Isopentyl Groups Research Articles

Structural effects of benzene-centered tripodal diglycolamides on extraction of trivalent f-cations into a room temperature ionic liquid

A series of three benzene functionalized tripodal diglycolamide (DGA) extractants (abbreviated as Bz-T-DGA, and termed as LI, LII and LIII) were studied for their extraction abilities for Eu3+ and Am3+ ions. Extraction efficiencies of these ligands are distinctly dependent on: (i) the nature of alkyl substituents on amidic N atoms of DGA, (ii) alkyl chain length that connects the DGA moeties with the benzene ring, and (iii) the medium of extraction. Substitution of protons with iso-pentyl groups on DGA nitrogen atoms enhanced the ligand extraction efficiency many folds. At the same time, increasing the spacer atoms between the benzene platform and the DGA units reduced the ligand extraction efficiency. The distribution ratio of Eu3+ was higher than that of Am3+ with all the three ligands, but the separation factor between the two elements was less than 2. Solvent extraction mechanism was entirely different when the organic solvent changed from n-dodecane (a molecular solvent) to ionic liquid. DFT calculations revealed that the solvent extraction abilities of these ligands were primarily goverened by their complexation abilities for trivalent f-cations.

Development of isoquinolinone derivatives as immunoproteasome inhibitors

The inhibition of immunoproteasome is considered nowadays a promising strategy for the treatment of hematologic malignancies. In this paper we report the design, synthesis, and biological evaluation as immunoproteasome inhibitors of a new series of isoquinolinone derivatives characterized by a (E)-prop-1-ene fragment that connects the heterocycle to a distal amide functionality. Among all the synthesized compounds, we identified an inhibitor with Ki values in the low micromolar or submicromolar range towards the chymotrypsin-like activities of both proteasome and immunoproteasome (β5c, β5i and β1i subunits). Molecular modeling studies suggest that the most potent compound of the series may act a single-site binder. In particular, through its isopentyl group, it might dock into P1 site in the case of the β1i catalytic subunit, while in the case of β5c and β5i subunits, the P3 site might be the preferred binding site.

Highly efficient uptake of neptunium from acidic feeds using two solid phase extraction resins containing diglycolamide-functionalized calix[4]arene ligands

Two solid phase extraction resins (SPER) were prepared by impregnating solutions of two diglycolamide-functionalized calix[4]arenes in 10% isodecanol in n-dodecane into Chromosorb W, as the stationary phase. While SPER-I contained n-propyl functionalized calix[4]arene, SPER-II contained the calix[4]arene with isopentyl groups at the carboxamide nitrogen atoms. The SPERs were characterized by SEM, TGA, FTIR, etc. and were used for the batch uptake of neptunium(IV) from nitric acid feed solutions. While the uptake of Np(IV) was extremely high with SPER-I (Kd: 47,544 at 3 M nitric acid, ca. 8% extractant loading), SPER-II displayed a significantly lower extraction efficiency (Kd: 13,724 under identical conditions) as indicated by the batch uptake studies. Sorption isotherm studies were carried out which indicated good fitting to the Langmuir model suggesting uptake conforming to monolayer sorption. Fitting to the D-R isotherm model conformed to a chemisorption model. Column studies were also carried out and the elution profiles, obtained with solutions of oxalic acid and nitric acid indicated very sharp peaks suggesting that the column can be used for the separation of Np(IV) from acidic radioactive feeds.

Chemical and morphological effects of blended sulfonated poly(styrene‐isobutylene‐styrene) and isopentylamine for direct methanol fuel cell applications

AbstractIn this study, blend membranes based on a combination of sulfonated poly (styrene‐isobutylene‐styrene) (SIBS) with isopentylamine (IPA) were synthetized as potential candidates for direct methanol fuel cell (DMFC) applications. The impact of sulfonation level (57–93 mol%) and percentage of IPA incorporation (1, 3, and 5 wt%) were analyzed via different properties of the resulting membrane. FTIR analysis showed that IPA was successfully incorporated into the sulfonated polymer matrix and also confirmed the interaction between the sulfonic and amine groups. This interaction generates significant morphological changes in the nanostructure of the membranes that are evident through results of small angle x‐ray scattering and atomic force microscopy analysis. Proton conductivity and methanol permeability of the membranes were also analyzed. Proton conductivity was significantly enhanced with the incorporation of IPA at an optimum loading, creating additional paths for the conduction of protons through the membrane. It was also sensitive to the morphological changes produced after the IPA incorporation and the interconnection between the ionic domains. Methanol permeability increased slightly due to the additional water domains and the inability of the isopentyl groups of IPA to block the free‐volume in the membrane. Despite this, the selectivity (proton conductivity over methanol permeability) of the membranes was comparable to the state‐of‐the‐art Nafion®, especially at an optimum IPA incorporation of 3 wt%.

ISOMERS OF 3-CHLORO-N,N,N-TRIS(3-METHYLBUTYL)PROP-2-EN-1-AMMINIUM CHLORIDE AS COMPLEX OIL AND GAS FIELD REAGENTS WITH ANTIHYDRATE, ANTICORROSIVE AND BACTERICIDAL ACTION

One of the most promising classes of low-dosage hydrate inhibitors is anti-agglomerants, which are favorably characterized by high efficacy at very low working concentrations (0.1-0.5%). We have investigated the possibility of creating new anti-agglomerants with enhanced anticorrosive and bactericidal properties based on the quaternization of tris(3-methylbutyl)amine with (E)- and (Z)-1,3-dichloropropene isomers. It is well known that compounds with a 3-chloroprop-2-enyl fragment have a pronounced anticorrosive and bactericidal action. Thus, the presence in the quaternization products of isopentyl groups and 3-chloroprop-2-enyl fragments that are optimal for preventing agglomeration of the gas hydrates can contribute to the complex antihydrate, anticorrosive and bactericidal activity of these compounds. An attempt to conduct the alkylation of tris(3-methylbutyl)amine with (E)-1,3-dichloropropene in standard solvent – boiling ethanol for 3 days leads to a low yield of the target quaternary salt. Using chromatography-mass spectrometry, it was established that there are significant amounts of by-products in the reaction mixture, which are formed as a result of various nucleophilic substitutions and elimination reactions. Alkylation of tris(3-methylbutyl)amine in boiling acetonitrile proceeds faster and more selectively in 80% yield of (E)-3-chloro-N,N,N-tris(3-methylbutyl)prop-2-en-1-amminium chloride in 20 h. A quaternization with (Z)-1,3-dichlopropene under the same conditions gives an isomeric quaternary salt with a similar yield. The alkylation of tris(3-methylbutyl)amine with isomers of 1,3-dichloropropene proceeds without allyl rearrangement and with full retention of the configuration of the chlorovinyl fragment. The structure and purity of the obtained compounds was unambiguously confirmed by NMR spectroscopy data. Tests in rocking cells using tetrahydrofuran-water model systems (forming the structure sII similar to natural gas hydrates), gravimetric and microbiological methods showed high antihydrate, anticorrosive and bactericidal efficiency of the obtained compounds in concentrations of 0.5%.

Low Valent Magnesium Chemistry with a Super Bulky β‐Diketiminate Ligand

AbstractThe steric bulk of the well‐known DIPPBDI ligand (CH[C(CH3)N‐DIPP]2, DIPP=2,6‐diisopropylphenyl) was increased by replacing isopropyl for isopentyl groups. This very bulky DIPePBDI ligand could not stabilize the radical species (DIPePBDI)Mg.: reduction of (DIPePBDI)MgI with Na gave (DIPePBDI)2Mg2 with a rather long Mg‐Mg bond of 3.0513(8) Å. Addition of TMEDA prior to reduction gave complex (DIPePBDI)2Mg2(C6H6), which could also be obtained as its THF adduct. It is speculated that combination of a bulky spectator ligand and TMEDA prevents dimerization of the intermediate MgI radical, which then reacts with the benzene solvent. Complex (DIPePBDI)2Mg2(C6H6), which formally contains the anti‐aromatic anion C6H62−, reacted with tBuOH as a Brønsted base to 1,3‐ and 1,4‐cyclohexadiene and with H2 as a two electron donor to (DIPePBDI)2Mg2H2 and C6H6. It also reductively cleaved the C−F bond in fluorobenzene and gave (DIPePBDI)MgPh, (DIPePBDI)MgF, and C6H6.

Low Valent Magnesium Chemistry with a Super Bulky β-Diketiminate Ligand.

The steric bulk of the well-known DIPP BDI ligand (CH[C(CH3 )N-DIPP]2 , DIPP=2,6-diisopropylphenyl) was increased by replacing isopropyl for isopentyl groups. This very bulky DIPeP BDI ligand could not stabilize the radical species (DIPeP BDI)Mg. : reduction of (DIPeP BDI)MgI with Na gave (DIPeP BDI)2 Mg2 with a rather long Mg-Mg bond of 3.0513(8) Å. Addition of TMEDA prior to reduction gave complex (DIPeP BDI)2 Mg2 (C6 H6 ), which could also be obtained as its THF adduct. It is speculated that combination of a bulky spectator ligand and TMEDA prevents dimerization of the intermediate MgI radical, which then reacts with the benzene solvent. Complex (DIPeP BDI)2 Mg2 (C6 H6 ), which formally contains the anti-aromatic anion C6 H6 2- , reacted with tBuOH as a Brønsted base to 1,3- and 1,4-cyclohexadiene and with H2 as a two electron donor to (DIPeP BDI)2 Mg2 H2 and C6 H6 . It also reductively cleaved the C-F bond in fluorobenzene and gave (DIPeP BDI)MgPh, (DIPeP BDI)MgF, and C6 H6 .

Azide–Alkyne Cycloaddition (CuAAC) in Alkane Solvents Catalyzed by Fluorinated NHC Copper(I) Complex

A highly efficient and environmentally benign protocol for copper‐catalyzed alkyne–azide cycloaddition (CuAAC) in industrially important alkane solvents was developed. New copper(I) complexes bearing NHC ligands decorated with bulky hexafluoroisopropylalkoxy group [(CF3)2(OR)C‐] were first introduced for the process. The complex with isopentyl group [(CF3)2(OiAm)C‐] exhibited the best catalytic activity in the reactions of diversely substituted alkyne and azide substrates in alkane solvents, such as hexane, heptane and cyclohexane. The new CuAAC protocol is easily scalable, synthetically robust, and reproducible; it utilizes low catalyst loadings and enables simple isolation of pure products free from any contaminants including residue of the catalyst and starting materials.

Alkyl-Dimethylpyrazines in Mandibular Gland Secretions of Four Odontomachus Ant Species (Formicidae: Ponerinae).

Ponerine ants are known to contain mixtures of pyrazines in their mandibular glands. We analyzed the mandibular gland contents of four ponerine species (Odontomachus chelifer, O. erythrocephalus, O. ruginodis, and O. bauri) by gas chromatography coupled with mass spectrometry, and found that each species contains specific mixtures of trisubstituted alkylpyrazines among other volatiles. Attempts to identify alkylpyrazines solely by mass spectral interpretation is unrealistic because spectra of positional isomers are indistinguishable. To avoid misidentifications, we synthesized a large number of reference compounds and compared their mass spectral and gas chromatographic properties with those present in the Odontomachus species under investigation. Most of the compounds identified were 2-alkyl-3,5-dimethylpyrazines. Interestingly, when the third substituent was an isopentyl group, the two methyl groups were found to be located at the 2 and 5 ring positions. Using our data, we recognized several misidentifications in previous publications.

Isolation and structural characterization of a novel sibutramine analogue, chlorosipentramine, in a slimming dietary supplement, by using HPLC-PDA, LC–Q-TOF/MS, FT-IR, and NMR

A novel sibutramine analogue was detected in a slimming formula by high performance liquid chromatography with a photo diode detector array (HPLC-PDA). The unknown compound exhibited an ultraviolet (UV) spectrum that was similar to that of chlorosibutramine, despite having a different HPLC retention time. Further analysis of the slimming formula by LC–quadrupole time-of-flight mass spectrometry (LC–Q-TOF/MS) showed that the unknown compound had the formula C18H27Cl2N. To elucidate the structure of this new sibutramine analogue, the target compound in the slimming formula was isolated on a preparative-LC system equipped with a PDA. After analysis by fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy, the unknown compound was identified as a sibutramine analogue in which the iso-butyl group on the side chain is replaced with an iso-pentyl group. This new sibutramine analogue was identified to be 1-(1-(3,4-dichlorophenyl)cyclobutyl)-N,N,4-trimethylpentan-1-amine and has been named as chlorosipentramine.

Bulky Yet Flexible Pd-PEPPSI-IPentAn for the Synthesis of Sterically Hindered Biaryls in Air

In this report, a type of moisture and air stable Pd-PEPPSI-IPentAn complex (C1) with the combination of acenaphthyl on the backbone and isopentyl groups on N-aryl moieties was described and applied in the Suzuki-Miyaura cross-coupling reaction in air. The reaction conditions were optimized, and the structure-reactivity relationships between C1 and other classical efficient Pd-PEPPSI complexes were investigated intensively. Our study demonstrated that both the backbone and N-aryl moieties gave rise to a significant effect on this transformation when exposed to air. A wide range of sterically hindered (hetero)aryl chlorides with (hetero)arylboronic acids were compatible, giving good to excellent isolated yields of sterically hindered bi(hetero)aryls.

Tetrahydrofuran hydrate crystal growth inhibition by bis-and tris-amine oxides

Amine oxides are an alternative, non-ionic class of gas hydrate anti-agglomerant (AA) surfactants that are potentially more environmentally-friendly than cationic surfactant AAs. These classes of AAs work by interacting with hydrate crystal surfaces. Recently, we reported on the clathrate hydrate crystal growth inhibition of monoamine oxides using Structure II (SII) tetrahydrofuran (THF) hydrate (Kelland et al., 2012). It was determined that the best hydrate crystal growth inhibition was provided by amine oxides with n-butyl, n-pentyl or iso-pentyl groups, with tributylamine oxide being the best homofunctional trialkylamine oxide investigated. However, replacement of one butyl group with a larger group, forming the tail of an AA surfactant, lowered the inhibition significantly which could have consequences for the use of mono-amine oxides as AAs.We have now investigated bis-amine oxides and discovered that they can give even greater THF hydrate crystal growth inhibition than mono-amine oxides, particularly when the amine oxides have the correct size alkyl groups and are an optimum distance apart. The optimum alkyl group was found to be n-butyl and the optimum distance for bis-amine oxides is with a chain of 5–6 sp3 carbon atoms separating the nitrogen atoms. Alternatively, a heteroatom can be placed in this spacer chain, for example a third nitrogen atom, such as for alkylated derivatives of diethylenetriamine. These results mean that the use of bis-amine oxide surfactants could potentially lead to improved AA performance compared to mono-amine surfactants because of their greater adsorption onto hydrate surfaces. They may also act as improved synergists for polymeric kinetic inhibitors of natural gas hydrates.

Isoprenyl-thiourea and urea derivatives as new farnesyl diphosphate analogues: Synthesis and in vitro antimicrobial and cytotoxic activities

A series of new isoprenyl-thiourea and urea derivatives were synthesized by the reaction of alkyl or aryl isothiocyanate or isocyanate and primary amines. The structures of the compounds were established by 1H NMR, 13C NMR, MS, HRMS and elemental analysis. The new compounds were screened for in vitro antimicrobial activity against seven strains representing different types of gram-positive and gram-negative bacteria. More than a third of the synthesized compounds showed variable inhibition activities against the tested strains. Best antimicrobial activities were found for those thiourea analogues with 3-methyl-2-butenyl, isobutyl or isopentyl groups and aromatic rings possessing electron withdrawing substituents. The new compounds were also subjected to a preliminary screening for antitumoral activity. The presence of a highly lipophilic group and an electron withdrawing group in the aromatic rings enhanced anticancer activity of the synthesized compounds, showing in most cases more activity than that of the controls.

Synthesis and biological activity of both enantiomers of kujigamberol isolated from 85-million-years-old Kuji amber

The full-structure of a norlabdane terpenoid, kujigamberol (1) was determined by total synthesis. Key features of the total synthesis are (1) installation of isopentyl group through an o-lithiation of benzamide, (2) construction of tetralone by the RCM reaction, and (3) optical resolution of (±)-1 using chromatographical separation of the corresponding camphanates. X-ray crystallographical analysis of p-bromobenzoate obtained from the more polar camphanate that was identical with a natural derivative, revealed natural kujigamberol to have an S-configuration. Both the natural enantiomer and its (R)-antipode showed the same inhibitory activity toward the mutant yeast and HL-60 cells, while simple analogs without alkyl groups at the C-8 and 9 positions of (±)-1 had no such activity

Tetra(iso-hexyl)ammonium Bromide—The Most Powerful Quaternary Ammonium-Based Tetrahydrofuran Crystal Growth Inhibitor and Synergist with Polyvinylcaprolactam Kinetic Gas Hydrate Inhibitor

Tetraalkylammonium salts, particularly with several n-butyl or n-pentyl or iso-pentyl groups, have previously been shown to be excellent structure II (SII) gas and tetrahydrofuran (THF) hydrate crystal growth inhibitors. We have investigated the ability of quaternary ammonium salts with isoalkyl groups with 5 to 7 carbons atoms to inhibit the growth of tetrahydrofuran (THF) hydrate crystal. Two new quaternary salts were synthesized for the first time: tetra(iso-hexyl)ammonium bromide (TiHexAB) and tetra(iso-heptyl)ammonium bromide (TiHepAB). It was found that tetra(iso-pentyl)ammonium bromide (TiPeNB) gave poorer crystal growth inhibition than isomeric tetra(n-pentyl)ammonium bromide (TPAB) but similar performance to tetra(n-butyl)ammonium bromide (TBAB). However, TiHexAB gave better inhibition than any quaternary ammonium previously reported, including TPAB. TiHepAB was a poorer THF hydrate crystal growth inhibitor, similar in performance to isomeric tetra(n-hexyl)ammonium bromide. We believe the reason ...

Synthesis, lead lability and ring deformation of three 1,4,8,11,15,18,22,25-octasubstituted phthalocyaninato lead derivatives

The syntheses and attempted syntheses of some non-peripherally (1,4,8,11,15,18,22,25) octasubstituted lead phthalocyanines from their corresponding metal-free derivatives are described. Some compounds exhibited lability of the lead ion during work-up to regenerate the starting material. The results of single crystal X-ray diffraction analyses of 1,4,8,11,15,18,22,25-octahexyl-, 1,4,8,11,15,18,22,25-octa-iso-pentyl- and 1,4,8,11,15,18,22,25-octahexylsulfanyl lead phthalocyanines are reported and cast some light on the greater stability of 1,4,8,11,15,18,22,25-octahexylsulfanyl lead phthalocyanine, in terms of ease of loss of the lead ion, over the other two substituted lead phthalocyanines studied. The phthalocyanine cores of all three derivatives adopt a saddle-shaped geometry rather than the saucer-shaped conformation exhibited by unsubstituted lead phthalocyanine. The saddle-shaped conformation would appear to offer a means of relieving steric interactions between the substituents on adjacent benzene rings. That steric interactions are a feature of these molecules is perhaps reflected in the different distortions of the saddle conformations. This is greatest for compound 1,4,8,11,15,18,22,25-octa-iso-pentyl lead phthalocyanine bearing the isopentyl groups, expected to introduce the most interactions, and least for compound 1,4,8,11,15,18,22,25-octahexylsulfanyl lead phthalocyanine where S atoms rather than methylene groups are adjacent to the benzene ring. The molecules of 1,4,8,11,15,18,22,25-octahexyl- and 1,4,8,11,15,18,22,25-octahexylsulfanyl lead phthalocyanine pack together in pairs with their nearest neighbouring molecule; their lead atoms, displaced from the core and directed towards each other. The presence of the S atoms in 1,4,8,11,15,18,22,25-octahexylsulfanyl lead phthalocyanine leads to close Pb … S contacts between the molecules. Attractive Pb … S interactions in this compound may also account for the larger displacement of the Pb from the mean-plane of the four coordinated nitrogen atoms at the centre of the phthalocyanine core than is found for 1,4,8,11,15,18,22,25-octahexyl- and 1,4,8,11,15,18,22,25-octa-iso-pentyl lead phthalocyanines. The molecular packing of 1,4,8,11,15,18,22,25-octa-iso-pentyl lead phthalocyanine is more complex because of the presence of tetrahydrofuran molecules (the solvent of recrystallisation) within the crystal, offering additional interactions with the Pb atoms.

Isopentyltriphenylphosphonium bromide methanol solvate

At 102 K, the isopentyl group of the title compound, C23H26P+·Br−, is in the extended conformation. The phenyl rings are in the propeller configuration usually found in this family of triphenylphosphonium compounds. The methanol solvent molecule is hydrogen bonded to the bromide ion.

The Solvent Extraction of Boron with Synthesized Aliphatic 1,3‐Diols: Stripping and Extraction Behavior of Boron by 2,2,5‐Trimethyl‐1,3‐hexanediol

A variety of aliphatic 1,3‐diols (4a–c, 5a–c, 6a–c) was synthesized from β‐hydroxy carbonyl compounds (1–3) for potential use in the solvent extraction of boron. Primary‐secondary and primary‐tertiary alcohol structures of 1,3‐diols substituted with isopropyl, isobutyl, and isopentyl groups have been demonstrated to be very efficient for the solvent extraction of boric acid from aqueous solutions. The extraction ability of 2,2,5‐trimethyl‐1,3‐hexanediol (5b) was investigated as a function of 5b concentration, solution pH, solvent properties, and stripping conditions. Extraction efficiency increased with increasing concentration of 5b, and the best extraction of boron (96.8%) was found to be at an equilibrium pH of 2 with 0.5 M of 5b. Chloroform, toluene, chlorobenzene, 2‐octanol, and n‐amyl alcohol were found to be suitable solvents for the solvent extraction of boron. The boron complex can be recovered from the organic phase by treatment with an aqueous solution of sodium hydroxide. The highest ratio (96.7%) of boron was recovered by 0.1 M of sodium hydroxide solution.

Effects of certain resorcinol derivatives on the tyrosinase activity and the growth of melanoma cells.

Effects of certain resorcinol derivatives on tyrosinase activity, melanin formation and some other biological activities were studied in order to develop a new, potent depigmentor and/or antimelanoma drug. NKO-09, having isopentyl group in position 6 of resorcinal, exhibited a more potent effect than the compounds which have methyl (NKO-10), ethyl (NKO-11), hexyl (KOM-14), octyl (NKO-14), decyl (NKO-19), dodecyl (NKO-15) and tetradecyl (NKO-16) group in inhibiting the tyrosinase activities (both tyrosine hydroxylation and dopa oxidation). NKO-09 was more potent than hydroquinone in inhibiting the tyrosine hydroxylation; furthermore, NKO-09 inhibited the dopa oxidation different from hydroquinone. In the studies on melanin formation, protein synthesis and the growth of the melanoma cells, NKO-09 caused the most potent effect among the test compounds, except for the growth of the melanoma cells. KOM-14 was more potent than NKO-09 in the antimelanoma activity, and its effect was superior than that of 5-fluorouracil. From these findings, it is suggested that NKO-09 and KOM-14 can be used as an efficacious depigmentor and antimelanoma drug, respectively.

An unexpected γ‐hydrogen rearrangement in the mass spectra of di‐ortho ‐substituted alkylbenzenes

AbstractIn contradiction of long‐accepted mass spectrometric dogma, the site‐specific γ‐hydrogen rearrangement is observed in alkylbenzenes in which both ortho positions are blocked with methyl substituents. Mass spectrometric studies of a series of five trimethyl‐ and three tetramethylisopentylbenzenes have shown that this rearrangement is only suppressed to a significant degree in those compounds in which all three positions ortho and para to the isopentyl group are blocked. Deuterium labelling has confirmed the γ‐site‐specific origin of the migrating H atom while metastable studies have been used to investigate the mechanism of the rearrangement process.