Reactivity of chlorodeoxypseudoephedrines with oxo-, thio-, and selenocyanates

Herein, the reactivity of chlorodeoxypseudoephedrine hydrochlorides with oxo-, thio-, and selenocyanate nucleophiles is reported. 1,3-Heterazolidine-2-iminium or ammonium salts were obtained stereoselectively in most cases. The hard–soft nature of the calcogen atom determines the mechanistic pathway via an S_N2 (X = O), aziridine intermediate (X = Se), or both (X = S). A simple method to synthesize stereoselectively the trans-isomer of 3,4-dimethyl-5-phenyl-oxazolidine-2-iminium chloride and the cis-isomer of 4-methyl-5-phenyl-oxazoline-2-ammonium chloride, was also found. In addition, heterazolidine-2-imines or amines were liberated from the corresponding salts [Cl⁻ or XCN⁻ (X = O, S, Se)] with aqueous NaOH. Finally, cis-3,4-dimethyl-5-phenyl-oxazolidine-2-iminium chloride, cis-4-methyl-5-phenyl-oxazoline-2-amine, and trans-4-methyl-5-phenyl-selenazoline-2-amine compounds were studied by X-ray diffraction.     

(Vapour + liquid) equilibria for the binary mixtures (cis-pinane + α-pinene) and (cis-pinane + 1-butanol)

The isothermal and isobaric (vapour + liquid) equilibria for (cis-pinane + α-pinene) and (cis-pinane + 1-butanol) measured with an inclined ebulliometer are presented. The experimental results are analysed using the UNIQUAC equation with the temperature-dependence binary parameters with satisfactory results. Experimental vapour pressures of cis-pinane are also included.     

The infrared spectrum of bis(fluorosulfonyl)imide revisited: Attractive performances of the PBE0/6-31G** model

We report a systematic investigation of the far- and mid-infrared spectra of ionic liquids (ILs) containing the bis(fluorosulfonyl)imide (FSI) anion, both in the liquid state at room temperature and in solid phases at low temperatures. We extended to lower frequencies a previous study, and we observed four additional vibration bands below 500 cm⁻¹, attributable to FSI. Moreover, DFT calculations of vibration frequencies were performed using three combinations of theory and basis set: (1) B3LYP/6-31G**, (2) B3LYP/6-311 + G(3df) and (3) PBE0/6-31G**. Model 1, largely used in the previous literature concerning ILs, shows the poorest performances; model 2, which generally gives a good agreement with the experiments, misses the vibration frequencies by ∼40 cm⁻¹ in the range 650–900 cm⁻¹ where one finds the largest spectral differences between cis- and trans-FSI; model 3 gives the best agreement with the experiments and, moreover, is much less time consuming than model 2. The comparison with calculations suggests that the band centered around 1217 cm⁻¹ is a good marker of the occurrence of the cis-FSI conformer. Finally, the bands located around 730 and 750 cm⁻¹ are attributable to cis- and trans- conformer of FSI, respectively.     

A DFT study on group III and V combined hexagonal clusters as potential building motifs for inorganic nanomaterials

A detail theoretical investigation on the structure and electronic properties of inorganic hexagonal units and their higher order derivatives comprising group III (B, Al and Ga) and V (N, P and As) elements is performed. A series of 45 clusters, formed by a linear combination of hydrogen saturated hexagonal motifs up to five units, (MY)_2n+1H_2n+4 (M = B, Al, Ga; Y = N, P, As; n = 1–5) are considered to look into their metal–insulator–semiconductor (MIS) behavior. It is evident from the present study that the arsenic doped group III hexagonal units clearly have a decisive role in forming semiconductor materials.     

Kβ/Kα X-ray intensity ratios for elements in the range 16⩽Z⩽92 excited by 5.9, 59.5 and 123.6 keV photons

The K shell intensity ratios K_β/K_α for 59 elements in the atomic region 16⩽Z⩽92 have been measured at excitation energies of 5.9, 59.5 and 123.6 keV. K X-rays emitted by samples have been counted by a Si(Li) detector with resolution 160 eV at 5.9 keV. The measured values were compared with the theoretical values calculated using Scofield's tables based on the Hartree–Slater and Hartree–Fock theories and available experimental values. Reasonable agreement is typically obtained between present and theoretical values.     

Diterpenoids from the aerial parts of Leonurus macranthus

One cis clerodane-type (1) and three highly oxygenated labdane-type diterpenes (2-4) were isolated from the aerial parts of Leonurus macranthus. Compound 1 represents the first example of cis clerodane-type diterpene in the plants of Leonurus genus.     

Spin-crossover in dimeric hydrogen-bonded iron(II) 2-(pyrazolyl)-pyridine and 2-(imidazolyl)-pyridine complexes

Five new hydrogen-bonded solvated iron(II) complexes of pyrazolyl- and imidazolyl-based N,N-chelating ligands have been synthesised. Water to ligand-NH hydrogen-bonded bridges occur in the pseudo-dimeric complexes {cis-[Fe(pypzH)₂(NCX)₂]₂(μ-OH₂)(H₂O)₂} · H₂O · MeOH (where X = S or Se), and in the chain complex {cis-[Fe(pypzH)₂(NCS)₂](μ-OH₂)}_n. A “half” spin-crossover (T_c = 125 K) was observed in the dimeric X = Se complex by means of magnetic measurements and no thermal hysteresis occurred between 4 and 300 K. The crystal structure at 123 K showed Fe–N distances consistent with the magnetism. Each Fe in the dimeric unit was structurally equivalent in the HS–LS state. Removal of the solvate molecules led to HS–HS behaviour over the temperature range 4–300 K. The pseudo-dimer with X = S also showed HS–HS behaviour as did the monomeric analogue cis-[Fe(pypzH)₂(NCS)₂]H₂O and a structurally different methanol-bridged dimer {cis-[Fe(pyimH)₂(NCS)₂]₂(μ-MeOH)₂} · 2MeOH (pypzH = 2-(1H-pyrazol-3-yl)-pyridine; pyimH = 2-(1H-imidazol-2-yl)-pyridine).     

Spectra and structure of silicon containing compounds: XXIX. Conformational studies of methyl vinyl difluorosilane from temperature dependent FT-IR spectra of xenon and krypton solutions

Variable temperature (−55 to −150°C) studies of the infrared spectra (3500–400 cm⁻¹) of methyl vinyl difluorosilane, CH₂CHSiF₂CH₃, dissolved in liquid xenon and krypton have been recorded. Utilizing three sets of conformer doublets due to the cis and gauche rotamers from the krypton solution and two pairs from the xenon solution, the enthalpy difference has been determined to be 67±7 cm⁻¹ (0.80±0.09 kJ/mol) and 83±11 cm⁻¹ (0.99±0.14 kJ/mol), respectively, with the gauche conformer the more stable form. However, in the crystalline solid only the cis conformer is present. Ab initio calculations have been carried out with several different basis sets up to MP2/6-311+G(2d,2p) with full electron correlation by the perturbation method from which the conformational stabilities have been determined. With the largest basis set MP2/6-311+G(2d,2p), the cis conformer is predicted to be the more stable conformer by 10 cm⁻¹ which is inconsistent with the experimental results; however, this value is so small that the ab initio prediction cannot be relied on to give the correct conformer stability. The spectroscopic and theoretical results are compared to the corresponding quantities for some similar molecules.     

Enantioselective acylation of rac-2-phenylcycloalkanamines catalyzed by lipases

The kinetic resolution of some 2-phenylcycloalkanamines was performed by means of aminolysis reactions catalyzed by lipases, with Kazlauskas’ rule being obeyed in all cases. The size of the ring and the stereochemistry of the stereogenic centers of the amines had a strong influence on both the enantiomeric ratio and the reaction rate of these aminolysis processes. Lipase B from Candida antarctica (CAL-B) showed excellent enantioselectivities toward trans-2-phenylcyclohexanamine in a variety of reaction conditions (E >150), whereas lipase A from C. antarctica (CAL-A) was the best catalyst for the acylation of cis-2-phenylcyclohexanamine (E = 34) and trans-2-phenylcyclopropanamine (E = 9).     

Robust polyazobenzene microcapsules with photoresponsive pore channels and tunable release profiles

Monodisperse silica particles coated with azobenzene polymer (PAzo) shell were synthesized through distillation precipitation polymerization. Robust PAzo microcapsules were obtained after selective removal of the silica templates by hydrofluoric acid (HF) etching. These PAzo microcapsules, confirmed by transmission electron microscopy (TEM) investigation, had excellent reversible photoisomerization with transformation between trans and cis isomers under ultraviolet (UV) and visible lights. Due to their compatibility with PAzo, acetonitrile would be trapped in the network of the shell during polymerization. Pore channels in the shell, confirmed by nitrogen adsorption–desorption test, would be produced after acetonitrile evaporation. Loading and release of rhodamine B (RhB) molecules in PAzo microcapsules were carried out and indicated that cis azobenzene showed larger pore diameter (named as “open switch”) under UV light which favored permeation of RhB molecules, while trans structure (named as “closed switch”) under visible light slowed down the process. In addition, both release profiles obeyed pure Fickian diffusion with a power law of t^0.42. Diffusion coefficient of RhB from PAzo microcapsules under visible light (1.47 × 10^?12 cm²/s) was lower than that under UV light (2.12 × 10^?12 cm²/s).     

Do lipases also catalyse the ring cleavage of inactivated cyclic trans-β-lactams?

Twelve-membered cyclic cis- and trans-β-lactams 1b and 2b and the corresponding cyclic cis- and trans-β-amino acid enantiomers, 1a, 1c and 2a, 2c were prepared through the CAL-B-catalysed enantioselective ring cleavage of racemic cis-13-azabicyclo[10.2.0]tetradecan-14-one, (±)-1, and trans-13-azabicyclo[10.2.0]tetradecan-14-one, (±)-2. High enantioselectivities (E >200) were observed for the ring opening of both the cis- and trans-β-lactams when the Lipolase-catalysed reactions were performed with 0.5 equiv of H₂O in i-Pr₂O at 70 °C. The resolved β-lactams 1b and 2b (yield ⩾47%) and β-amino acids 1a and 2a (yield ⩾32%) could be easily separated.     

Density functional theory study of ring-chain equilibria for the cross-metathesis of cyclohexene and cis,cis-cycloocta-1,5-diene with functionalized olefins

The computational modeling of ring-chain equilibria for the ring-opening cross-metathesis of cyclohexene (CH) with 1,2-dicarbomethoxy-ethylene (DCE), 1,4-dicarbomethoxy-but-2-ene (DCB) and ethylene at T = 298.15 K using the B3LYP/6-31G(d,p) level of theory revealed that CH and ring-opened products equilibrium is shifted towards the thermodynamically stable six-membered ring. The calculations demonstrated that carbonyl-containing olefins can completely drive the equilibrium in the cross-metathesis with cis,cis-cycloocta-1,5-diene (COD) towards the ring-opened products.     

Gamma irradiation effect on the enzymatic activities of horseradish and apple peroxidases

The behavior at low-dose exposure (0.033–0.4 kGy) of horseradish peroxidase (HRP) and of two different purified fractions of apple (Jonathan cultivar) peroxidases (named APR_1S and APR_2S) was studied. The HRP solutions were added with either 0.32 M fructose or glucose in order to study their effect on enzymes activity response under γ (¹³⁷Cs, dose rate 0.4 kGy/h) irradiation. The obtained results showed similar behavior between HRP-sugar-added solution and apple fraction with higher oligosaccharides content (APR_2S) undergoing low-dose treatment. The same pattern was observed between unglycosylated HRP and APR_1S with lower oligosaccharides content. These similarities gave us the possibility to conclude that the presence of oligosaccharides, in more or less quantities, influences in the same way the peroxidases activity, from different plant species, exposed to γ irradiation.     

Cyclohexadecanone derivative/γ-cyclodextrin complexes MD simulations and AMSOL calculations in vacuo and in aquo compared with experimental findings

The complex formations of cis- and trans-cyclohexadecenone (cis-CHDC and trans-CHDC) and cyclohexadecanone (CHDH) with γ-cyclodextrin (γ-CD) in the presence of water are investigated. In the experiment [cis-CHDC//γ-CD] complexes are found to be slightly preferred over [trans-CHDC//γ-CD] complexes, with an energy difference of less than 1 kcal/mol. Molecular dynamics (MD) simulations in vacuo showed that energetically favourable complexes are formed, whereby (contrary to experiment) trans-CHDC has the best complexation energy, followed by cis-CHDC, (their calculated energy difference being less than 3 kcal/mol) and then cyclohexadecanone (CHDH). MD simulations in aqueous solution reveal positive complexation energies for all three compounds of about 12 to 25 kcal/mol, i.e., these practically do not exist in aquo, which is in agreement with the experimental observation that about 99% precipitate is formed. AMSOL calculations of the hydration energies support the low solubility of all three CHDC derivatives and the high solubility of γ-CD. Therefore, the simulations in aquo showed that hydration can play such an important role, that although complexation is possible in vacuo, the complexes are not formed in water.     

Gap-mode SERS studies of azobenzene-containing self-assembled monolayers on Au(1 1 1)

Self-assembled monolayers of azobenzene-containing thiols on smooth Au(1 1 1) surfaces were studied by gap-mode surface-enhanced Raman spectroscopy (gap-mode SERS). By adsorption of colloidal Au nanoparticles on top of the organic adlayer highly reproducible spectra with strongly enhanced intensities are obtained. The observed bands indicate a trans conformation of the azobenzene moieties and are in agreement with structural data for the molecular layer. A characteristic dependency on the terminal and the spacer groups of the molecules is found. Samples prepared during illumination with UV light show pronounced spectral differences that can be attributed to azobenzene in cis conformation.     

Genomic studies on nitrogen metabolism in Halomonas boliviensis: Metabolic pathway,biochemistry and evolution

Halomonas boliviensis LC1^T = DSM 15516^T is a halophilic bacterium that copiously produces osmolytes and polyesters. The growth of H. boliviensis is restricted when glutamate or glutamine is not included in its culture medium. The concentration of glutamate in the medium can regulate the production of either osmolytes or polyesters. However, genomic studies on the nitrogen assimilation have not been performed on H. boliviensis and other members of the family Halomonadaceae. Glutamate metabolism in H. boliviensis was discerned based on genome sequence analysis. The genome sequences of other Halomonadaceae members revealed similar enzymes to those found in H. boliviensis. H. boliviensis and H. elongata DSM 2581^T acquired distinct glutamate dehydrogenase genes through horizontal gene transfer from a different bacterium. Two alleles of glutamine synthetase could be found in H. boliviensis, one of which was obtained from a thermophilic archaeon via horizontal gene transfer. Two subunits of glutamate synthase were also present in H. boliviensis. The small β-subunit had a molecular weight of 52 kDa and was phylogenetically closely affiliated to proteins of other halomonads and Gammaproteobacteria. The large (161 kDa) α-subunit of the halomonads gathered in a separate phylogenetic group, hence glutamate synthase α-subunits of halomonads may be included a novel group of enzymes. Furthermore, putative enzymes obtained from the genome of H. boliviensis should permit complete glutamate metabolism. A similar metabolism should be followed by other halomonads. However, some phenotypic differences between halomonads, such as the ability to assimilate ammonia, resulted as a consequence of horizontal gene transfer. Each enzyme that forms part of the glutamate metabolism in prokaryotes evolved following a different pattern. Yet, most enzymes of halomonads diverged in phylogenetic clusters composed of Proteobacteria, as might be expected.     

Thermal reactivity of cis- and trans-bis(triphenylgermyl)bis(tertiary phosphine)platinum(II)

The complex cis-Pt(Ph₃Ge)₂(PMe₂Ph)₂ underwent smooth isomerization to give the trans-isomer at room temperature via an associative five-coordinated intermediate. Thermodynamic parameters and activation energy for the cis to trans isomerization were obtained, ΔH^# = 105 kJ mol⁻¹, ΔS^# = 12.5 J mol⁻¹ K⁻¹, and Ea = 107 kJ mol⁻¹, respectively. Heating of trans-Pt(Ph₃Ge)₂(PMe₂Ph)₂ at 50 °C for 36 days produced trans-PtPh(Ph₃Ge)(PMe₂Ph)₂ followed by the formation of trans-PtPh₂(PMe₂Ph)₂, Pt(PMe₂Ph)₄, and Ph₄Ge finally via elimination of the phenyl group from Ph₃Ge ligand with liberation of the Ph₂Ge unit and subsequent reductive elimination of the remaining Ph₃Ge ligand at 80 °C for 1 month.     

A ruthenium(II) complex with the propionate ion: Synthesis,characterization and cytotoxic activity

The complex [Ru(η²-O₂CCH₂CH₃)(dppe)₂]PF₆ (dppe = 1,2-bis(diphenylphosphino)ethane) was prepared and characterized by elemental analysis, spectroscopic techniques, X-ray crystallography, HRESIMS and HRESIMS/MS. The characterization data are consistent with a cis arrangement for the dppe ligands and a bidentate coordination of the propionate ligand through carboxylate oxygens. Cytotoxicity assays were carried out on human and murine cancer and normal cell lines. In general, the [Ru(η²-O₂CCH₂CH₃)(dppe)₂]PF₆ complex was more cytotoxic than both its precursor cis–[RuCl₂(dppe)₂] and the reference metallodrug cisplatin. The best results against the HepG2 human tumour cell line and S180 murine tumour cell line were found with IC₅₀ values of 6.5 ± 0.2 and 0.18 ± 0.03 μM, respectively.