High throughput analysis of tryptophan metabolites in a complex matrix using capillary electrophoresis coupled to time-of-flight mass spectrometry

A capillary electrophoresis method for separation and detection with time-of-flight mass spectrometry is described for tryptophan metabolites in the kynurenic pathway. Tryptophan metabolites are usually difficult to detect with electrospray mass spectrometry since they have low surface activity and occur in low nanomolar to micromolar range in body fluids. Modification of the silica-wall with 1-(4-iodobutyl)4-aza-1-azoniabicyclo[2,2,2]octane iodide, also named M7C4I, has successfully been used to deactivate the fused silica wall and generate a stable reversed electroosmotic flow. Utilizing this advantage together with electrospray ionization time-of-flight mass spectrometry, which generates high resolution and fast acquisition monitoring of species, proved to be successful even for such a complex matrix like human cerebrospinal fluid.     

Rapid capillary electrophoresis time-of-flight mass spectrometry separations of peptides and proteins using a monoquaternarized piperazine compound (M7C4I) for capillary coatings

A monoquaternarized piperazine, 1-(4-iodobutyl) 4-aza-1-azoniabicyclo[2,2,2] octane iodide (M7C4I), has been evaluated as a surface derivatization reagent for CE in combination with TOF MS for the analysis of proteins, peptides, and protein digests. The M7C4I piperazine, at alkaline pH, forms a covalent bond via alkylation of the ionized silanols producing a cationic surface with a highly stable and reversed EOF. The obtained surface yields rapid separations (less than 5 min) of peptides and proteins at acidic pH with high separation efficiencies (up to 1.1 x 10(6) plates/m for peptides and up to 1.8 x 10(6) plates/m for proteins) and no observed bleeding of the coating reagent into the mass spectrometer. The simplicity of the coating procedure also enables fast (2 min) regeneration of the surface, if necessary. This is useful in the analysis of complex samples in order to prevent possible memory effects. The potential of using M7C4I-coated capillaries for MS analysis of complex samples is demonstrated by the separation of peptides, proteins, and protein digests. Even more, the spectacular thing in which large intact proteins with molecular masses over 0.5 MDa could be separated. The coating showed good ability to handle these large proteins with high efficiency and retained peak shape as demonstrated by separation of IgG(1) (150 kDa) and thyroglobulin (669 kDa).     

Sonochemical fluorination of heterocyclic nitro compounds with Selectfluor

Methine and methylene groups attached to a nitro function and heterocycle (and Ph for CH) were rapidly mono- or di-fluorinated by reaction with 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2,2,2]octane bis-tetrafluoroborate (Selectfluor) in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), preferably with ultrasonic irradiation.     

Sonochemical fluorination of heterocyclic nitro compounds with Selectfluor™ (F-TEDA-BF4)

CH and CH₂ groups attached to a heterocycle and a nitro function were rapidly mono- or difluorinated by reaction with 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2,2,2]octane bis-tetrafluoroborate (Selectfluor) in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), preferably with ultrasonic irradiation.     

Organic and inorganic di-cations for capillary silica coating and EOF modulation in CE: Example of application in PEG analysis

EOF measurements, by using 1,4-di-(4-aza-1-azonia-bicyclo[2.2.2]octane)butane diiodide, barium and strontium tetraborate as silica wall modifiers, are reported and, as an example of application, analysis of PEG (PEG 400-2000) polydisperse preparations in free solution CZE is shown. PEGs have been derivatized with phthalic anhydride so as to form singly or doubly charged derivatives with strong UV absorbance at 214 nm. Whereas separations in plain tetraborate buffer, pH 9.0, without any EOF control, did not lead to good resolution of all-size oligomers and suffered from long analysis times, excellent resolution of all oligomers up to 40 ethylene oxide (EO) units could be obtained under EOF control. Such EOF modulation was engendered by addition of 1 mM M7C4M7, a doubly charged organic cation able to stick tenaciously to the silica wall. Further modulation of EOF and silica surface modification could be achieved also by addition of inorganic cations, notably those of group II, whereas monovalent cations did not seem to affect much the EOF flux. Among the doubly charged cations investigated, Ca++, Mg++, Sr++ and Ba++, the latter did seem to offer best EOF control and reproducible runs. A judicious blend of M7C4M7 (0.33-1 mM range) with barium (10-20 mM range) allowed baseline resolution of all PEG oligomers investigated up to PEG 2000 and >40 EO units in length. In this last case, best results in terms of reproducibility and separation efficiency of the more heavy homologues were obtained using Li+ salt in small amounts.     

Mechanism of action of quaternary diamino quenchers in capillary zone electrophoresis

The synthesis of two novel amino compounds, able to quench and reverse the electroosmotic low (EOF) in capillary electrophoresis is here reported. These chemicals are derivatives of two previously described quaternarized piperazines, 1-(4-iodobutyl)-1,4-dimethylpiperazin-1-ium iodide (M1C4I) and 1-(4-iodobutyl)4-aza-1-azoniabicyclo[2.2.2] octane iodide (M7C4I), believed to bind covalently to the silica surface via alkylation of ionized silanols through their terminal, reactive iodine. The novel compounds, although unable to form a covalent bond, due to lack of the o-butyl iodine, are found to be very efficient in suppressing protein interaction with the wall and reversing the EOF. On the basis of their behavior in solution, the minimal structural motifs for strong binding of amino compounds to the silica wall have been derived and are thought to be: (i) the presence of two quaternary nitrogens in the molecule; (ii) a correct distance between said charged nitrogens, represented by a butyl chain (C(4)); (iii) an hydrophobic "decoration" of the molecules, consisting on a high CH(2)/N ratio (in the present case 8:1).     

Crystal Structures of Two Copper(I) Iodides: Chained [CuI(bta)] and Tetranuclear [(mdabco)<Subscript>2</Subscript>Cu<Subscript>4</Subscript>I<Subscript>6</Subscript>] (bta = Benzotriazole; mdabco = <Emphasis Type="Italic">N</Emphasis>-methyl-1,4-diazabicyclo[2,2,2]octane)

Abstract  

In methanol solutions, two types of organic N-donor ligands bta and dabco (bta = benzotriazole; dabco = 1,4-diazabicyclo[2,2,2]octane) were selected to react with CuI under the solvothermal conditions, creating two new copper(I) iodides as one-dimensional (1D) chained [CuI(bta)] 1 and tetranuclear [(mdabco)₂Cu₄I₆] (mdabco = N-methyl-1,4-diazabicyclo[2,2,2]octane). Note that mdabco derived from the solvothermal in situ alkylation reaction between dabco and methanol solvent. The photoluminescence analysis revealed that compound 2 is a potential fluorescence material with maximum emission at 506 nm.     

Unprecedented cage-carbon to cage-boron NMe(3) transfer in a monocarbon Molybdenacarborane

The reagent Li(2)[7-NMe(3)-nido-7-CB(10)H(10)] reacts with [Mo(CO)(3)(NCMe)(3)] in THF-NCMe (THF = tetrahydrofuran) to give a molybdenacarborane intermediate which, upon oxidation by CH(2)[double bond]CHCH(2)Br or I(2) and then addition of [N(PPh(3))(2)]Cl, gives the salts [N(PPh(3))(2)][2,2,2-(CO)(3)-2-X-3-NMe(3)-closo-2,1-MoCB(10)H(10)] (X = Br (1) or I (2)). During the reaction, the cage-bound NMe(3) substituent is transferred from the cage-carbon atom to an adjacent cage-boron atom, a feature established spectroscopically in 1 and 2, and by X-ray diffraction studies on several of their derivatives. When [Rh(NCMe)(3)(eta(5)-C(5)Me(5))][BF(4)](2) is used as the oxidizing agent, the trimetallic compound [2,2,2-(CO)(3)-7-mu-H-2,7,11-[Rh(2)(mu-CO)(eta(5)-C(5)Me(5))(2)]-closo-2,1-MoCB(10)H(9)] (10) is formed, the NMe(3) group being lost. Reaction of 1 in CH(2)Cl(2) with Tl[PF(6)] in the presence of donor ligands L affords neutral zwitterionic compounds [2,2,2-(CO)(3)-2-L-3-NMe(3)-closo-2,1-MoCB(10)H(10)] for L = PPh(3) (4) or CNBu(t) (5), and [2-Bu(t)C[triple bond]CH-2,2-(CO)(2)-3-NMe(3)-closo-2,1-MoCB(10)H(10)] (6) when L = Bu(t)C[triple bond]CH. When 1 is treated with CNBu(t) and X(2), the metal center is oxidized, and in the products obtained, [2,2,2,2-(CNBu(t))(4)-2-Br-3-X-closo-2,1-MoCB(10)H(10)] (X = Br (7), I (8)), the B-NMe(3) bond is replaced by B-X. In contrast, treatment of 2 with I(2) and cyclo-1,4-S(2)(CH(2))(4) in CH(2)Cl(2) results in oxidative substitution of the cluster and retention of the NMe(3) group, giving [2,2,2-(CO)(3)-2-I-3-NMe(3)-6-[cyclo-1,4-S(2)(CH(2))(4)]-closo-2,1-MoCB(10)H(9)] (9). The unique structural features of the new compounds were confirmed by single-crystal X-ray diffraction studies upon 6, 7, 9 and 10.     

DABCO,A REAGENT FOR DEPROTECTION OF BENZYLIC TRIMETHYLSILYL ETHERS UNDER MICROWAVE IRRADIATION IN A SOLVENTLESS SYSTEM

Deprotection of trimethylsilyl ethers of benzylic alcohols to the corresponding alcohols using 1,4-diazobicyclo[2,2,2]octane (DABCO) under microwave irradiation under solvent-free conditions is reported.     

Confirmation of the E and Z attribution to the isomers of 3-ethylidene-1-azabicyco-[2,2,2]octane by CMR spectroscopy

CMR spectra of the following bicyclo[2,2,2]octane compounds were measured: 1-azabicyclo[2,2,2]octan-3-one ( 3 ), 2-azabicyclo[2,2,2]octan-3-one ( 5 ), bicyclo[2,2,2]octaone ( 4 ), 3-ethyl-1-azabicyclo[2,2,2]oct-2-ene ( 6 ) and of the Z and E isomers of 3-ethylidene-1-azabicyclo-[2,2,2]octane ( 1 and 2 ). The attribution of the signals and confirmation of the Z and E configuration of isomers ( 1 ) and ( 2 ) is described.     

Pentacobalt(II) cluster based pcu network exhibits both magnetic slow-relaxation and hysteresis behaviour

A pentacobalt(II) cluster based 3D pcu network, [Co(5)(μ(3)-OH)(2)(bpdc)(4)(dabco)(H(2)O)(2)] (bpdc = benzophenone-2,4'-dicarboxylate and dabco = 1,4-diazabicyclo[2,2,2] octane), exhibiting both slow magnetic relaxation and hysteresis behavior, has been hydrothermally synthesized.     

Synthesis and Characterization of a Novel Zeolite CJS-4

A novel zeolite, denoted as CJS-4, has been synthesized from nonalkaline medium by using 4,4'-trimethylenebis(1-methylpiperidine) or 1,4-diazoniabicyclo(2,2,2) octane as template agent, respectively. The precursors were characterized by means of powder X-ray diffraction, scanning electron microscopy, thermal analysis, gas adsorption and high resolution solid state NMR of 13C and 29Si.     

一维链状卤化亚铜化合物的溶剂热原位合成、 结构及性质

采用溶剂热原位反应合成了一例具有一维铜卤链结构的化合物(C₁₀H₂₂N₂)₃[Cu₉I₁₄Br](C₁₀H₂₂N₂=N,N'-二乙基三乙烯二胺阳离子). 利用X射线单晶衍射、 元素分析、 粉末X射线衍射及红外光谱等测试手段对化合物进行了表征. 测试结果表明, 化合物属于单斜晶系, C2/c空间群, a=2.6233(5)nm, b=1.6299(3)nm, c=1.6707(3)nm, β=117.31(3)°, V=6.347(2) nm³. 化合物的结构由一维的铜卤链和有机模板剂构成, 其中有机模板剂是通过三乙烯二胺和乙醇烷基化反应得到的有机季铵盐阳离子. 该化合物在室温下表现出较好的光致发光性质.     

Kinetics of the Protonation of Macrocyclic Amines in the Presence of Monovalent Cations in Aqueous Solution

Abstract

For macrocyclic bases such as: 1-aza-15-crown-5 (N15C5),1,4,10-trioxa-7,13-diazacyclopentadecan (21), 1,7,10,16-tetraoxa-4,13-diazacyclooctadecan (22) and 1, 4, 7, 13, 16-pentaoxa-10, 19-diazacycloheneicosane (23), the kinetics of deprotonation and protonation reactions in the presence of monovalent cations was studied using the temperature jump technique. For the sake of comparison, the measurements were also performed for 1,4-diazabicyclo[2,2,2]octane (DABCO) base, which does not form complexes with monovalent cations. The monovalent cations affect the temperature dependence of the kinetic parameters of deprotonation. They also affect the activation parameters, which is shown by a distribution of ΔH≠ and ΔS≠ values, but do not influence the value of ΔG≠.     

1,4-Diaza-bicyclo[2,2,2]octane as a Novel and Efficient Catalyst for the Synthesis of 3,4,6-Trisubstituted 2-Pyridone Derivatives

3,4,6‐Trisubstituted 2‐pyridone derivatives have been synthesized in good to excellent yields through a condensation reaction of various 1,3‐diketones with amides in the presence of 1,4‐Diaza‐bicyclo[2,2,2]octane (DABCO) at reflux temperature.     

One pot synthesis of side chain fluorinated heterocyclic compounds by microwave irradiation

2- Or 4-Difluoronitromethyl and 2- or 4-fluoronitrobenzyl substituted pyridines, quinolines, phenantheridine, benzothiazol and benzoxazol were synthesized by reaction of the corresponding nitro compounds in the presence of 1-chloromethyl-4-fluoro-1,4-diazoiabicyclo[2,2,2]octane bis(tetrafluoroborate) (Select-Fluor) and ammonium acetate as a base under microwave irradiation. This method is very efficient and the yields were significantly improved in comparison to the previous reports.     

Selectfluor™ promoted synthesis of 9-aryl-1,8-dioxooctahydroxanthane derivatives under solvent-free conditions

A novel and efficient procedure for the synthesis of 1,8-dioxo-octahydro-xanthenes through one-pot condensation of 5,5- dimethyl-1,3-cyclohexadione with aryl aldehydes in the presence of selectfluor? [1-(chloromethyl)-4-fluoro-1,4- diazoniabicyclo[2,2,2]octane bis(tetrafluoroborate) as catalyst under solvent free conditions was applied. It demonstrated several advantages such as good yields of products, simple operation, convenient separation, and inexpensive catalyst.     

Conformation Analysis and Thermodynamics of Binding Behavior of DABCO to p/p type Dimeric Porphyrin Hosts

Covalently linked metalloporphyrin dimers have attracted considerably interest among chemists as models for metalloenzymes, which derive from their remarkable electron, energy transfer and special conformation properties1,2. Metalloporphyrins with large cavities have been designed and assembled with the idea of creating multisite complexing hosts incorporating functionalized subunits for binding organic substrates and transition metals so as to mimic metalloenzymes, as well as supermolecular ph…     

Convenient method for preparation of aryl sulfinates from arenes and DABSO as the SO2 surrogates

A safe and efficient protocol for the synthesis of aryl sulfinates from arenes and 1,4-diazabicyclo[2,2,2]octane bis(sulfur dioxide) (DABSO) under mild conditions is described. Through in situ infrared spectroscopic studies, a plausible mechanism for the sulfination reaction is proposed as well.     

Kinetic separation of hexane isomers by fixed-bed adsorption with a microporous metal-organic framework

A three-dimensional microporous metal-organic framework Zn(BDC)(Dabco)0.5 (BDC = 1,4-benzenedicarboxylate, Dabco = 1,4-diazabicyclo [2,2,2]octane), having two types of intersecting pores to encapsulate linear hexane and to block branched hexanes, and thus exhibiting highly selective sorption with respect to n-hexane, has been successfully applied to the kinetic separation of hexane isomers by fixed-bed adsorption.