Dimethylamine Group Research Articles

Reactive trityl derivatives: stabilised carbocation mass-tags for life sciences applications

The rational design of novel triarylmethyl (trityl)-based mass tags (MT) for mass-spectrometric (MS) applications is described. We propose a "pK(R+) rule" to correlate the stability of trityl carbocations with their MS performance: trityls with higher pK(R+) values ionise and desorb better. Trityl blocks were synthesised that have high pK(R+) values and are stable in conditions of MS analysis; these MTs can be ionised by matrix as well as irradiation with a 337 nm nitrogen laser. (13)C-Labelled tags were prepared for MS quantitation applications. Moreover, the tags were equipped with a variety of functional groups allowing conjugation with different functionalities within (bio)molecules to enhance the MS characteristics of the latter. The MS behaviour of model polycationic trityl compounds with and without the matrix was studied to reveal that poly-trityl clusters are always singly charged under the (MA)LDI-TOF conditions. Several peptide-trityl conjugates were prepared and comparisons revealed a beneficial effect of trityl tags on the conjugate detection in MS. Trityl compounds containing para-methoxy- and dimethylamine groups, as well as a xanthene fragment, showed considerable enhancement in MS detection of model peptides; thus they are promising tools for proteomic applications. Dimethoxytrityl derivatives allow one to distinguish between Arg- and Lys-containing peptides. Maleimido trityl derivatives are suitable for the efficient derivatisation of thiol-containing peptides in pyridine.

11C]-dimethylamine as a labeling agent for PET biomarkers

The dimethylamine functional group is a common component of the chemical structure of numerous drugs. The most commonly used synthetic route for carbon-11 labeled radiopharmaceuticals which contain the dimethylamine group is via C-11 methylation of the monomethyl amine precursors. Here we describe the radiosynthesis of [ 11C]dimethylamine ( 1) and its application in the direct labeling of several positron emission tomography (PET) imaging agents by-passing the preparation of the monomethyl amine precursors.

New solvated form of the antibiotic azithromycin. Clues about the role of the water retained inside the crystal

The structure of a new semihydrate solvated form of the antibiotic azithromycin is reported. The new form was obtained by partial dehydration of the crystal of the monohydrate-i-PrOH, when the sample was left in laboratory conditions (22–25 °C, 55–65% relative humidity) over a long period of time (about 40 months). The new semihydrate solvate form retains the crystalline structure of the monohydrate (unit cell parameters and space group) but shows changes in the position of the hydrogen atoms of some OH groups of the azithromycin molecules, leading to a new and different hydrogen bonding network. Moreover, in one of the two azithromycin molecules in the asymmetric unit (the one labelled as “b”), the dimethyl amine group (in the desosamine sugar) shows a significant positional change. This fact provides information about the role of the solvent in the building of the solvated forms of the azithromycin drug, and allows the mobility of this group to be associated with an inversion operation and not a rotation.

DFT-PCM STUDIES OF THE SOLVENT EFFECTS ON THE ABSORPTION PROPERTIES OF DCM

In this paper, we have performed the optimized structures of the red emitting material, 4-(dicyanomethylene)-2-methyl-6-[p-(dimethyl amino) styryl]-4H-pyran (DCM), with different polarity solvent environments by using the density functional theory (DFT) method, B3LYP/6-31G*. The time-dependent density functional theory (TD-DFT) and the polarizable continuum model (PCM) have been used to obtain the optical properties in the solvent environment. It has been observed that when the solvent polarity increases, the DCM molecule exhibits the red shift in the maximum absorption wavelength [Formula: see text] and enhances the oscillator strength (f). The solvent polarity also enhances the electron transfer ability from the electron-donating dimethylamine group (-N(CH3)2) to the electron-withdrawing =C(CN)2group. The S0→ S1transition of DCM is found to be π–π*. The maximum absorption wavelengths [Formula: see text] of different solvent environments are found to be consistent with the reported experimental results.

PH-Responsive Random Copolymer Films with Amine Side Chains

We have designed pH-responsive copolymer films that consist of polymethylene (PM) with dilute randomly distributed side chains terminated with dimethylamine groups. The films are grown on gold surfaces by (1) exposure to an ether solution of diazomethane and ethyl diazoacetate to produce a random copolymer Au-[(CH2)A-(CHCO2Et)B] (denoted as PM-CO2Et, A ≫ B), (2) hydrolysis of the ester groups to carboxylic acids (PM-CO2H), (3) complete conversion of the acids to acid chlorides (PM-COCl), and (4) quantitative reaction of the acid chlorides with N,N-dimethylethylenediamine (DMEDA) to yield a film (PM-CONHR, R represents −-CH2CH2N(CH3)2) with amide-linked, amine-terminated side groups that are pH active. The effect of polymer composition on pH response was investigated by electrochemical impedance spectroscopy (EIS). PM-CONHR films are more hydrophilic in their uncharged state than PM-CO2H films and thereby exhibit lower resistance against ion transfer. When the pH is decreased, the amine groups become protonated or charged, dramatically increasing their hydrophilicity and reducing the resistance of the film against ion transfer by around 2 orders of magnitude over the pH range of 7 to 4. In contrast, PM-CO2H films become protonated or neutralized as the pH is decreased and exhibit a 5 order of magnitude increase in resistance over a similar range of pH. The hydrophobicity of the PM-CONHR films can be enhanced by capping the acid chloride groups with a mixture of DMEDA and n-butylamine to yield a film with some pH inert groups that boost film resistance in the uncharged state and increase the magnitude of the change in film resistance. The resistance of the film against ion transfer correlates well with the hydrophobicity of its dilute side chain component, as quantified by the octanol−water partition coefficient (Kow).

Chloroformamidinium Salts: Efficient Reagents for Preparation of 2‐Aminobenzoimidazole, 2‐Aminobenzoxazole, and 2‐Aminobenzothiazole Derivatives.

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Chloroformamidinium salts: Efficient reagents for preparation of 2‐aminobenzoimidazole, 2‐aminobenzoxazole, and 2‐aminobenzothiazole derivatives

Abstractmagnified imageA Reaction involving chloroformamidinium salts (TCFH 1a, BTCFH 1b, DmCFH 1c, DmPCFH 1d, BPCFH 1e) and 2‐aminophenol 9a, benzene‐1,2‐diamine 9b, and 2‐aminothiophenol 9c afforded 2‐aminobenzoxazole 13, 2‐aminobenzoimidazole 14, and 2‐aminobenzothiazole 15 derivatives, respectively as major products, due to the in situ heterocyclization with dimethylamine acting as the better leaving group. Attempts for preparation of 13‐15 from the reaction of N,N‐dimethyl carbomyl chloride 16 with 2‐aminophenol 9a, benzene‐1,2‐diamine 9b, and 2‐aminothiophenol 9c were unsuccessful, and gave the unexpected products benzoxazol‐2‐ol 18a, benzoimidazol‐2‐one 18b, and S‐(2‐amino‐phenyl) N,N‐dimethylthiocarbamate 19 respectively. On the other hand reaction of chloroformamidinium salts 1a‐e with 3‐benzyl‐2‐hydrazinoquinoxaline 3 and 1‐hydrazinophthalazine hydrochloride 4 in the presence of triethylamine as a base, afforded the [1,2,4]triazolo derivatives 6 and 7 respectively in good yield and purity. These triazole derivatives were formed due to the strong tendency towards heterocyclization and substitution of dimethylamine group as a better leaving group.

A New Amine-Modified Hypercrosslinked Polymeric Adsorbent for Removing Phenolic Compounds from Aqueous Solutions

A new amine-modified hypercrosslinked polymeric resin, AH-6, for the removal of phenolic compounds from their aqueous solutions was prepared by introducing dimethylamine groups onto the matrix of the conventional hypercrosslinked polymeric adsorbent NDA100. The adsorption of four phenolic compounds, i.e. phenol, p-cresol, p-chlorophenol and p-nitrophenol, onto the NDA100 resin with or without amine modification was investigated using the commercial styrene-type weakly alkaline resin D301 as a reference. The Freundlich isotherm equation was employed to fit the adsorption process.The aminated hypercrosslinked polymeric resin exhibited a higher adsorption capacity towards phenol and p-chlorophenol than both the unmodified hypercrosslinked polymeric resin NDA100 and the styrene-type weakly alkaline resin D301. To interpret the adsorption behaviour of the AH-6 resin, a dual function interaction mechanism involving π–π interaction between the AH-6 resin matrix and the benzene ring of the adsorbate and hydrogen-...

Structural characterization of two novel potential anticholinesterasic agents

Two novel compounds with possible anticholinesterase activity have been synthesized containing a carbamate and a dimethylamine group in 1,2-positions of a cyclohexane ring ( cis and trans isomers). Conformer populations were established by a combination of NMR 1H coupling constant analysis and DFT (B3LYP/6-311+G(d,p)) calculations. 13C chemical shifts were calculated in order to confirm signal attributions. The cis isomer adopts a conformation in which the carbamate group lies at the axial position (>99%), whereas the trans isomer adopts a diequatorial arrangement (98%). These preferences have been explained in terms of syn-1,3-diaxial interactions of the individual groups.

Synthesis and Properties of Amphiphilic Hyperbranched Poly(dimethylsiloxane) Possessing Hydrophilic Terminal Group

The amphiphilic hyperbranched poly(dimethylsiloxane) (HPDMS) bearing dimethylamine groups on the terminal position was synthesized and characterized. The obtained polymer exhibited low viscosity, and good solubility in ether, THF, and acidic aqueous solution. In the acidic aqueous polymer solution, UV-vis absorption and photo luminescence of water-insoluble chromic compounds such as diphenylhexatriene were measured in order to investigate solvating power of hyperbranched poly(dimethylsiloxane)s. It has turned out from the UV absorbance data that a HPDMS solubilized about five molecules of 1,6-diphenylhexatriene.

Characterization of [ReO(Tetramethylthiourea)4](PF6)3 in Solution: Electrochemical, NMR and Ligand Substitution Studies

The complex [ReO(Me4tu)4]3+, with Me4tu = tetramethylthiourea, is characterized in nonaqueous media. Its structure is studied in acetonitrile solution by 1H and 13C NMR and its electrochemical behavior in the same solvent is analyzed by means of cyclic voltamperometric measurements. Heteronuclear correlation and variable temperature NMR experiments suggest that the complex ion shows a similar structure in solution and in the solid state. At low temperatures (below 0°C) free rotation of the dimethylamine groups around the thiocarbonyl carbon-nitrogen bond is restricted and the dissolved complex adopts the rigid structure observed in the solid state. Cyclic voltamperometric results suggest that the redox behavior of this compound can be explained through an ErCiEr mechanism (a chemical reaction coupled between two electron-transfer reactions). An initial one electron reduction of the complex from Re(V) to Re(IV) followed by an irreversible chemical reaction, leads to a new electroactive species of Re(IV)*, which is reduced to Re(III). The ability of [ReO(Me4tu)4](PF6)3 to serve as a precursor for other Re(V) complexes by ligand substitution is established, in acetone solution, with different kinds of incoming ligands: diethyldithiocarbamate (Et2dtc), ethylenediamine (en) and pyridine (py). The previously known complexes [Rev 2O3(Et2dtc)4], [ReVO2(en)2](PF6) and [ReVO2(py)4](PF6) are easily synthesized under mild conditions with high yields.

Preparation of a copolymer of methyl methacrylate and 2-(dimethylamino)ethyl methacrylate with pendant 4-benzyloxy-2,2,6,6-tetramethyl-1-piperidinyloxy and its initiation of the graft polymerization of styrene by a controlled radical mechanism

The macroinitiator of a copolymer (PMD BTM ) of methyl methacrylate (MMA) and 2-(dimethylamino)ethyl methacrylate (DAMA) with 4-benzyloxy-2,2,6,6-tetramethyl-1-piperidinyloxy (BTEMPO) pendant groups was prepared by the photochemical reaction of tertiary amine groups of the copolymer with benzophenone in the presence of BTEMPO. The radical copolymerization of MMA and DAMA was carried out first with azo-bis-isobutyronitrile (AIBN) as an initiator; then, the dimethylamine groups of the copolymer constituted a charge-transfer complex with benzophenone under UV irradiation, and the methylene of ternary amine and diphenyl methanol radicals were produced. The former was capped by BTEMPO, and the nitroxide (BTEMPO) was attached to the polymeric backbone. The amount of pendant BTEMPO on PMD BTM was measured by 1 H NMR. PMD BTM initiated the graft polymerization of styrene via a controlled radical mechanism, and the molecular weight of the PMD-g-polystyrene increased with the polymerization time.

Effect of the substituents on the solvatochromic behaviour of benzimidazole-based betaine dyes

The solvatochromic effect was studied in the family of benzimidazole-based zwitterionic betaine dye molecules. The ground-state dipole moments of the molecules were determined from dielectric measurements; depending on the substituents, they ranged from ca. 6 to over 13 Debye units. A pronounced shift of the lowest-lying absorption band was found depending on the polarity of solvents: the betaine dyes substituted with the dimethylamine group in the terminal phenyl ring exhibit a bathochromic shift whereas the dye unsubstituted or substituted with the nitro group exhibit a hypsochromic shift. The comparison of the experimental results with the quantum-chemical calculations seems to indicate that the reason for this difference rests in enhanced probability of specific interactions in the former betaines (possible formation of hydrogen bond to the imidazole nitrogen).

Reaction of dimethylamine with 4,5-dichloro-4-cyclopenten- 1,3-dione: X-ray diffraction structure and cyclic voltammetric data for {ie-1}

Dimethylamine reacts with 4,5-dichloro-4-cyclopenten-1,3-dione (1) to give the monosubstituted amine compound 4-dimethylamino-5-chloro-4-cyclopenten-1,3-dione (2) as the sole isolable product. Attempts to replace the remaining chlorine group in 2 by a second dimethylamine group have been unsuccessful. Compound 2 has been isolated and characterized in solution by IR and NMR ( 1 H and 13 C) spectroscopy, and the solid-state structure for ClC=C(NMe 2 )C(O)CH 2 C(O) has been determined by X-ray diffraction analysis. ClC=C(NMe 2 )C(O)CH 2 (O) crystallizes in the triclinic space group P1, a = 7.2224(4) A, b = 7.9008(6) A, c = 8.3284(8) A, α = 63.803(6)°, β = 67.401(6)], γ = 87.889(5)°, V = 388.59(6) A 3 , Z = 2, d calc = 1.484 g.cm -3 ; R = 0.0422, R w = 0.0450 for 1552 observed reflections with l > 3σ(l). The cyclic voltammetric behavior of ClC=C(NMe 2 )C(O)CH 2 C(O) has been explored at a platinum electrode in CH 2 Cl 2 and THF, and the orbital composition of the HOMO and LUMO in 2 was established by extended Huckel molecular orbital calculations on the model compound ClC=C(NH 2 )C(O)CH 2 C(O). The cyclic voltammetry data of 2 is contrasted with the known diphosphine compound 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd; 3) and predictions concerning the ability of ClC=C(NMe 2 )C(O)CH 2 C(O) to function as an electron reservoir in organometallic compounds is discussed.

Association behavior of linear ?-functionalized polybutadienes in cyclohexane

The dilute solution properties of linear polybutadienes with dimethylamine and zwitterionic end groups were studied by membrane osmometry (MO), low-angle laser light scattering (LALLS), viscometry, and dynamic light scattering (DLS) in cyclohexane. The polymers were prepared by anionic polymerization, under high vacuum conditions using [3-(dimethylamino)propyl]lithium as initiator. The dimethylamine groups were converted to zwitterions by reaction with cyclopropane sultone. No evidence of association was found for the amine-capped polymers, whereas the zwitterionic samples exhibited strong association in cyclohexane. The degrees of association increase by decreasing molecular weight of the base polymer due to the excluded volume repulsions. These aggregation numbers are of the same order as those found for ω-functionalized polyisoprenes, with the same polar groups in the same solvent. The hydrodynamic properties, measured by viscometry and dynamic light scattering, supported the conclusions drawn by LALLS and provide strong evidence that the aggregates behave hydrodynamically as star polymers. Comparison with theoretical models shows that the association behavior is best described by the linear head packing model.

Scope and limitations of 1,1‐diphenylethylene chemistry in anionic polymer synthesis

AbstractThe scope and limitations of the addition reactions of simple and polymeric organolithium compounds with substituted 1,1‐diarylethylenes to prepare in chain‐ and chain‐end functionalized polymers is presented. The application of this general living functionalization reaction for the preparation of ω‐functionalized polymers is illustrated for hydroxyl, carboxyl, dimethylamine, and primary amine groups, as well as for the fluorescent naphthalene and pyrene labels. The use of this chemistry to prepare functionalized initiators is described, as well as the copolymerization of substituted 1,1‐diphenylethylenes with monomers to prepare in‐chain functionalized polymers with alternating structures.

Circumvention of adriamycin resistance by dipyridamole analogues: A structure‐activity relationship study

Dipyridamole restores sensitivity to Adriamycin (ADR) in drug-resistant cells. In an effort to elucidate the relationship between activity and chemical structure of dipyridamole, the ability to enhance the growth inhibitory effect of ADR, in multidrug-resistant (MDR) P388 murine leukemia cells, was determined for 43 derivatives and related compounds. Since both substituted pyrimidopyrimidines and pteridines enhanced the growth-inhibitory effect of ADR in drug resistant cells, the core skeleton may not be directly involved and rather serve as a carrier for the substituents connected with this activity. The exact positions of the active substituents on the core skeleton did not seem to be critical for exertion of the activity. Activity was dependent on the presence of 3 tertiary amine groups. However, not all tertiary amines showed the same potency which might be related to the degree of basicity and/or the spatial structure of these groups. The most active derivatives carried piperidine and pyrrolidine groups while derivatives with thiomorpholine, 3-hydroxypiperidine or dimethylamine groups had low activity. Activity was also dependent on the presence of a substituent with partial electronegative charges as found in a diethanolamine group. However, this function could be carried out, with even higher efficiency, by a substituent containing 6 pi electrons.