Cinchonidine structure

Moreover, bulk MIP was prepared [56] exhibiting diastereoselectivity for cinchona alkaloids. In the presence of MIP in solution, the cinchonidine fluorescence emission was hypsochromically shifted with the increase of the cinchonide concentration. That is, maximum of the fluorescence emission was at 390 nm in the absence of cinchonidine whereas it was at 360 nm at higher concentrations of cinchonidine. When cinchonidine was examined in the absence of MIP or in the presence of NIP, there was no spectral shift or this shift was negligibly small. This shift has been explained on the basis of protonation of the nitrogen atoms present in the cinchonidine structure. 

The directions of rotation at C and C have been arrived at from the following considerations. The deoxy-bases (II p. 443 Q = quinoline residue) obtained from cinchonine and cinchonidine are structurally identical, i but optically different, and since they must be optically identical at C and C, and C is no longer asymmetric, the difference between them (see table, p. 446) must be due to difference in direction of rotation at C , which must therefore be dextrorotatory in cinchonine and laevorotatory in cinchonidine, and this must also be true of quinidine and quinine respectively and of the corresponding dihydro-bases. The keto-bases, cinchoninone and quininone, might be expected to exist each in two pairs, since carbon atom 8 is, according to the formula (p. 442), asymmetric, but it is better represented by the tautomeric grouping —... 

Cinchona PelUtierana, alkaloids, 466 Cinchona spp., alkaloids, 418, 424 Cinchona, total alkaloids. See Totaquina. Cinchonamine, 419, 465 Cinchonhydrines, 440, 452 Cinchonicine (cinchotoxine), 410, 442, 451 Cinchonidine, 419, 427 constitution, 435 apoCinchonidlne, 448, 452 J3-Cinchonidine, 448, 452 Cinchonifine (dihydrocinchonine) 428 Cinchonine, 410, 421, 427, 583 constitution, 435 oxidation, 436 structural formula, 442 /leieroCinchonine (/i-cinchonine), 451 isoCinchonines, 451 Cinchoninic acid, 454 Cinchonino, 421 Cinchoninone, 437, 438, 442 Cinchotenidine, 436 Cinchotenine, 436... 

Theoretical studies aimed at rationalizing the interaction between the chiral modifier and the pyruvate have been undertaken using quantum chemistry techniques, at both ab initio and semi-empirical levels, and molecular mechanics. The studies were based on the experimental observation that the quinuclidine nitrogen is the main interaction center between cinchonidine and the reactant pyruvate. This center can either act as a nucleophile or after protonation (protic solvent) as an electrophile. In a first step, NH3 and NH4 have been used as models of this reaction center, and the optimal structures and complexation energies of the pyruvate with NH3 and NHa, respectively, were calculated [40]. The pyruvate—NHa complex was found to be much more stable (by 25 kcal/mol) due to favorable electrostatic interaction, indicating that in acidic solvents the protonated cinchonidine will interact with the pyruvate. 

Figure 3. Structures of quinine, cinchonidine, quinidine, and cinchonine.

The structures of quinine, cinchonidine, quinidine, and cinchonine are shown in Figure 3. Other workers (16,17) have discussed these alkaloids and their use as catalysts in some detail. An excellent discussion of cinchona-alkaloid-catalyzed reactions prior to 1968 was given by Pracejus (18). In this section we discuss only four aspects of these reactions. 

A limited study has been made of the role of the structure of the catalyst in the phase-transfer epoxidation reaction (77). The catalysts tried were mainly salts of quinine (3a-g), cinchonidine (4), ephedrine (5), and a camphor derivative (6) (Figure 14). The conclusions were as follows ... 

The replacement of the oxygen atom in sulfoxides by nitrogen leads to a new class of chiral sulfur compounds, namely, sulfimides, which recently have attracted considerable attention in connection with the stereochemistry of sulfoxide-sulfimide-sulfoximide conversion reactions and with the steric course of nucleophilic substitution at sulfur. The first examples of chiral sulfimides, 88 and 89, were prepared and resolved into enantiomers by Phillips (127,128) by means of the brucine and cinchonidine salts as early as 1927. In the same way, Kresze and Wustrow (129) were able to separate the enantiomers of other structurally related sulfimides. 

This structural group of indole alkaloids covers simple indole alkaloids (e.g., tryptamine, serotonin, psilocin and psilocybin), /3-carboline alkaloids (e.g., harmine), terpenoid indole (e.g., ajmalicine, catharanthine and tabersonine), quinoline alkaloids (e.g., quinine, quinidine and cinchonidine), pyrroloindole... 

This group of alkaloids has two structurally different a. The a of alkaloids found in the genus Cinchona (Ruhiaceae), such as quinine, quinidine, cinchonidine and cinchonine, is L-tryptophan. The j8 is tryptamine and the

[Pg.114]

In the presence of a cinchona alkaloid, certain cyclic carboxylic anhydrides with meso structures are converted to the chiral diacid monoesters in up to 76% ee (Scheme 10) 31). Quinine or cinchonidine and quinidine or cinchonine show opposite asymmetric induction. 

The Pt-cinchonidine system is a promising catalyst for the enantioselective hydrogenation of a,a,a-trifluoromethyl ketones to the corresponding alcohols. The ee varies in a broad range between 5 and 90 %, depending on the chemical nature of the R group in the general structure F3C-CO-R. The remarkable differences may be well explained by steric and electronic effects. 

What makes cinchona alkaloids so unique in the molecular world The complex structure and multifunctional character of the four principal members of the cinchona alkaloid family - quinine, quinidine, cinchonine (CN), and cinchonidine... 

Figure 13.2 Structural features of cinchona alkaloid molecules (QN, quinine QD, quinidine CN, cinchonine CD, cinchonidine CPN, cupreine CPD, cupreidine).

The X-ray-determined structure of the complex of 16 and 19 with quaternary salt 15 revealed that the primary discriminative forces leading to an efficient resolution are the formation of directional hydrogen bonds of hydroxy groups of cinchonidine and BINOL with the halide anion as well as aryl-aryl interaction between the naphthyl and the quinoline rings [40]. 

Quinine (2) is the major active principle of cinchona, which was isolated by Pelletier and Caventou in 1820 [16] however, its structure could only be established after 100 years [17]. The total synthesis of quinine was accomplished by Woodward and Doering [18] and others [19] but none of the synthetic methods are economical and, therefore, can not compete with the natural production of quinine the bark of the cinchona tree is still the only source of the drug. In addition to quinine (2), three more antimalarial components, quinidine (3), cinchonidine (4) and cinchonine (5) are present in the bark. 

This paper deals with the asymmetric hydrogenation of ethyl pyruvate to ethyl lactate showing a high enantiomeric excess in favour of the R-enantiomer over (-)cinchonidine modified Pt/carrier catalysts. Due to their regular structures, zeolites in particular have been used as carrier materials. 

For almost two centuries, the bark was used in medicine as a powder, extract, or infusion. In 1820 Pelletier and Caventou isolated quinine and cinchonine from cinchona, and the use of the alkaloids as such gained favor rapidly. Extensive and classic studies led to elucidation of the structure of quinine (Figure 2) (4) and to its total synthesis in 1944 (5). Cinchona contains 25 closely related alkaloids, of which the most important are quinine, quinidine, cinchonine, and cinchonidine. The average yield of alkaloid is about 6-7 %, of which one-half to two-thirds is quinine. It has been said that quinine owes its dominant position in the treatment of malaria only to the fact that it was the first alkaloid isolated from cinchona, and that there is little among the four major alkaloids to choose from in treating this disease (6). 

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