Functional polymers. 6. Unusual catalysis of polymeric cinchona alkaloids in asymmetric reaction

Acrylonitrile-cinchona alkaloid copolymers catalyzed the asymmetric addition of benzyl mercaptan to 2-nitrostyrene to give always (+)-enantiomer in excess, indicating the participation of C(3)-chirality in the enantioface differentiating step.     

Functional polymers with cyclic ether moieties. II. Synthesis and properties of network polymers with tetrahydrofuran moiety

A tetrahydrofuran (THF)‐containing network polymer was prepared by the radical suspension copolymerization of a styrene (St)‐type monomer with THF moiety, St, p‐chloromethylstyrene, and divinylbenzene in a biphasic medium consisting of water and monochlorobenzene in the presence of acacia gum as a suspension stabilizer. The diameters of the obtained polymer beads ranged from 100 to 200 μm. The obtained network polymer showed higher swelling abilities in various organic solvents than a similarly prepared network polymer without THF moiety, and it was stable under oxidative, reductive, and basic conditions. In its derivations to polystyrene‐based resins with thioether alcohol and hydroxyl moiety, remarkable accelerations of reactions were observed as a result of the introduction of THF moiety. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 800–806, 2001     

Highly stereoselective, uniformly sized molecularly imprinted polymers for cinchona alkaloids in hydro-organic mobile phases.

Highly stereoselective, uniformly sized molecularly imprinted polymers (MIPs) for cinchona alkaloids, cinchonine (CN) and cinchonidine (CD), were prepared using methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate (EDMA) as a cross-linker. The MIPs were evaluated using a mixture of phosphate buffer and acetonitrile as the mobile phase. The CN- and CD-imprinted MAA-co-EDMA polymers can recognize the respective template molecule more than the other diastereomer, and afford an excellent diastereomer separation of CN and CD. In addition, the MIPs gave diastereomer separations of structurally related compounds, quinidine and quinine. The retentive and stereoselective properties of those compounds on the MIPs suggest that electrostatic and hydrophobic interactions can work to recognize these compounds. Furthermore, thermodynamic studies reveal that the entropy-driven effect is significant at mobile-phase pH 5.4, while the enthalpy-driven interactions seem to be dominant at mobile-phase pH 9.6.     

Synthesis and properties of new potentially nonthrombogenic polymeric materials

A new family of block copolymers have been synthesized and characterized. These copolymers have a central block deriving from the polyaddition of N,N′-dimethylethylenediamine to 1,4-bis-acryloylpiperazine, and lateral blocks of polystyrene. Preliminary biocompatibility tests have demonstrated that these new products show promise as long-acting nonthrombogenic materials.     

Functional polymers. III. Asymmetric Michael reactions catalyzed by cinchona alkaloid–acrylonitrile copolymers

The enantio-differentiating abilities of cinchona alkaloid–acrylonitrile copolymers (AN–CA) in the Michael reactions were studied. The reaction of methyl indan-1-one-2-carboxylate (I) with methyl vinyl ketone in toluene at room temperature yielded product (II) in 24–42% optical yield, depending on the type and frequency of the alkaloid units on the polymeric skeleton. The catalysts were recovered from the reaction mixture by filtration and with retention of their stereoselectivities. Modification of the amino or hydroxyl group of the alkaloid moiety greatly reduced the reaction rate and optical yield. The asymmetric reactions of other donors (III–VII) with methyl vinyl ketone were also studied.     

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.     

Synthesis and properties of new polymeric surfactant with quaternary ammonium salt

The polymeric surfactant with quaternary ammonium salt (PQ) was synthesized by cationic ring-open polymerization using boron trifluoride diethyletherate as cationic catalyst. The chemical structure and aggregation behavior of PQ were studied by ¹H NMR, surface tension, static light scattering, dynamic laser light scattering, electrical conductivity, and fluorescence measurement. The results show the surface tension (γ_cmc) and critical micelle concentration (cmc) of PQ decrease with increasing of sodium chloride concentration. The cmc and γ_cmc values of PQ measured by electrical conductivity and fluorescence measurements mainly identify with that obtained by surface tension measurements. The thermodynamic parameters (DG_m⁰ \Delta G_m^0 ,DH_m⁰ \Delta H_m^0 ,DS_m⁰ \Delta S_m^0 ) from electrical conductivity indicated that the micellization of PQ was mainly the process of entropy-driven. In addition, the results from the viscosity stability between hydrolyzed polyacrylamide (HPAM) and PQ showed that the viscosities of mixed system for HPAM and PQ are higher than the viscosity of HPAM.     

Binding behaviour and solubilisation of p-sulfonatocalixarenes to cinchona alkaloids

In this study, we investigated the binding behaviours of three water-soluble p-sulfonatocalixarenes with four cinchona alkaloids in aqueous and phosphate buffer solutions (pH 7.2 and 2.0). The complexation stability constants obtained by fluorescence titrations were comparatively discussed from several aspects: host cavity, pH effect and ionic strength. Among three hosts, p-sulfonatocalix[4]arene (SC4A) forms the most stable complexes with cinchona alkaloids, especially in acidic aqueous conditions. Furthermore, SC4A was elected as model drug carrier for cinchona alkaloids, where solubilisation by the complexation of SC4A and mimic release from the calixarene cavity in the presence of negatively charged micelles were initially studied.     

Liquid chromatographic analysis of cinchona alkaloids in beverages

A method for the determination of Cinchona extract (whose main components are the alkaloids cinchonine, cinchonidine, quinidine, and quinine) in beverages by liquid chromatography was developed. A beverage with an alcohol content of more than 10% was loaded onto an OASIS HLB solid-phase extraction cartridge, after it was adjusted to pH 10 with 28% ammonium hydroxide. Other beverages were centrifuged at 4000 rpm for 5 min, and the supernatant was loaded onto the cartridge. The cartridge was washed with water followed by 15% methanol, and the Cinchona alkaloids were eluted with methanol. The Cinchona alkaloids in the eluate were chromatographed on an L-column ODS (4.6 mm id x 150 mm) with methanol and 20 mmol/L potassium dihydrogen phosphate (3 + 7) as the mobile phase. Cinchona alkaloids were monitored with an ultraviolet (UV) detector at 230 nm, and with a fluorescence detector at 405 nm for cinchonine and cinchonidine and 450 nm for quinidine and quinine (excitation at 235 nm). The calibration curves for Cinchona alkaloids with the UV detector showed good linearity in the range of 2-400 microg/mL. The detection limit of each Cinchona alkaloid, taken to be the concentration at which the absorption spectrum could be identified, was 2 microg/mL. The recovery of Cinchona alkaloids added at a level of 100 microg/g to various kinds of beverages was 87.6-96.5%, and the coefficients of variation were less than 3.3%. A number of beverage samples, some labeled to contain bitter substances, were analyzed by the proposed method. Quinine was detected in 2 samples of carbonated beverage.     

Microdetermination of cinchona alkaloids by atomic absorption spectroscopy

A sensitive and rapid microdetermination method has been developed for the determination of cinchona alkaloids via their mercury complex. Different parameters of the procedure have been thoroughly studied. The percentage recoveries for quinine, quinidine, cinchonine and cinchonidine were found to be 98.97 ±0.62, 99.06 ± 0.62, 98.90 ± 0.74, respectively. The results obtained are favourably compared to the official ones. The method is characterised by its specificity, accuracy and good precision.     

A new class of urea-substituted cinchona alkaloids promote highly enantioselective nitroaldol reactions of trifluoromethylketones

The first class of bifunctional cinchona-alkaloid catalysts incorporating a urea moiety at C-5' has been developed. These materials catalyze the efficient and highly enantioselective 1,2-addition of nitromethane to trifluoromethylketones to form synthetically pliable products incorporating a quaternary stereocenter. Excellent product yields and levels of enantiomeric excess are possible, and the optimum catalyst structure is capable of promoting the Henry reaction involving alkyl trifluoromethylketones with unprecedented enantioselectivity.     

Synthesis and properties of new polyazines—II

New polyazines have been synthesized by the polycondensation of 9,10-phenanthrenequinone, 9,10-anthraquinone, 1- and 2-chloroanthraquinone with hydrazine hydrate and disulphinylhydrazine. A reaction mechanism has been proposed for the polycondensation of phenanthrenequinone with hydrazine hydrate in DMF in the presence of zinc chloride. The electrical conductivity (10^?10–10^?6 ohm^?1 cm^?1) and the paramagnetic particle concentration (10¹⁸–10²¹ spin/g indicate the semiconducting properties of these polyazines.     

Synthesis and liquid crystal alignment properties of new cinnamate-based photocrosslinkable polymers

Because optical buffing can achieve aligning patterns with different azimuthal angles of the liquid crystal directors, photoalignment appears to be a very hopeful technique for designing complex LCD structures. Until recently, most photopolymers provided low anchoring and/or low tilt angles which are unsuitable for industrial applications. In this work, four new photocrosslinkable polymers based on biphenyl and naphthalene moieties have been prepared and characterized. These photopolymers have been irradiated with linearly polarized UV light, and liquid crystal cells have been made. The tilt angles generated by oblique irradiation have been measured as well as the anchoring energies. Finally, the stability of the liquid crystal alignment properties have been studied.     

Sulfur-containing polymers. II. Preparation and properties of polycarbamoylsulfenamides

Polycarbamoylsulfenamides have been prepared by interfacial and solution polycondensation of chlorocarbonylsulfenyl chloride with diamines. In preparing the polycarbamoylsulfenamides, the following types of diamines were used: primary aliphatic diamines, a mixed primary-secondary aliphatic diamine, primary aromatic diamines, and secondary aromatic diamines. The properties of the resulting polymers depended primarily on the kind of diamines used. Transparent, tough films were obtained from the polymer based on N,N′-dimethyl-4,4′-diaminodiphenylmethane. The photochemical decomposition of the polymers has been studied.