Animals treated with cinchona alkaloid for four days and then receiving CCl4 showed a partial protection against CCl4 induced hepatotoxicity. The levels of serum enzymes were lowered as compared to animals treated with CCl4 alone. Bile flow and excretion of phenolphthalein glucuronide in bile showed a trend of restoration towards control levels. All four cinchona alkaloids probably inhibit microsomal enzymes, thereby, inhibiting the bioactivation of CCl4 and hence reducing the toxicity.

Alanine Transaminase↗
PubMed2002

Highly selective hydroformylation of the cinchona alkaloids.

The four naturally occurring cinchona alkaloids were subjected to hydroformylation to create an extra functional group that allows immobilization. Cinchonidine, quinine, and quinidine, could be hydroformylated with virtually complete terminal selectivity, using a rhodium/tetraphosphite catalyst. The cinchonidine aldehyde was reduced to the alcohol and subjected to reductive amination with benzylamine.

Alcohols↗