C1 C12 Research Articles

Effect of Organic Counterions on the Properties of N-Lauryl Diisopropanolamine Surfactants

The influence of counterions on the surface properties of N-lauryl diisopropanolamine surfactants is delineated using conductometry and surface tension measurements. Twelve types of organic counterions have been studied: C1–C12 monocarboxylic acids anions. The surface properties of the synthesized surfactants, including surface tension, critical micelle concentration (CMC), effectiveness (πCMC), efficiency (pC20), maximum surface excess (Γmax), minimum surface area (Amin), Gibbs energy of micellization (ΔGmic), and adsorption (ΔGad) processes in the aqueous. The biodegradability of the prepared surfactants was tested in river water using the die-away method. Petroleum-collecting and petroleum-dispersing capacities of the synthesized compounds on the surface of water of varying mineralization degree have been studied.

Thermal Behavior of Potassium C1–C12 n-Alkanoates and Its Relevance to Fischer–Tropsch

The thermal behavior of potassium C1–C12 n-alkanoates (K-carboxylates) were studied over the temperature range T/K = (243 to 873). A number of problems in industrial Fischer–Tropsch facilities were attributed to these compounds, but this study also revealed some beneficial effect that may directly be related to the thermal behavior of potassium methanoate. The unusually low melting point of potassium methanoate, T/K = (442.2 ± 0.3), combined with its thermal stability to T/K ≈ (693), may explain the ease of distribution of the potassium promoter of iron-based Fischer–Tropsch catalysts during synthesis even when potassium promoter is added separately. The C2–C12 K-carboxylates were all thermally stable at temperatures T/K ≤ (713), and significant mass loss was not observed at T/K ≤ (748). The thermal stability and high melting point of potassium propanoate, T/K = (636.9 ± 0.3) and potassium butanoate, T/K = (623.1 ± 0.3), in particular caused these compounds to be prone to cause pressure drop problems in r...

Comparison of outcomes after atlantoaxial fusion with transarticular screws and screw-rod constructs.

ObjectiveThe purpose of this study was to compare the radiological and neurological outcomes between two atlantoaxial fusion method for atlantoaxial stabilization; C1 lateral mass-C2 pedicle screws (screw-rod constructs, SRC) versus C1-2 transarticular screws (TAS).MethodsForty-one patients in whom atlantoaxial instability was treated with atlantoaxial fixation by SRC group (27 patients, from March 2005 to May 2011) or TAS group (14 patients, from May 2000 to December 2005) were retrospectively reviewed. Numeric rating scale (NRS) for pain assessment, Oswestry disability index (ODI), and Frankel grade were also checked for neurological outcome. In radiologic outcome assessment, proper screw position and fusion rate were checked. Perioperative parameters such as blood loss during operation, operation time, and radiation exposure time were also reviewed.ResultsThe improvement of NRS and ODI were not different between both groups significantly. Good to excellent response in Frankel grade is shown similarly in both groups. Proper screw position and fusion rate were also observed similarly between two groups. Total bleeding amount during operation is lesser in SRC group than TAS group, but not significantly (p=0.06). Operation time and X-ray exposure time were shorter in SRC group than in TAS group (all p<0.001).ConclusionBoth TAS and SRC could be selected as safe and effective treatment options for C1-2 instability. But the perioperative result, which is technical demanding and X-ray exposure might be expected better in SRC group compared to TAS group.

Transesterification of a series of 12 parabens by liver and small-intestinal microsomes of rats and humans

Hydrolytic transformation of parabens (4-hydroxybenzoic acid esters; used as antibacterial agents) to 4-hydroxybenzoic acid and alcohols by tissue microsomes is well-known both in vitro and in vivo. Here, we investigated transesterification reactions of parabens catalyzed by rat and human microsomes, using a series of 12 parabens with C1–C12 alcohol side chains. Transesterification of parabens by rat liver and small-intestinal microsomes occurred in the presence of alcohols in the microsomal incubation mixture. Among the 12 parabens, propylparaben was most effectively transesterified by rat liver microsomes with methanol or ethanol, followed by butylparaben. Relatively low activity was observed with longer-side-chain parabens. In contrast, small-intestinal microsomes exhibited higher activity towards moderately long side-chain parabens, and showed the highest activity toward octylparaben. When parabens were incubated with liver or small-intestinal microsomes in the presence of C1–C12 alcohols, ethanol and decanol were most effectively transferred to parabens by rat liver microsomes and small-intestinal microsomes, respectively. Human liver and small-intestinal microsomes also exhibited significant transesterification activities with different substrate specificities, like rat microsomes. Carboxylesterase isoforms, CES1b and CES1c, and CES2, exhibited significant transesterification activity toward parabens, and showed similar substrate specificity to human liver and small-intestinal microsomes, respectively.

Lithium C1–C12n-Alkanoates: Thermal Behavior from −30 °C to 600 °C

The lithium C1–C12n-alkanoates (Li-carboxylates) were synthesized, and their thermal behavior was studied over the temperature range t/°C = (−30 to 600). Infrared and Raman spectroscopy indicated that the C3–C12 Li-carboxylates exist in two different configurations and that these configurations persisted after melting. In both configurations the equivalence of the C–O bonds were retained. Evidence for covalent character of the Li–O bond was found only for lithium methanoate. Solid–solid phase transitions were observed for all C1–C12 Li-carboxylates, with the exception of lithium butanoate, hexanoate, and octanoate. No liquid crystal phases were found for any of the C1–C12 Li-carboxylates. These observations were consistent with literature. A previously unreported solid–solid transition at temperature t/°C = (41.3 ± 0.3) with enthalpy ΔH/kJ·kg–1 = (2.8 ± 0.1) was observed for lithium dodecanoate. The melting points of the C1–C2 Li-carboxylates were t/°C = (272 and 283) respectively. For the other Li-carboxylates, the melting points decreased monotonically from t/°C = (331) for lithium propanoate, to t/°C = (227) for lithium dodecanoate. The experimental values for melting point temperature and enthalpy of melting were consistent with literature. Thermal decomposition produced lithium carbonate (Li2CO3) as solid residue and took place at t/°C = (380 to 390) for C1–C2 Li-carboxylates and t/°C = (450 to 485) for C3–C12 Li-carboxylates.

Routine sectioning of the C2 nerve root and ganglion for C1 lateral mass screw placement in children: surgical and functional outcomes

Adult studies have shown that sectioning the C2 nerve root and ganglion may facilitate placement of C1 lateral mass screws and lead to decreased operative time and blood loss. We report the functional outcomes and complications following routine sectioning of the C2 nerve root and ganglion, which have not been reported in pediatric patients. Fifteen consecutive pediatric patients underwent C1 lateral mass screw insertion and bilateral C2 nerve root and ganglion sectioning. Clinical and radiographic assessments were performed at follow-up. Numbness in the C2 distribution and/or occipital neuralgia, operative times, estimated blood loss (EBL), length of stay (LOS), and complications were recorded. Average follow-up time was 35.7months. Overall mean operative time was 250.5min, LOS was 8.46days, and EBL was 337cc. When considering only atlantoaxial fusions, mean operative time was 180.7min and EBL was 97.1cc. There were no intraoperative complications, and no patient reported new onset occipital neuralgia or numbness in the C2 distribution that would interfere with daily living. Of the patients, 93% achieved Lenke fusion grade A; one achieved Lenke fusion grade B. Routine C2 nerve root sectioning and ganglionectomy enhanced surgical exposure of the C1 lateral mass and C1-2 facet joint, potentially maximizing fusion rate and minimizing intraoperative complications. This technique may yield favorable operative times, EBL, and LOS in children undergoing C1 lateral mass screw insertion without negatively affecting functional outcome.

Toward a modular, bidirectional synthesis of (−)-mucocin

A convergent stereoselective synthesis of the C13–C34 fragment of (−)-mucocin is described. The salient features include (a) the bidirectional synthesis of the C-2 symmetric C13–C21 subunit, (b) regio- and stereoselective preparation of a 1,3-diol derivative from a diene activated by NBS via intramolecular nucleophilic sulfinyl group participation, (c) utilizing the self-metathesis reaction to prepare a functionalized C10 alkene, and (d) regio- and stereoselective intermolecular epoxide opening to construct the ether bond between C20 and C24. An organocatalytic α-hydoxylation has been employed to create the C4 stereogenic center of C1–C12 subunit. Attempted union of the two subunits utilizing the B-alkyl Suzuki coupling did not succeed.

Studies towards the total synthesis of (−)-callystatin A

The synthesis of C1–C12 and C13–C22 fragments of (−)-callystatin A is accomplished employing desymmetrization strategy for the creation of five chiral centres of the polypropionate fragment and application of cross-metathesis (CM) reaction for the first time for this molecule.

Total synthesis of the antiinflammatory and proresolving protectin D1

Stereoselective total synthesis of protectin D1 was completed through construction of the Z, E, E-triene structure by using the Suzuki coupling between the vinyl borane (C13–C22) and the vinyl iodide (C1–C12). The Z-enyne, the acetylene precursor of the vinyl borane was synthesized from optically active γ-TMS allylic alcohol in a straightforward way. On the other hand, the vinyl iodide was prepared by using Wittig reaction between the C8–C12 aldehyde possessing the requisite iodo-olefin moiety and the C1–C7 phosphonium iodide.

2-(7-methyl-1H-benzoimidazol-2-yl)-6-(1-aryliminoethyl)pyridinylnickel complexes: Synthesis, characterization and their ethylene oligomerization

Abstract A series of 2-(methyl-substituted-1H-benzoimidazol-2-yl)-6-(1-aryliminoethyl)pyridines (L1–L6) were synthesized and used as N^N^N tridentate ligands for their nickel complexes (C1–C12). All ligands were fully characterized by elemental, NMR and IR spectroscopic analyses, while their nickel complexes were characterized by elemental and IR spectroscopic analyses. The single-crystal X-ray diffraction reveals that the complexes C1, C3 and C9 have distorted octahedral geometry around the Ni center. All nickel complexes, activated with Et2AlCl, exhibit good catalytic activities toward ethylene oligomerization with major dimerization.

Biomechanical Assessment of Bilateral C1 Laminar Hook and C1-2 Transarticular Screws and Bone Graft for Atlantoaxial Instability

STUDYDESIGN: In vitro biomechanical test was conducted to compare the stability of 5 different atlantoaxial posterior fusion techniques. To evaluate the biomechanical stability of an atlas laminar hook combined with transarticular (TA) screws relative to 4 different conventional fusion techniques. The atlantoaxial instability caused by fractures, rheumatoid arthritis, congenital deformity, or traumatic lesions of the transverse ligament often result in acute or chronic spinal cord compression, a possible threat to a patient's life. Posterior atlantoaxial fixations are used to reconstruct the stability of atlantoaxial articulation. Conventional posterior atlantoaxial fixations are associated with high rates of pseudoarthrosis and carry the potential risk of neurologic complication. TA screw fixation can provide an excellent biomechanical stability. As a modified 3-point fixation technique, the bilateral C1-2 TA screws have been combined with C1 laminar hook and bone grafts. This modified technique had carried good clinical outcomes. Eight human specimens (C0-C4) were loaded nondestructively with pure moments and the range of motion at the level of C1-C2 was measured. Eight specimens were implanted with each of the following techniques, respectively: Gallie fixation, C1-2 TA screw fixation combined with Gallie fixation, C1-2 TA screw fixation, C1 laminar hook combined with C1-2 TA screw fixation plus bone grafts, and the C1 lateral mass screws in the atlas combined with C2 isthmic screws in axis. Although the C1-2 TA screws best restricted lateral bending and axial rotation, the modified 3-point fixation technique additionally restricted flexion-extension and provided the excellent stability. Differences in axial rotation and lateral bending (with + or - 1.5 Nm load) were observed when the 3-point fixation techniques (TA + Gallie and TA + hook) were compared with atlas lateral mass screws in the atlas combined with isthmic screws in axis. The modified C1 laminar hook combined with C1-2 TA screws and bone graft fixation provided the best biomechanical stability. The C1 lateral mass screws in the atlas combined with isthmic screws in axis fixation is a sound alternative when the C1-2 TA screw fixation is not feasible.

Inhibitive Effects of Alkyl Gallates on Hyaluronidase and Collagenase

A series of the gallate esters of n-alkanols (C(1)-C(12)) was examined to determine their inhibitory activities against hyaluronidase and collagenase. Hexyl, heptyl, octyl, nonyl, and decyl gallates inhibited both hyaluronidase and collagenase, and the most potent inhibitor was octyl gallate against both enzymes. Octyl 3,5-dihydroxybenzoate showed inhibitory effects on hyaluronidase, whereas collagenase was inhibited by octyl 3,4-dihydroxybenzoate.

Stereoselective synthesis of the C1–C12 fragment of the thuggacins

A concise asymmetric synthesis of the C1–C12 fragment of the antibacterial natural product thuggacins has been achieved. The stereochemistry of this fragment was established efficiently via stereoselective reduction and Evans-aldol condensation. Hanztsch’s method and a Horner–Wadsworth–Emmnons reaction were employed for thiazole formation and the construction of the E-α,β-unsaturated double bond.

Synthesis of the C1–C12 acid fragment of amphidinolide T marine macrolides via SmI 2-mediated enantioselective reductive coupling of aldehydes with a chiral crotonate

A new strategy for enantioselective assembly of the trisubstituted tetrahydrofuran ring has been established for synthesis of the C1–C12 acid fragment of amphidinolide T series marine macrolides. The key steps involve the SmI 2-mediated highly enantioselective reductive coupling of an aldehyde with the (1 S,2 R)- N-methylephedrine-derived crotonate to form the cis-3,4-disubstituted γ-butyrolactone and the subsequent BF 3-mediated 1,3- anti-selective allylation of the five-membered-ring oxocarbenium ion with allyltrimethylsilane. The desired C1–C12 acid fragment was obtained in >25% overall yield via a 9-step sequence.

Genotypic characterization of hospitalEnterococcus faecalisstrains using multiple-locus variable-number tandem-repeat analysis

The level of genetic diversity and relationships between the specific genotypes and the distribution of virulence determinants among Enterococcus faecalis strains isolated from patients hospitalized in different wards of two hospitals were investigated. Fifty-six clinical strains of E. faecalis, isolated from patients hospitalized in the period of 1999-2004 in several wards in Wrocław (Poland), were analysed by multiple-locus variable-number tandem-repeat analysis (MLVA). Analysis of seven genomic loci identified 40 novel genotypes among the analysed E. faecalis strains, with two major genomic groups, designated I and II, distinguished at a cut-off of 35%. With a similarity cut-off of 85.7%, the genotypes could be combined into 12 clusters (C1-C12), containing at least two isolates. The remaining 18 MLVA types were represented by a single isolate. Based on the data obtained by MLVA, it was found that (i) many E. faecalis isolates recovered from patients from the wards whose location allowed the potential transmission of micro-organisms, belonged to closely related MLVA types and (ii) possible relationships between specific E. faecalis genotype and the virulence factors lipase, haemolysin and esp gene can exist. Our study confirms that MLVA is a suitable method for the epidemiological study of E. faecalis and for the first time shows possible relationships between specific genotypes and such virulence determinants, i.e. lipase, haemolysin and esp gene.

Fuel dependence of benzene pathways

The relative importance of formation pathways for benzene, an important precursor to soot formation, was determined from the simulation of 22 premixed flames for a wide range of equivalence ratios (1.0–3.06), fuels (C1–C12), and pressures (20–760torr). The maximum benzene concentrations in 15 out of these flames were well reproduced within 30% of the experimental data. Fuel structural properties were found to be critical for benzene production. Cyclohexanes and C3 and C4 fuels were found to be among the most productive in benzene formation; and long-chain normal paraffins produce the least amount of benzene. Other properties, such as equivalence ratio and combustion temperatures, were also found to be important in determining the amount of benzene produced in flames. Reaction pathways for benzene formation were examined critically in four premixed flames of structurally different fuels of acetylene, n-decane, butadiene, and cyclohexane. Reactions involving precursors, such as C3 and C4 species, were examined. Combination reactions of C3 species were identified to be the major benzene formation routes with the exception of the cyclohexane flame, in which benzene is formed exclusively from cascading fuel dehydrogenation via cyclohexene and cyclohexadiene intermediates. Acetylene addition makes a minor contribution to benzene formation, except in the butadiene flame where C4H5 radicals are produced directly from the fuel, and in the n-decane flame where C4H5 radicals are produced from large alkyl radical decomposition and H atom abstraction from the resulting large olefins.

Enantioselective Synthesis of Oasomycin A (I). Part 1. Synthesis of the C1—C12 and C13—C28 Subunits.

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Synthesis of the C1–C12 fragment of amphidinolide T1

A synthesis of the C1–C12 fragment of amphidinolide T1 utilising Evans’ aldol, oxy-Michael and cross metathesis reactions as the key steps is described.

Enantioselective Synthesis of Oasomycin A, Part III: Fragment Assembly and Confirmation of Structure

Herein we address the total synthesis of the natural product oasomycin A by assembly of the C1–C12, C13–C28, and C29–C46 subunits, whose syntheses have been described in the preceding Communications. The synthesis plan (Scheme 1) incorporates a speculative late-stage macrolactonization of the linear seco acid precursor to form a 42-membered lactone that upon global deprotection would provide the natural product. Since oasomycin A is known to rearrange to the oasomycins D and E under basic conditions, an acid-mediated global deprotection was obligatory. It was our intention to assemble the requisite seco acid by using an aldol addition of the C1–C28 ketone I to the C29–C46 aldehyde II with a concomitant installation of the C29 stereocenter, followed by a stereoselective reduction of the C27 ketone. The assembly of ketone I through a Kocienski–Julia olefination of the C13–C28 aldehyde III with C1–C12 fragment IV was undertaken first (Scheme 2). Sulfone 1 was selectively deprotonated with KHMDS and treated with aldehyde 2 to afford the coupling product 3a as a 7:1 mixture of E/Z isomers (57% yield). In addition, a significant amount of a by-product was consistently formed in 15–25%

Enantioselective Synthesis of Oasomycin A, Part I: Synthesis of the C1–C12 and C13–C28 Subunits

Enantioselective Synthesis of Oasomycin A, Part I: Synthesis of the C1–C12 and C13–C28 Subunits