Ferrocene Derivatization Reagents for Optical Resolution of Carboxylic Acids by High-performance Liquid Chromatography with Electrochemical Detection

Abstract

New derivatization methods using chiral ferrocene reagents have been developed for the optical resolution of carboxylic acids by high-performance liquid chromatography with electrochemical detection. Two chiral derivatization reagents, 1-ferrocenylethylamine and 1-ferrocenylpropylamine, were readily prepared from acetylferrocene and propionylferrocene in two steps, respectively. Condensation of carboxylic acids with the chiral reagent was effected in the presence of water-soluble carbodiimide and 1-hydroxybenzotriazole. The diastereomeric amides formed from N-acetylamino acid and α-arylpropionic acid enantiomers were efficiently resolved by reversed-phase chromatography and showed the satisfactory sensitivity at +0.45 V vs. an Ag/AgCl reference electrode with a detection limit of 0.5 pmole (S/N=5).     

On the Stability of Isoindole-Type Fluorophores Derived from O-Phthalaldehyde,Primary Amino Compounds and Thiols

Abstract

o-Phthalaldehyde (OPA), a primary amino compound and a thiol react to produce a ternary isoindole-type fluorophore. The effect of the structure of the constituent amino compound on the chemical stability of isoindole fluorophores was investigated. The amino compounds with steric hindrance around the -NH₂ group such as L-tryptophan and L-Dopa exhibited a marked stabilization effect on the isoindole fluorophores. By using OPA and L-typtophan as reagents, a procedure was established for the fluorometric determination of thiols which permitted the determination of 2 nmol of L-cysteine (CySH). The possible mechanism for the instability of isoindole accelerated by increasing concentration of OPA was also discussed.     

A Chemiluminiscence Detector for Trace Determination of Fluorescent Compounds

Abstract

A detector making full use of the advantages offered by chemiluminiscence has been constructed. Light measurement was performed with modern electronic equipment using photon counting and the system was tested using dansyl derivatives of adrenaline, noradrenaline and of some amino acids. The detection limits for the two catecholamines were 6 and 16 fmol, respectively, and less than 0.5 fmol for the amino acids. To reach these low levels all reagents were purified or selected for ultra-high purity. The effects of reagent contaminants and of various optical filters have been studied using adrenaline as the test substance.     

Determination of Fatty Acids by High-Performance Liquid Chromatography with Electrochemical Detection Using A Ferrocene Derivatization Reagent

Abstract

New derivatization method using ferrocene reagents has been developed for the determination of fatty acids by high-performance liquid chromatography with electrochemical detection. Condensation of fatty acids with 3-bromoacetyl-1, 1'-dimethyl-ferrocene was effected in the presence of 18-crown-6 and potassium fluoride. The resulting esters showed the satisfactory sensitivity at +0.60 V vs. an Ag/AgCl reference electrode with a detection limit of 0.5 pmole. Also the high selectivity was obtained by using a twin electrode electrochemical detector. The proposed derivatization method was found applicable to the determination of fatty acids in human serum.     

Mannose‐BSA Conjugates: Comparison Between Commercially Available Linkers in Reactivity and Bioactivity

Mannosyl ethanolamine and BSA were conjugated together by their amino groups with various homobifunctional cross‐linker reagents: disuccinimidyl carbonate (DSC), disuccinimidyl glutarate (DSG), disuccinimidyl suberate (DSS), ethylene glycolbis(succinimidylsuccinate) (EGS), 1,5‐difluoro‐2,4‐dinitrobenzene (DFDNB), diethyl squarate (DES), and thiophosgene (TP). The resulting mannose-BSA conjugates were subjected to an enzyme‐linked lectin assay (ELLA)to investigate their affinity to concanvalin A (ConA). With these results, the seven linkers were evaluated on the basis of five criteria, i.e., cost, reactivity, sugar loading, homogeneity, and affinity to ConA. Thus, DSS, DFDNB, and DES seemed to have advantages over the other cross-linking reagents.     

Aminophosphinidene derivatives

Abstract

Elimination and fragmentation reactions lead to carbene analogous iminophosphanes which undergo 2 + 1 addition as well as insertion reactions. Secondary aminophosphanes and amino substituted three-membered phosphorus rings are phosphinidene transfer reagents and therefore valuable building units for cyclic and acyclic compounds. Synthetic routes to amino substituted diphosphenes and their reaction behaviour are reported.     

A green approach for the electroorganic synthesis of 2-[(4-methyl-2-pyridyl)amino]-1,4-benzenediol derivatives in aqueous solution

The electrochemical synthesis of some new 2-[(4-methyl-2-pyridyl)amino)-1,4-benzenediol derivatives was performed via the electrochemical oxidation of hydroquinones in the presence of 2-amino-4-methylpyridine in an aqueous solution. The results demonstrate that electrogenerated p-benzoquinone participated in the Michael-type addition reaction via an electrochemical–chemical (EC) reaction mechanism pathway and converted to the corresponding 2-[(4-methyl-2-pyridyl)amino)-1,4-benzenediol derivatives. These new compounds have been synthesized in high yields and purity without using any toxic reagents or catalyst at the surface of carbon electrode.     

A Convenient Synthesis of 3-Benzoylindolizine-5-carbaldehydes

3-Benzoylindolizine-5-carbaldehydes (4a-f), which could be used as derivatization reagents for amino compounds in HPCE were synthesized based on the 1,3-dipolar cycloaddition of 1-phenacyl-2-(1,3-dioxolan-2-yl)pyridinium ylide with alkenes in the presence of TPCD.     

Sensitive ferrocene reagents for derivatization of amines for high-performance liquid chromatography with electrochemical detection

Six reagents possessing ferrocene as an electrophore were prepared and evaluated for pre-column derivatization of amino compounds for their determination by high-performance liquid chromatography with electrochemical detection. The utility of these reagents was investigated employing phenethylamine as a model compound. Among these six, N-succinimidyl 3-ferrocenylpropionate was the best with respect to reactivity, stability and electrochemical properties. The developed method was applied to the determination of putrescine formed from ornithine by ornithine decarboxylase.     

Electrochemical behavior and determination of L-tryptophan on carbon ionic liquid electrode

A carbon ionic liquid electrode (CILE) was fabricated by mixing N-butylpyridinium hexafluoro-phosphate (BPPF ₆ ) with graphite powder and further used for the investigation on the electrochemical behavior of L-tryptophan (Trp). The fabricated CILE showed good conductivity, inherent electrocatalytic ability and strong promotion to the electron transfer of Trp. On the CILE, an irreversible oxidation peak appeared at 0.948 V (vs. saturated calomel reference electrode). For 5.0 × 10⁻⁵ M Trp the oxidation peak current increased about 5 times and the oxidation peak potential decreased on 0.092 V compared to carbon paste electrode. The results indicated that an electrocatalytic reaction occurred on CILE. The conditions for the electrochemical detection were optimized and the electrochemical parameters of Trp on CILE were carefully investigated. Under the selected conditions, the oxidation peak current showed linear relationship with Trp concentration in the range of 8.0 × 10⁻⁶ ∼1.0 × 10⁻³ M for cyclic voltammetry and the detection limit was estimated as 4.8 × 10⁻⁶ M (3σ). The interferences of other amino acids or metal ions on the determination were tested and the proposed method was successfully applied to the synthetic sample analysis.     

Radioprotective and Antitumor Activity of Some Novel Amino Acids and Imidazoles Containing Thieno[2,3-d]pyrimidine Moiety

A variety of novel thieno[2,3-d]pyrimidine derivatives, comprising amino acids 3a–l, imidazothieno-pyrimidines 4A, 4b–h, and 7, were obtained via the reaction of 4-chloro-5,6-dimethylthieno[2,3-d]pyrimidine 1 with a variety of reagents. The structures of these compounds were confirmed by microanalysis, IR, ¹H NMR, and mass spectrometry. Some of the obtained compounds showed promising radioprotective and antitumor activities.     

Effects of Different Stationary Phases and Surfactant or Cyclodextrin Spray Reagents on the Fluorescence Densitometry of Polycyclic Aromatic Hydrocarbons and Dansylated Amino Acids

Abstract

The detectable luminescence of twelve dansy1 amino acids and four polycyclic aromatic hydrocarbons (PAH's) spotted on five common TLC stationary phases was evaluated. The detectable luminescence varied appreciable for compounds associated with different stationary phases. The use of surfactant and cyclodextrin spray reagents caused luminescence enhancements on some stationary phases but not others. The reagents did not affect all compounds to the same degree indicating that qualitative information could be obtained in some cases. The largest luminescence increase for a compound spotted on silica gel was for pyrene (i.e., 47-fold) sprayed with sodium cholate. The degree to which the plates were dried also affected the luminescence intensity. Possible reasons for the observed effects are discussed.     

Electrochemical Determination of Xanthine Oxidase-Catalyzed Oxidation of Xanthine

Abstract

A rapid electrochemical (chronoamperometric) method for the determination of xanthine oxidase catalyzed oxidation of xanthine and hypoxanthine is described. The assay is based on the anodic oxidation of the product, uric acid, at a stationary carbon paste electrode. Metabolism was monitored as reaction proceeded by direct insertion of a three-electrode assembly into incubation mixtures, applying a potential and measuring current after a 7 sec controlled electrolysis. The method requires no sample preparation, nor utilization of external reagents, and is compared with the on-line spectrophotonetric analysis based on monitoring the appearance of uric acid detected as an increase in absorbance at 290 nm.     

The Alkylation of Mono- and Disaccharides Via an Initialising Electrochemical Step

Abstract

A new approach to the formation of ether derivatives of some mono- and di-saccharides by an initialising electrochemical step is described. With the exception of the nonreducing sucrose all compounds are protected at the anomeric center. In contrast to the general procedure we replaced the common bases by platinum as an electrode material with a small hydrogen overvoltage in aprotic media, such as DMF. In this way the hydroxyl groups are transformed to alcoholate anions with the generation of hydrogen. The reaction of these electrochemically generated anions with alkylating reagents such as allyl bromide, benzyl bromide and methyl iodide results in the formation of ether derivatives.     

Application of Periodate Oxidized Glucans to Biochemical Reactions

ABSTRACT

Periodate oxidation of glucans afforded a dialdehyde structure, which was highly reactive with various compounds containing amino groups. A covalent Schiff base linkage was readily formed at the alkaline pH of 8-9 and cyclodextrin dialdehyde gave both positively and negatively charged derivatives upon incubation with hexamethylenediamine and ?-aminocaproic acid, respectively. Binding of the amino group containing a fluorescent probe of ethylenediaminonaphthalene yielded fluorescent glycogen, which was hydrolyzed with Taka-amylase A. By gel filtration with a Bio-Gel P-2 column, hydrolyzed oligosaccharides containing a fluorescent probe were strongly retained to the column. Dextran dialdehyde was useful in producing a covalent linkage with trypsin under very mild conditions, and the enzyme-dextran complex formed was recovered in a high-molecular weight and active form. Thus, various glucan dialdehydes may serve as useful cross-linking reagents for enzymes.     

A recent approach for the synthesis of 1,2,4-triazine systems bearing and/or containing phosphorus atoms as donor-acceptor interaction and their biocidal affects: An overview

Abstract

This review reports the developed methods for the synthesis of polyfunctional 1,2,4-triazine systems bearing and/or containing phosphorus atoms as donor-acceptors interactions. Most of the synthetic methods depend on the interaction between an amino group of the side chain of 1,2,4-triazine with phosphorus reagents. The biological activities, i.e. their biocidal affects as antioxidants, antimicrobials, anti-inflammatory as well as molluscicidal agents against some snails are discussed.     

The synthesis,characterization, and electrochemistry of molecular cobaloxime/organocobaloxime: catalysts for cycloaddition of carbon dioxide and epoxides

The new cobaloxime (1), organocobaloxime (2), and their intramolecular hydrogen (O–H?O) bridges replaced by Cu(II)-containing multinuclear cobaloximes (3–10) were synthesized and characterized by elemental analysis, ¹H and ¹³C NMR spectra, FT-IR spectra, UV–vis spectra, LC-MS spectra, molar conductivity measurements, melting point measurements, and magnetic susceptibility measurements. Their electrochemical properties were investigated using cyclic voltammetric techniques in DMSO solution. The cobaloxime or organocobaloxime (1, 2) were used as precursors, replacing intramolecular O–H?O bridges, forming multinuclear complexes (3–10). Then, these compounds were used as homogeneous catalysts for cyclic carbonate synthesis from carbon dioxide (CO₂) and epoxides. In the catalytic experiments, dimethyl amino pyridine (DMAP) was used as co-catalyst, since DMAP was a more active base with higher yield compared to other Lewis bases. It is not necessary to use solvent according to catalytic test results, important in green chemistry.     

Synthesis of Polyfunctionally Substituted Pyrazolonaphthyridine,Pentaazanaphthalene, and Heptaazaphenanthrene Derivatives

6-aminopyrazolo[3,4-b]pyridine-5-carbonitrile (2) was used as a precursor for the synthesis of a variety of pyrazolo[3,4-b][1,8]naphthyridines (3, 4) and pentaazacyclopenta[b]naphthalenes (5–10, 13, 14) via the initial addition to either the cyano or amino group followed by cyclization. Also, a series of heptaazadicyclopenta[a,g]naphthalenes (15–17) and heptaazacyclopenta[b]phenanthrenes (18, 19) were obtained via the interaction of 4-(dibenzothiophen-2-yl)-1,5-dihydro-5-imino-3-methyl-1-phenyl-1,2,6,8,9-pentaazacyclopenta[b]naphthalen-6-ylamine (14) with different reagents. The structures of the synthesized compounds were established by elemental and spectral analyses.     

A Precautionary Note Regarding Derivatization of Secondary Amines with Dialkylacetals of Formamide Other Than the Diethyl Derivative

Abstract

We have extended our earlier work on alkylation of secondary amino compounds with dimethylformamide diethyl acetal to other alkyl acetals, such as dimethyl and dipropyl acetal. All the alkylating DMT-dialkyl acetal reagents tested gave only N-ethyl derivatives of the secondary amines. The reagent purity was tested by preparing the esters of carboxylic acids, where the appropriate alkyl (methyl or propyl) ester is obtained. It is concluded that all dimethylformamide dialkyl acetals yield a single N-ethyl derivative of secondary amine. The reaction mechanism is not understood.     

Traceless Approach for the Synthesis of 3,5-Disubstituted Thiohydantoins on Functionalized Ionic-Liquid Support

A traceless approach for the synthesis of 3,5-disubstituted thiohydantoins on a novel functionalized ionic-liquid support, 5, is described. Acylation of benzylamine functionalized ionic-liquid support with amino acids yielded ionic-liquid-supported amino acids, which reacted with isothiocyanates to afford ionic-liquid-supported thioureas. Following intramolecular cyclization cleavage from the ionic-liquid support by trifluoroacetic acid (TFA), the desired 3,5-disubstituted thiohydantoins were obtained in good yields and purities. The efficiency of this ionic-liquid-phase strategy facilitated isolation and analysis of intermediates and removal of excess reagents and by-products during the reaction process.