László Töke

Studies on calix(aza)crowns, I. Synthesis, alkylation reactions and comprehensive NMR investigation of capped calix[4]arenes

Abstract Calix[4]arenes capped by diamide bridges in 1,3-position on the lower rim were synthesized. Regioselective alkylations of compounds 2 afforded 3, 4 O- and N-alkylated derivatives. Comprehensive NMR investigations were made to reveal the conformation of calix(aza)crowns 2, 3, 4.

A quantitative approach to optical resolution

Abstract Significant statistical relationships have been found between the parameters characterizing the results and circumstances of the resolutions of seventeen phenylglycine derivatives. The successful predictions given for the results of six independent resolutions prove the utility of these relationships.

Enantioselective Michael reaction of 2-nitropropane with substituted chalcones catalysed by chiral azacrown ethers derived from α-D-glucose

Abstract The chiral monoaza-15-crown-5 lariat ethers anellated to methyl-4,6-O-benzylidene-α- d -glucopyranoside 1a–c showed significant asymmetric induction as phase transfer catalysts in the Michael addition of 2-nitropropane to substituted chalcones. Among the catalysts bearing different side arms at the nitrogen atom, the compound with a phosphinoxidoalkyl side chain 1c proved to be the most effective (max. 78% e.e.). The type of substituent on the chalcone was found to have a very significant influence on both the chemical yield and the enantioselectivity of the reaction. The absolute configuration of the Michael adducts 3b and 3i was determined by chemical methods, while that of 3d was assigned by X-ray crystal structure determination.

d-Glucose-based azacrown ethers with a phosphonoalkyl side chain: application as enantioselective phase transfer catalysts

Abstract Five chiral α- d -glucose-based monoaza-15-crown-5 ethers with a phosphonoalkyl side chain 5a – e have been synthesized. The substituent at the nitrogen atom has a major influence on the cation extraction ability of the azacrown. The new lariat ethers 5a – e show significant asymmetric induction as phase transfer catalysts in the Michael addition of 2-nitropropane to chalcone.

Synthesis, extraction ability and application in asymmetric synthesis of azacrown ethers derived from D-glucose

New chiral monoaza-15-crown-5 ethers have been synthesised from 1,2:5,6-di-O-isopropylidene-D-mannitol. The substituent at the nitrogen atom has a major influence on the cation extraction ability of the azacrown. These sugar-based crown ethers show asymmetric induction as chiral phase transfer catalysts in the Michael addition of 2-nitropropane to chalcone (67% ee).

Studies on calix(aza)crowns, II. Synthesis of novel proximal doubly bridged calix[4]arenes by intramolecular ring closure of syn 1,3-and 1,2-ω-chloroalkylamides☆

Inherently chiral calix[4]arenes (9,10) with carboxamide bridges spanning the proximal positions on the lower rim and 18 achiral counterparts have been synthesized by double intramolecular cyclization of 7b,8b 1,3-and 17 1,2-bis-chloroalkylamides. The conformational analysis of the 1.3- and 1,2-disubstituted calixarene intermediates 5–8 and 15–17 proved an equilibrium of two distorted cone conformations. The success of ring closure was strictly dependent on the chain length of the open chain precursors.

Asymmetric Michael addition and deracemization of enolate by chiral crown ether

Abstract Crown ethers anellated to glucose units have been used to catalyse the enantioselective Michael addition of methyl phenylacetate to methyl acrylate in high chemical yields in up to 84% enantiomeric excess. A novel CH-acid deracemization has also been discovered and the mechanistic rationale of the asymmetric induction is discussed. The proposed mechanism of the addition was also substantiated by molecular mechanics calculations.

Zinc Selective Ionophores for Potentiometric and Optical Sensors

Abstract Iminodiacetamide derivatives were synthesized and studied as ionophores in plasticized poly(vinyl chloride) membranes with potentiometric and optical transduction. The N-benzyl and N-phenyl derivatives proved to have a distinct zinc selectivity preferring Zn2+ over Ca2+, Na+ by factors of 6×105 and 3×104. respectively. All ionophores exhibit a serious proton interference (log KPot Zn ++, H + - 6) which suggests that all application of this type of ionophores based sensors are limited to hydrogen ion buffer solution at pH ≥ 6.

An easy access to tetra-o-alkylated calix[4]arenes of cone conformation

Abstract Fully O-alkylated calix[4]arenes have been synthesized by the alkylation of p-tertbutylcalix[4]arene and its 1,3-dialkylated derivatives in liquid-liquid phase-transfer catalytic process. 1H 4 and 1H 2 R 2 could effeciently be deprotonated by aqueous NaOH (50% w/w)-toluene system and alkylated with alkyl (aralkyl, allyl) halogens in good yields affording calix[4]arene tetraethers of cone conformation.

Novel bis (crown ether)-based potassium sensor for biological applications

Based on structure-selectivity studies on bis-benzo-crown ether derivatives, 2,2′-bis[3,4-(15-crown-5)-2-nitrophenylcarbamoxymethyl]tetradecane (BME-44) was designed and synthesized. The performance characteristics of this new, highly lipophilic ionophore of the group of bis-nitrobenzo-15-crown-5 derivatives with urethane linkage when used in liquid membrane electrodes are evaluated with special regard to the requirements of biological and clinical applications. Potentiometric steady-state and flow-through dynamic data are presented to prove the sensor capabilities for clinical and physiological potassium determinations.