Chiral Discrimination by Ionic Liquids: Impact of Ionic Solutes

Chiral ionic liquids hold promise in many asymmetric applications. This study explores the impact of ionic solutes on the chiral discrimination of five amino acid methyl ester‐based ionic liquids, including L‐ and D‐alanine methyl ester, L‐proline methyl ester, L‐leucine methyl ester, and L‐valine methyl ester cations combined with bis(trifluoromethanesulfonimide) anion. Circularly polarized luminescence spectroscopy was used to study the chiral discrimination by measuring the racemization equilibrium of a dissymmetric europium complex, Eu(dpa)₃^3? (where dpa = 2,6‐pyridinedicarboxylate). The chiral discrimination measured was dependent on the concentration of Eu(dpa)₃^3? and this concentration‐dependence was different in each of the ionic liquids. Ionic liquids with L‐leucine methyl ester and L‐valine methyl ester even switched enantiomeric preference based on the solute concentration. Changing the cation of the Eu(dpa)₃^3? salt from tetrabutylammonium to tetramethylammonium ion also affected the chiral discrimination demonstrated by the ionic liquids. Chirality 27:320–325, 2015. © 2015 Wiley Periodicals, Inc.     

Engineering of Ralstonia eutropha H16 for Autotrophic and Heterotrophic Production of Methyl Ketones

Ralstonia eutropha is a facultatively chemolithoautotrophic bacterium able to grow with organic substrates or H₂ and CO₂ under aerobic conditions. Under conditions of nutrient imbalance, R. eutropha produces copious amounts of poly[(R)-3-hydroxybutyrate] (PHB). Its ability to utilize CO₂ as a sole carbon source renders it an interesting new candidate host for the production of renewable liquid transportation fuels. We engineered R. eutropha for the production of fatty acid-derived, diesel-range methyl ketones. Modifications engineered in R. eutropha included overexpression of a cytoplasmic version of the TesA thioesterase, which led to a substantial (>150-fold) increase in fatty acid titer under certain conditions. In addition, deletion of two putative β-oxidation operons and heterologous expression of three genes (the acyl coenzyme A oxidase gene from Micrococcus luteus and fadB and fadM from Escherichia coli) led to the production of 50 to 65 mg/liter of diesel-range methyl ketones under heterotrophic growth conditions and 50 to 180 mg/liter under chemolithoautotrophic growth conditions (with CO₂ and H₂ as the sole carbon source and electron donor, respectively). Induction of the methyl ketone pathway diverted substantial carbon flux away from PHB biosynthesis and appeared to enhance carbon flux through the pathway for biosynthesis of fatty acids, which are the precursors of methyl ketones.     

Abortifacient action of orally administered 16, 16 dimethyl prostaglandin E2 and its methyl ester

16, 16 dimethyl Prostaglandin E₂ (Free acid and methyl ester) administered orally have a stimulant effect on the pregnant human uterus. Pregnancy was terminated in twelve out of twenty women by two hourly oral doses of 100μg of these analogues The relatively high incidence of gastrointestinal side effects — nausea, vomitting and diarrhoea — would tend to limit the usefulness of orally administered 16, 16 dimethyl PGE₂ and its methyl ester as abortifacients.     

Synthetic transformations of higher terpenoids. XXVI. 16-acetylaminomethyllabdanoids and their cytotoxicity

Coupling of methyl 16-aminomethyllambertianate with N-Boc-protected ω-amino acids resulted in 16-(N-Boc-aminononan)- and 16-(N-Boc-aminoundecan)amidomethyllabdanoids. Interaction of methyl aminomethyllambertianate with bicyclo[2.2.1]hept-5-en-2,3-dicarboxylic acid anhydride led to the amide of bicyclo[2.2.1]heptan-1,2-dicarboxylic acid with a labdanoid substituent. Reaction of methyl 16-aminomethyllambertianate with chloroacetyl chloride resulted in methyl 16-(chloroacetylaminomethyl)lambertianate; coupling of the latter with methyl esters of amino acids gave the corresponding amides of methyl lambertianate. The compounds obtained were more cytotoxic toward CEM-13, MT-4, and U-937 tumor cell lines as compared with lambertianic acid; the dose inhibiting tumor cell viability by 50% (CCID₅₀) of the more active compounds was 3.9–9.9 μM.     

Synthesis of (±)-16-thioketal and 16-keto prostaglandins

The synthesis of ((±)-16-thioketal and 16-keto PGE₂ methyl ester ( and ) is herein described.     

Synthesis of methyl 16-trideuteriohexadecanoate

Methyl 16-trideuteriohexadecanoate has been prepared in high isotopic purity and in 29% overall yield, from methyl 7-oxo-16-heptadecenoate. The oxo group was reduced with sodium cyanoborohydride and the CD₃ group was introduced by reduction with lithium aluminum deuteride, first of the ester group to the alcohol and then of the derived mesylate. The carboxyl group was formed by oxidative cleavage of the double bond.     

Methyl chloride metabolism of the strictly anaerobic,methyl chloride-utilizing homoacetogen strain MC

The methyl chloride metabolism of the homoacetogenic, methyl chloride-utilizing strain MC was investigated with cell extracts and cell suspensions of the organism. Cell extracts were found to contain all enzyme activities required for the conversion of methyl chloride or of H₂ plus CO₂ to acetate. They catalyzed the dechlorination of methyl chloride with tetrahydrofolate as the methyl acceptor at a rate of 20 nmol/min × mg of cell protein. Also, the O-demethylation of vanillate with tetrahydrofolate could be measured at a rate of 40 nmol/min × mg. Different enzyme systems appeared to be responsible for the dehalogenation of CH₃Cl and for the O-demethylation of methoxylated aromatic compounds, since cells grown with methoxylated aromatic compounds exhibited a significantly lower activity of CH₃Cl conversion than methyl chloride grown cells and vice versa. In addition, ammonium thiocyanate (5 mM) completely inhibited CH₃Cl dechlorination, whereas the consumption of vanillate was not affected significantly. The data were taken to indicate, that the methyl chloride dehalogenation is catalyzed by a specific, inducible enzyme present in strain MC, and that tetrahydrofolate rather than the corrinoid-protein involved in acetate formation is the primary acceptor of the methyl group in the dechlorination reaction.     

Biodegradation of Methyl Ethyl Ketone and Methyl Isopropyl Ketone in a Composite Bead Biofilter

Biodegradation of methyl ethyl ketone (MEK) and methyl isopropyl ketone (MIPK) in a composite bead biofilter was investigated. The composite bead represents a spherical PVA/peat/KNO₃/GAC one. Both the microbial growth rate μ and the biochemical reaction rate coefficient k_d could be affected with increasing inlet concentration. For the microbial growth process, an inhibitory effect of almost the same sensitivity for the two ketone compounds and the μ value of MEK was more pronounced than that of MIPK in the inlet concentration range of 100 to 300 ppm. The half‐saturation constant K_s values of MEK and MIPK were 21.56 and 22.96 ppm, respectively. The maximum reaction rate V_m values of MEK and MIPK were 9.06 and 7.55 g C/h kg of packed material, respectively. Zero‐order kinetics with diffusion limitation could be regarded as the most adequate biochemical reaction model. For the biochemical process, the inhibitory effect for MEK was more notable than that for MIPK in the inlet concentration range of 100 to 150 ppm whereas it was the reverse in the inlet concentration range of 150 to 300 ppm. The k_d value of MEK was greater than that of MIPK in the inlet concentration range of 100 to 300 ppm. The maximum elimination capacities of MEK and MIPK were found to be 44.2 and 35.2 g C/h m³ of bed volume. MEK, in particular the compound with a lower number of carbons or no side groups in the main chain, was easier biodegraded by the microorganisms than MIPK.     

Structures of the Metabolites from Steviol Methyl Ester by Gibberella fujikuroi

Steviol methyl ester (methyl ent-13-hydroxykaur-16-en-19-oate)* was converted into five new metabolites together with a known compound, methyl ent-7α,13-dihydroxykaur-16-en-19-oate, by Gibberella fujikuroi in the presence of a plant growth retardant. The structures of these new metabolites were elucidated to be methyl ent-7β,13-dihydroxykaur-16-en-19-oate, methyl ent-11α,13-dihydroxykaur-16-en-19-oate, methyl ent-7β,11α,13-trihydroxykaur-16-en-19-oate, methyl ent-11α, 13,15β-trihydroxykaur-16-en-19-oate and methyl ent-13,15β-dihydroxy-11-oxokaur-16-en-19-oate mainly by spectroscopic analyses.     

PMR analysis of alkenoic esters using shift reagents

The use of the deuterated shift reagent, Eu(FOD) ₃-d₃₀, has enabled an identification to be made of the 8- to 12-isomers of methyl trans-octadecenoate from PMR measurements at 100 or 220 MHz. The δ-values observed were in good agreement with those calculated from a method employing the lanthanide-induced shifts (LIS) in methyl stearate and the deshielding effects of the double bond. Use was made of the δ-value of the methyl ester absorption as an internal reference to allow corrections to be made for changes in measuring conditions. It is concluded that all positional isomers of both cis and trans methyl octadecenoates may be identified by this method.     

Screening of in Vitro Inhibition of Lactoperoxidase Enzyme by Methyl Benzoate Derivatives with Molecular Docking Studies

Lactoperoxidase enzyme (LPO) is secreted from salivary, mammary, and other mucosal glands including the bronchi, lungs, and nose, which had functions as a natural and the first line of defense towards viruses and bacteria. In this study, methyl benzoates were examined in LPO enzyme activity. Methyl benzoates are used as precursors in the synthesis of aminobenzohydrazides used as LPO inhibitors. For this purpose, LPO was purified in a single step using sepharose-4B-l-tyrosine-sulfanilamide affinity gel chromatography with a yield of 9.91 % from cow milk. Also, some inhibition parameters including the half maximal inhibitory concentration (IC₅₀) value and an inhibition constant (K_i) values of methyl benzoates were determined. These compounds inhibited LPO with K_i values ranging from 0.033±0.004 to 1540.011±460.020 μM. Compound 1 a (methyl 2-amino-3-bromobenzoate) showed the best inhibition (K_i=0.033±0.004 μM). The most potent inhibitor ( 1 a ) showed with a docking score of −3.36 kcal/mol and an MM-GBSA value of −25.05 kcal/mol, of these methyl benzoate derivatives ( 1 a – 16 a ) series are established H-bond within the binding cavity with residues Asp108 (distance of 1.79 Å), Ala114 (distance of 2.64 Å), and His351 (distance of 2.12 Å).     

Synthesis and luminescence properties of novel 8‐hydroxyquinoline derivatives and their Eu(III) complexes

Six novel 8‐hydroxyquinoline derivatives were synthesized using 2‐methyl‐8‐hydroxyquinoline and para‐substituted phenol as the main starting materials, and were characterized by ¹H nuclear magnetic resonance (NMR), mass spectrometry (MS), ultraviolet (UV) light analysis and infra‐red (IR) light analysis. Their complexes with Eu(III) were also prepared and characterized by elemental analysis, molar conductivity, UV light analysis, IR light analysis, and thermogravimetric–differential thermal analysis (TG–DTA). The results showed that the ligand coordinated well with Eu(III) ions and had excellent thermal stability. The structure of the target complex was EuY^1–6(NO₃)₃.2H₂O. The luminescence properties of the target complexes were investigated, the results indicated that all target complexes had favorable luminescence properties and that the introduction of an electron‐donating group could enhance the luminescence intensity of the corresponding complexes, but the addition of an electron‐withdrawing group had the opposite effect. Among all the target complexes, the methoxy‐substituted complex (–OCH₃) had the highest fluorescence intensity and the nitro‐substituted complex (–NO₂) had the weakest fluorescence intensity. The results showed that 8‐hydroxyquinoline derivatives had good energy transfer efficiency for the Eu(III) ion. All the target complexes had a relatively high fluorescence quantum yield. The fluorescence quantum yield of the complex EuY³(NO₃)₃.2H₂O was highest among all target complexes and was up to 0.628. Because of excellent luminescence properties and thermal stabilities of the Eu(III) complexes, they could be used as promising candidate luminescent materials.     

Deodorizing Mechanism of (–)-Epigallocatechin Gallate against Methyl Mercaptan

The deodorizing mechanism of (-)-epigallocatechin gallate (EGCg), the main constituent of a green tea extract, against methyl mercaptan (CH₃SH) was investigated. EGCg showed deodorizing activity against CH₃SH by a chemical reaction between EGCg and CH₃SH. The non-volatile reaction products were identified to be compounds introducing a methylthio and/or a methylsulfinyl group into the B ring of EGCg, and gaseous oxygen was necessary for deodorizing activity. From these results, it was assumed that the deodorizing mechanism of EGCg was due to the addition of a methylthio group to the ortho-quinone generated by atmospheric oxygen. It was also found that secondary compounds produced by the reaction between EGCg and CH₃SH had a stronger deodorizing activity than that of EGCg itself.     

Gas Chromatography Mass Spectrometric Analysis of Monohydro-peroxide Isomers and Their Secondary Oxidation Productsof Methyl Linoleate and Methyl Linolenate

Emulsions of methyl linoleate monohydroperoxides (18:2-monoHP) and methyl linolenate monohydroperoxides (18: 3-monoHP) were incubated with ferrous sulfate and ascorbic acid. Gas chromatography mass spectrometric analysis of the trimethylsilyl and te^butyldimethylsilyl derivatives of the reaction products showed that isomerization and secondary oxidation happen competitively during decomposition of 18:2-monoHP, while the secondary oxidation reaction proceeds preferentially and little isomerization is observed in 18: 3-monoHP. It is suggested that 18:3-monoHP is more susceptible to secondary oxidation than 18:2-monoHP because of 18:3 specific secondary oxidation resulting in hydroperoxy-cyclic peroxides and dihydroperoxides. Moreover, an experiment using ¹⁸0₂ has demonstrated that molecular oxygen is scrambled by isomerization and secondary oxidation. It was confirmed that molecular oxygen is attached preferentially to the C-13 position in the 9-monoHP isomer and C-9 position in the 13-monoHP isomer during degradation of 18:2-monoHP.     

Oxidation of Methyl Halides by the Facultative Methylotroph Strain IMB-1

Washed cell suspensions of the facultative methylotroph strain IMB-1 grown on methyl bromide (MeBr) were able to consume methyl chloride (MeCl) and methyl iodide (MeI) as well as MeBr. Consumption of >100 μM MeBr by cells grown on glucose, acetate, or monomethylamine required induction. Induction was inhibited by chloramphenicol. However, cells had a constitutive ability to consume low concentrations (<20 nM) of MeBr. Glucose-grown cells were able to readily oxidize [¹⁴C]formaldehyde to ¹⁴CO₂ but had only a small capacity for oxidation of [¹⁴C]methanol. Preincubation of cells with MeBr did not affect either activity, but MeBr-induced cells had a greater capacity for [¹⁴C]MeBr oxidation than did cells without preincubation. Consumption of MeBr was inhibited by MeI, and MeCl consumption was inhibited by MeBr. No inhibition of MeBr consumption occurred with methyl fluoride, propyl iodide, dibromomethane, dichloromethane, or difluoromethane, and in addition cells did not oxidize any of these compounds. Cells displayed Michaelis-Menten kinetics for the various methyl halides, with apparent K_s values of 190, 280, and 6,100 nM for MeBr, MeI, and MeCl, respectively. These results suggest the presence of a single oxidation enzyme system specific for methyl halides (other than methyl fluoride) which runs through formaldehyde to CO₂. The ease of induction of methyl halide oxidation in strain IMB-1 should facilitate its mass culture for the purpose of reducing MeBr emissions to the atmosphere from fumigated soils.     

Chloromethane, a Novel Methyl Donor for Biosynthesis of Esters and Anisoles in Phellinus pomaceus

Chloromethane (CH₃Cl), a gaseous natural product released as a secondary metabolite by many woodrotting fungi of the family Hymenochaetaceae, has been shown to act as a methyl donor for biosynthesis of methyl esters of benzoic and furoic acid in the primary metabolism of Phellinus pomaceus. The broad-specificity methylating system could esterify a wide range of aromatic and aliphatic acids. In addition to CH₃Cl, both bromo- and iodomethanes acted as methyl donors. Methylation did not appear to proceed via methanol or a coenzyme A intermediate. The initial growth-related accumulation of methyl benzoate during culture of P. pomaceus was paralleled by an increase in activity of the methylating system in the mycelium. Changes in percent incorporation of C²H₃ from exogenous C²H₃Cl during growth indicated that although utilization of CH₃Cl was initially closely coupled to biosynthesis of the compound, the system became less tightly channeled later in growth. This phase coincided with release of gaseous CH₃Cl by the fungus. A biochemically distinct CH₃Cl-utilizing system capable of methylating phenols and thiophenol was also identified in the fungus, but in contrast with the carboxylic acid-methylating system, it attained maximum activity in the idiophase. Preliminary investigations of a non-CH₃Cl-releasing fungus, Fomitopsis pinicola, have shown the presence of a CH₃Cl-utilizing system capable of methylating benzoic acid, suggesting that CH₃Cl biosynthesis may occur in non-hymenochaetaceous fungi. Halogenated compounds hitherto found in nature are mainly stable end products of metabolism. The participation of CH₃Cl in primary fungal metabolism demonstrates that some halometabolites may have a previously unrecognized role as intermediates in the biosynthesis of nonhalogenated natural products.     

Studies on the Origin of the Methyl Groups of Choline in Ochromonas malhamensis*

SYNOPSIS. Five- to 6-day-old resting cells of Ochromonas malhamensis were incubated at pH 6.5 with glucose and appropriate C¹⁴ precursors of the methyl groups of phospholipid-choline. Under the experimental conditions L-methionine-C¹⁴H₃ was the most efficient source of choline-methyl groups, followed by formate-C¹⁴, formaldehyde-C¹⁴ and DL-serine-3-C¹⁴, respectively. Glycine-2-C¹⁴ was not incorporated into choline. Both L-methionine-C¹⁴H₃ and formate-C¹⁴ served as precursors for the methyl groups of monomethylethanolamine, dimethylethanolamine and choline. Addition of non-radio-active L-methionine depressed the incorporation of formate-C¹⁴ into choline-methyl groups by 50%. The results support the hypothesis that methionine can be the source of all 3 methyl groups of choline, and that formate is probably converted to the methyl group of methionine before transmethylation to choline. However, an alternate pathway from single-carbon sources cannot be excluded.     

Separation of N-TFA-Glycyl and N-TFA-l-Prolyl Dipeptide Methyl Esters by Gas-chromatography

We have prepared a series of N-TFA-glycyl and N-TFA-l-prolyl dipeptide methyl ester from the corresponding dipeptide methyl esters by treating them with (TFA-Gly)₂O and TFA-l-Pro-Cl, respectively. Separation of these tripeptide derivatives by G.L.C. was studied and a relationship between the amino acid compositions of the tripeptides and their q_i-values (relative retention values) was observed, analogous to the case of the dipeptides previously reported.     

Methyl palmitate: a novel product of the Medfly (Ceratitis capitata) corpus allatum

The corpus allatum (CA) of adult female Ceratitis capitata produces methyl palmitate (MP) in vitro, in addition to JHB₃ and JH III. Biosynthesized MP migrates on TLC and co-elutes from RP-18 HPLC with synthetic MP. Its identity is verified herein by GCMS. MP production is up-regulated twofold by mevastatin, an inhibitor of mevalonic acid-dependent isoprene biosynthesis. Fosmidomycin, an inhibitor of mevalonic acid-independent isoprene synthesis in graminaceous plants, up-regulates MP synthesis by about fourfold. However, it does not depress JHB₃ biosynthesis concurrently. This suggests that the initial enzyme(s) in the conversion of 1-deoxy-xylulose 5-phosphate to isoprene is presumably present in C. capitata, but is inhibited by fosmidomycin, and this inhibition diverts precursors to MP synthesis. Phytol, an acyclic diterpene, might be suppressing isoprene biosynthesis by CA, thereby resulting in a fourfold increase in the MP biosynthesis. Linolenic acid is an end-product and its presence in incubation media up-regulates MP biosynthesis by twofold, presumably due to the feedback diversion to biosynthesis of C_16:0 and its methyl ester. Biosynthesis of MP is markedly depressed after mating, while otherwise maintained at significantly higher levels in virgin females. MP biosynthesis is significantly reduced in virgin females by direct axonal control but is less consistent after mating.     

Photoluminescence imaging of europium (III)‐doped γ‐Al2O3 nanofiber structures

Aluminium oxide (Al₂O₃) has widely been used for catalysts, insulators, and composite materials for diverse applications. Herein, we demonstrated if γ‐Al₂O₃ was useful as a luminescence support material for europium (Eu) (III) activator ion. The hydrothermal method and post‐thermal treatment at 800°C were employed to synthesize Eu(III)‐doped γ‐Al₂O₃ nanofibre structures. Luminescence characteristics of Eu(III) ions in Al₂O₃ matrix were fully understood by taking 2D and 3D‐photoluminescence imaging profiles. Various sharp emissions between 580 to 720 nm were assigned to the ⁵D₀→⁷F_J (J = 0, 1, 2, 3, 4) transitions of Eu(III) activators. On the basis of X‐ray diffraction crystallography, Auger elemental mapping and the asymmetry ratio, Eu(III) ions were found to be well doped into the γ‐Al₂O₃ matrix at a low (1 mol%) doping level. A broad emission at 460 nm was substantially increased upon higher (2 mol%) Eu(III) doping due to defect creation. The first 3D photoluminescence imaging profiles highlight detailed understanding of emission characteristics of Eu(III) ions in Al oxide‐based phosphor materials and their potential applications.