Leucine Methyl Ester Research Articles

Boost the Circularly Polarized Phosphorescence of Chiral Organometallic Platinum Complexes by Hierarchical Assembly into Fibrillar Networks.

Circularly polarized luminescence (CPL)-active molecular materials have drawn increasing attention due to their promising applications for next-generation display and optoelectronic technologies. Currently, it is challenging to obtain CPL materials with both large luminescence dissymmetry factor (glum) and high quantum yield (Φ). A pair of enantiomeric N N C-type Pt(II) complexes (L/D)-1 modified with chiral Leucine methyl ester are presented herein. Though the solutions of these complexes are CPL-inactive, the spin-coated thin films of (L/D)-1 exhibit giantly-amplified circularly polarized phosphorescences with |glum| of 0.53 at 560 nm and Φair of ~50 %, as well as appealing circular dichroism (CD) signals with the maximum absorption dissymmetry factor |gabs| of 0.37-0.43 at 480 nm. This superior CPL performance benefits from the hierarchical formation of crystalline fibrillar networks upon spin coating. Comparative studies of another pair of chiral Pt(II) complexes (L/D)-2 with a symmetric N C N coordination mode suggest that the asymmetric N N C coordination of (L/D)-1 are favorable for the efficient exciton delocalization to amplify the CPL performance. Optical applications of the thin films of (L/D)-1 in CPL-contrast imaging and inducing CP light generation from achiral emitters and common light-emitting diode lamps have been successfully realized.

Boost the Circularly Polarized Phosphorescence of Chiral Organometallic Platinum Complexes by Hierarchical Assembly into Fibrillar Networks

AbstractCircularly polarized luminescence (CPL)‐active molecular materials have drawn increasing attention due to their promising applications for next‐generation display and optoelectronic technologies. Currently, it is challenging to obtain CPL materials with both large luminescence dissymmetry factor (glum) and high quantum yield (Φ). A pair of enantiomeric N N C‐type Pt(II) complexes (L/D)‐1 modified with chiral Leucine methyl ester are presented herein. Though the solutions of these complexes are CPL‐inactive, the spin‐coated thin films of (L/D)‐1 exhibit giantly‐amplified circularly polarized phosphorescences with |glum| of 0.53 at 560 nm and Φair of ~50 %, as well as appealing circular dichroism (CD) signals with the maximum absorption dissymmetry factor |gabs| of 0.37–0.43 at 480 nm. This superior CPL performance benefits from the hierarchical formation of crystalline fibrillar networks upon spin coating. Comparative studies of another pair of chiral Pt(II) complexes (L/D)‐2 with a symmetric N C N coordination mode suggest that the asymmetric N N C coordination of (L/D)‐1 are favorable for the efficient exciton delocalization to amplify the CPL performance. Optical applications of the thin films of (L/D)‐1 in CPL‐contrast imaging and inducing CP light generation from achiral emitters and common light‐emitting diode lamps have been successfully realized.

Chiral polymer coatings on substrates via surface-initiated RAFT polymerization under ambient conditions

Surface-initiated reversible addition-fragmentation chain transfer polymerization using oxygen (O2-SI-RAFT) was performed to endow the substrates with chiral properties. Chiral monomers were synthesized using methacrylic anhydride and l/d-amino acids (phenylalanine methyl ester, alanine methyl ester, valine methyl ester, and leucine methyl ester), and chiral polymers were grown on titanium and glass substrates. The polymer brushes grafted from the substrates were confirmed by ellipsometry analysis, water contact angles, X-ray photoelectron spectroscopy, and atomic force microscopy. Block copolymer brushes were also polymerized through chain extension. Using a glass substrate, chirality of the polymer brushes grown on the surface could be confirmed via circular dichroism spectroscopy.

Supramolecular Assembly and Circularly Polarized Phosphorescence of Tridentate Platinum‐Isocyanide Complexes Modified with a Chiral Leucine Derivative

AbstractRecently, the exploration of circularly polarized luminescence (CPL)‐active materials has attracted extensive attention. Herein, a pair of enantiomeric tridentate platinum‐isocyanide complexes (D/L)‐5 decorated with a chiral leucine methyl ester are reported. The enhanced red phosphorescence and amplified CPL of (D/L)‐5 with a luminescent dissymmetric factor up to 0.008 and quantum yield of 67% are achieved via solution‐state aggregation, benefiting from the highly‐ordered nanobelt assembly as revealed by microscopic analyses. On the basis of the temperature‐dependent absorption, 2D NOESY NMR and powder X‐ray diffraction spectral investigations, these nanobelts are proposed to form via the cooperative assembly pathway with a head‐to‐tail molecular stacking. This work provides insight into the mechanism of supramolecular chirality amplification and important information for the design and synthesis of high‐performance CPL‐active materials.

Preliminary phytochemical screening, antimicrobial potentials and GC-MS analysis of Secamone afzelli Rhoem (Asclepiadaceae) leaves extracts

Secamone afzelli is used ethno-medicinally as remedies for stomach, colic and gastro-intestinal tract infections. This study screened the hexane, ethyl acetate and ethanol extracts of S. afzelli leaves for phytocompounds, antimicrobial activity and identified bioactive compounds in the most active extract using Gas Chromatography Mass Spectrometry (GC-MS) analysis. S. afzelli (200mg) leave was extracted by soxhlet apparatus using three solvents (hexane, ethyl acetate and ethanol) and the phytochemicals determined. Antimicrobial susceptibility and minimum inhibitory concentrations (MICs) was determined by agar-diffusion and agar-dilution methods respectively against selected resistant bacterial and fungal clinical isolates. The most active of the three crude extracts was analysed by GC-MS for bioactive compounds identification. Presence of carbohydrates, anthraquinone, glycosides, proteins, tannin, phenolic compounds and steroids were determined. The three extracts (hexane, ethyl acetate, and ethanol extracts) had antibacterial (Range of inhibition zone = 10 to 18 mm and MICs 12.5 to 200 mg/mL) but no antifungal activity. The ethanol extract was the most active with 29 bioactive compounds including piperazine, phytol, leucine methyl ester, N-methyl-N-(1-methylethyl)- 1Pentanamine, 7-propyl-pyrrolizin-1-thione and 4,5-dimethylnonane. The antibacterial activity and arrays of bioactive compounds detected in S. afzelli leaves suggest that the plant may be a good source of novel antimicrobial compounds.

Molecularly imprinted biomimetic surface plasmon resonance sensor for hormone detection

In this study, 17β-estradiol (E2) was performed by surface plasmon resonance (SPR) based on molecularly imprinted technique. In the first, SPR sensor was prepared by the formation of E2 imprinted poly(2-hydroxyetyl methacrylate) / (N-methacryloyl-(L)- leucine methyl esters) (PHEMALM) on the modified gold surface of SPR chip. Also, non-imprinted SPR chip was prepared by the same method at the E2 imprinted PHEMALM (E2-MIPHEMALM-SPR) chip without E2. E2-MIPHEMALM-SPR and non-imprinted (NIPHEMALM-SPR) chips were characterized with Fourier transform infrared spectrophotometry (FTIR), ellipsometry, atomic force microscopy (AFM) and contact angle measurements. After that, SPR chips were completed to SPR system to investigate kinetic properties for E2. The sensing ability of E2-MIPHEMALM-SPR chip was investigated with 20-10000 ng/mL concentrations of 17βestradiol solutions. The E2-MIPHEMALM-SPR chip was showed more selectivity for 17β-estradiol than NIPHEMALM-SPR chip. To show the selectivity of E2-MIPHEMALM-SPR chip competitive adsorption of 17β-estradiol, cholesterol and stigmasterol were investigated. E2-MIPHEMALM-SPR chip was investigated ten times with same concentrations of 17β-estradiol solution to show reuse of the chip. The results showed that the E2-MIPHEMALM-SPR chip has high selectivity for 17β-estradiol.

Thioesterase-Catalyzed Aminoacylation and Thiolation of Polyketides in Fungi.

Fungal highly reducing polyketide synthases (HRPKSs) biosynthesize polyketides using a single set of domains iteratively. Product release is a critical step in HRPKS function to ensure timely termination and enzyme turnover. Nearly all of the HRPKSs characterized to date employ a separate thioesterase (TE) or acyltransferase enzyme for product release. In this study, we characterized two fungal HRPKSs that have fused C-terminal TE domains, a new domain architecture for fungal HRPKSs. We showed that both HRPKS-TEs synthesize aminoacylated polyketides in an ATP-independent fashion. The KU42 TE domain selects cysteine and homocysteine and catalyzes transthioesterification using the side-chain thiol group as the nucleophile. In contrast, the KU43 TE domain selects leucine methyl ester and performs a direct amidation of the polyketide, a reaction typically catalyzed by nonribosomal peptide synthetase (NRPS) domains. The characterization of these HRPKS-TE enzymes showcases the functional diversity of HRPKS enzymes and provides potential TE domains as biocatalytic tools to diversify HRPKS structures.

Evaluating the impacts of amino acids in the second and outer coordination spheres of Rh-bis(diphosphine) complexes for CO2 hydrogenation.

To explore the influence of a biologically inspired second and outer coordination sphere on Rh-bis(diphosphine) CO2 hydrogenation catalysts, a series of five complexes were prepared by varying the substituents on the pendant amine in the P(Et)2CH2NRCH2P(Et)2 ligands (PEtNRPEt), where R consists of methyl ester modified amino acids, including three neutral (glycine methyl ester (GlyOMe), leucine methyl ester (LeuOMe), and phenylalanine methyl ester (PheOMe)), one acidic (aspartic acid dimethyl ester (AspOMe)) and one basic (histidine methyl ester (MeHisOMe)) amino acid esters. The turnover frequencies (TOFs) for CO2 hydrogenation for each of these complexes were compared to those of the non-amino acid containing [Rh(depp)2]+ (depp) and [Rh(PEtNMePEt)2]+ (NMe) complexes. Each complex is catalytically active for CO2 hydrogenation to formate under mild conditions in THF. Catalytic activity spanned a factor of four, with the most active species being the NMe catalyst, while the slowest were the GlyOMe and the AspOMe complexes. When compared to a similar set of catalysts with phenyl-substituted phosphorous groups, a clear contribution of the outer coordination sphere is seen for this family of CO2 hydrogenation catalysts.

In silico Description of LAT1 Transport Mechanism at an Atomistic Level.

The molecular mechanism of transport mediated by LAT1, a sodium-independent antiporter of large neutral amino acids, was investigated through in silico procedures, specifically making reference to two transported substrates, tyrosine (Tyr) and leucine methyl ester (LME), and to 3,5-diiodo-L-tyrosine (DIT), a well-known LAT1 inhibitor. Two models of the transporter were built by comparative modeling, with LAT1 either in an outward-facing (OF) or in an inward-facing (IF) conformation, based, respectively, on the crystal structure of AdiC and of GadC. As frequently classic Molecular Dynamics (MD) fails to monitor large-scale conformational transitions within a reasonable simulated time, the OF structure was equilibrated for 150 ns then processed through targeted MD (tMD). During this procedure, an elastic force pulled the OF structure to the IF structure and induced, at the same time, substrates/inhibitor to move through the transport channel. This elastic force was modulated by a spring constant (k) value; by decreasing its value from 100 to 70, it was possible to comparatively account for the propensity for transport of the three tested molecules. In line with our expectations, during the tMD simulations, Tyr and LME behaved as substrates, moving down the transport channel, or most of it, for all k values. On the contrary, DIT behaved as an inhibitor, being (almost) transported across the channel only at the highest k value (100). During their transit through the channel, Tyr and LME interacted with specific amino acids (first with Phe252 then with Thr345, Arg348, Tyr259, and Phe262); this suggests that a primary as well as a putative secondary gate may contribute to the transport of substrates. Quite on the opposite, DIT appeared to establish only transient interactions with side chains lining the external part of the transport channel. Our tMD simulations could thus efficiently discriminate between two transported substrates and one inhibitor, and therefore can be proposed as a benchmark for developing novel LAT1 inhibitors of pharmacological interest.

Ethyl phosphoramidates of acyclovir: design, synthesis, molecular docking (HN Protein), and evaluation of antiviral and antioxidant activities

Synthesis of a series of new ethyl phosphoramidates 9a–j of acyclovir through phosphorylation of hydroxy group followed by substitution of numerous amines/amino acid esters 7a–j was accomplished. The structures of newly synthesized compounds were elucidated by spectroscopic data such as IR, NMR (1H, 13C, and 31P) and mass spectrophotometery, and elemental analyses. The synthesized products were screened for their antiviral activity against Newcastle disease virus, antioxidant potency by α, α-diphenyl-β-picrylhydrazyl free radical scavenging and nitric oxide radical scavenging methods, and antioxidant capacity by Ferric reducing antioxidant power method. The compound bearing 1-hydroxy 2-butylamine, 9c and amino acid ester derivatives, bonded with leucine methyl ester 9h and tyrosine methyl ester 9j were found to be potent inhibiters of Newcastle disease virus than that of acyclovir drug. The compounds, 9c (IC50 value, 22.5 ± 1.00 μg/mL), 9i (IC50 value, 21.5 ± 1.00 μg/mL) and 9j (IC50 value, 19.0 ± 1.50 μg/mL) were exhibited promising antioxidant activity while other compounds displayed moderate to good antioxidant activity. Docking study using molecular docking environment into haemaglutinin–neuraminidase protein has been carried out to find the potential selectivity and binding orientation of these new compounds into protein binding site. Interestingly, all the title compounds except 9a and 9g docked well into HN protein with considerable binding affinities better than that of acyclovir drug.

ChemInform Abstract: Development of a Direct Photocatalytic C—H Fluorination for the Preparative Synthesis of Odanacatib.

AbstractA one‐step photocatalytic fluorination of (S)‐leucine methyl ester (I) is thoroughly elaborated which allows for the multi‐gram preparation of (S)‐γ‐fluoroleucine methyl ester (II) under continuous flow conditions, thus representing a straightforward access to the critical intermediate (II) of odanacatib (III).

Development of a Direct Photocatalytic C-H Fluorination for the Preparative Synthesis of Odanacatib.

Late-stage C-H fluorination is an appealing reaction for medicinal chemistry. However, the application of this strategy to process research appears less attractive due to the formation and necessary purification of mixtures of organofluorines. Here we demonstrate that γ-fluoroleucine methyl ester, an intermediate critical to the large-scale synthesis of odanacatib, can be accessed directly from leucine methyl ester using a combination of the decatungstate photocatalyst and N-fluorobenzenesulfonimide in flow. This efficient C-H fluorination reaction compares favorably with several generations of classical γ-fluoroleucine process syntheses.

Comparative Studies on Enantiomer Resolution of α-Amino Acids and Their Esters Using (18-Crown-6)-tetracarboxylic acid as a Chiral Crown Ether Selector by NMR Spectroscopy and High-Performance Liquid Chromatography

In a previous study, our group and the Machida group have developed covalently bonded and/or dynamically coated chiral stationary phases (CSPs) derived from (+)-(18crown-6)-2,3,11,12-tetracarboxylic acid (18-C-6-TA) for HPLC studies (Figure 1). These CSPs have been effectively applied in resolving several amino acids and various primary amino compounds. In addition, our group reported that 18-C-6-TA as an NMR chiral solvating agent is quite efficient to resolve some amino acid analytes in NMR spectroscopy. Therefore, we reported that the chiral crown ether selector 18-C-6-TA is useful for the enantiodiscrimination of phenylglycine, alanine, and diphenylalanine by NMR spectroscopy. Also other groups have reported some results using 18-C-6-TA as a chiral NMR solvating agent. Even though each analytical method by HPLC and NMR spectroscopy has been independently studied, the direct comparative study for enantiomer resolution of αamino acids and their esters using 18-C-6-TA as a chiral selector by two analytical methods has not been published. Especially, the enantiomer resolution results of two α-amino acids esters by NMR spectroscopy were only reported in our group. Therefore, in this study, we investigate the enantiomer resolution of various α-amino acids and their esters using (+)-18-C-6-TA as a chiral crown ether selector in NMR studies and compare these NMR results with liquid chromatographic resolution results obtained using 18-C-6TA derived CSP (CSP 1, Figure 1). Tables 1 and 2 show comparative results for the enantiomer resolution of several amino acids and their esters by NMR and HPLC. All investigated amino acids and esters were well resolved on CSP 1 derived from (+)-18-C-6-TA by HPLC (α = 1.18-2.74), except for leucine methyl ester and phenylalanine methyl ester (entries 2 and 3 in Table 2). However, all analytes including these two analytes showed chemical shift differences for the α-proton in the presence of 18-C-6-TA by NMR spectroscopy. It means that 18-C-6-TA successfully discriminated all tested amino acids and esters in this study by NMR. Typical H NMR spectra of valine (Val) and phenylalanine methyl ester (Phe-OMe) in the

고성능 액체 크로마토그래피에서 키랄 크라운 에테르로부터 유도된 키랄 고정상을 이용한 광학분리의 비교

Comparative liquid chromatographic enantiomer separation of α-amino acids, their esters and primary amino compounds was performed using two chiral stationary phases (CSPs) prepared by covalently bonding (+)-(18-crown-6)- 2,3,11,12-tetracarboxylic acid (18-C-6-TA) of the same chiral selector. In general, the separation factors and resolution factors for these analytes on CSP 1 were greater than on CSP 2, while these capacity factors on CSP 2 were quite greater than on CSP 1. Except for leucine methyl ester and phenylalanine methyl ester, the elution orders of all analytes including α- amino α-alkyl acids and phenylglycine alkyl esters on CSP 1 are identical to those on CSP 2. This study showed that different connecting structures for these two CSPs might influence their ability to resolve the analytes depending on their structures related to the chiral recognition mechanism.

Mass spectrometric behavior of functionalized calix[4]arenes: the screening ability of host–guest complex formation with amino acid methyl esters

The ESI–MS and MS/MS behavior of functionalized calix[4]arenes (1–5) has been studied in both positive and negative-ion mode. Liquid chromatography coupled to ESI–MS has been successfully used for separation of the byproducts issuing from the functionalization pathways, through the application of a simple reversed phase mechanism. The ability of (1–5) to host methyl esters of amino acids, tyrosine, tryptophan, phenylalanine, cysteine, valine, serine, leucine, isoleucine, and threonine has been evaluated by means of MS identification of the host–guest resulting in protonated molecular ions. The direct infusion within the ESI source of the solutions containing the two partners (i.e., calixarene and amino acid derivative) could act as a fast screening means for the evaluation of hosting capability. Only positive ionization may offer information about the host–guest complexes being formed. The influence of the excess of a partner in the infused solution strongly alters ionization yields, making quantitative approaches meaningless. Attempts to chromatographically isolate the host–guest complexes failed, probably due to the fact that interactions of the partners with the mobile and stationary phases are higher than the inclusion interactions. Structures consisting of combined fragments of the host–guest partners resulting from the collisional induced dissociation have not been observed.

ChemInform Abstract: Reactions of Fluorobenzene Tricarbonylchromium Complexes with Anions from Schiff Bases of α-Amino Esters; Enantioselective Synthesis of α-Aryl Amino Acids.

Abstract We report here a convenient synthesis of α-substituted aryl amino acids via the addition of α-amino esters to fluorobenzene tricarbonylchromium complexes. Optically pure α-aryl amino acids have been prepared by enantioselective substitution of fluorobenzene complexes using Schiff bases of L-alanine, leucine and valine methyl esters and (1R,2R,5R)-2-hydroxypinan-3-one.

Reversal of Stereoselectivity in the Cu-Catalyzed Conjugate Addition Reaction of Dialkylzinc to Cyclic Enone in the Presence of a Chiral Azolium Compound

Reversal of enantioselectivity in a Cu-catalyzed asymmetric conjugate addition reaction of dialkylzinc to cyclic enone with use of the same chiral ligand was successfully achieved. The reaction of 2-cyclohexen-1-one (30) with Et(2)Zn catalyzed by Cu(OTf)(2) in the presence of an azolium salt derived from a chiral beta-amino alcohol gave (S)-3-ethylcyclohexanone (31) in good enantioselectivity. Among a series of chiral azolium compounds examined, the benzimidazolium salt (10) having both a tert-butyl group at the stereogenic center and a benzyl substituent at the azolium ring was found to be the best choice of ligand in the Cu(OTf)(2)-catalyzed reaction. Good enantioselectivity was observed when the reaction was conducted by employing a benzimidazolium derivative rather than an imidazolium derivative. The influence of the substituent at the azolium ring on the stereoselectivity of the reaction was also examined. In addition, from the results of the reaction catalyzed by Cu(OTf)(2) combined with an azolium compound derived from (S)-leucine methyl ester, it was found that the hydroxy side chain in the chiral ligand is probably crucial for the enantiocontrol of the conjugate addition reaction. On the other hand, it was discovered from a screening test of copper species that the reversal of enantioselectivity was realized by allowing 30 to react with Et(2)Zn in the presence of Cu(acac)(2) combined with the same ligand precursor to afford (R)-31 as a major product. The influence of the stereodirecting group at the chiral ligand on the stereoselectivity in the Cu(acac)(2)-catalyzed reaction differed completely from that observed in the Cu(OTf)(2)-catalyzed reaction. Reaction with a cyclic enone consisting of a seven-membered ring such as 2-cyclohepten-1-one (40) resulted in increasing the enantioselectivity of the reaction. Thus, treatment of 40 with Et(2)Zn catalyzed by Cu(OTf)(2) combined with a benzimidazolium salt produced the corresponding (S)-conjugate adduct in a 92:8 enantiomer ratio (er), while the Cu(acac)(2)-catalyzed reaction with the same ligand afforded (R)-product in a 9:91 er.

Stabilization of Amino Acid Derived Diblock Copolymer Micelles through Favorable d:l side chain interactions

Optically pure N-acryloyl-(D)-leucine methyl ester (d-Leu-OMe) (1) and N-acryloyl-(L)-leucine methyl ester (l-Leu-OMe) (2) were synthesized and studied using infrared spectroscopy and melting point analysis to determine if d−l interactions are preferential relative to d−d or l−l interactions. Reversible addition−fragmentation chain transfer (RAFT) polymerization yielded enantiopure homopolymers of d-Leu-OMe (1) and l-Leu-OMe ester (2). The two enantiopure polymers, 5 and 6, and a 1:1 w/w racemic blend of both polymers were studied using infrared spectroscopy to investigate the intermolecular interactions in the polymeric systems. Poly(tert-butyl acrylate) [P(tBuA)] macro chain transfer agents were used to synthesize two diblock copolymers from 1 and 2, respectively. Subsequent deprotection of the P(tBuA) block to poly(acrylic acid) (PAA) yielded two chiral amphiphilic diblock copolymers, 7 and 8. Both enantiopure polymers were self-assembled separately and then in a 1:1 w/w ratio, and the resulting morphologies characterized using dynamic light scattering, atomic force microscopy, transmission electron microscopy, and circular dichroism.

Human T cell responses to β-galactosidase

The peripheral blood of most normal individuals has been shown to contain T cells that respond to beta-galactosidase (beta-Gal), presumably as a result of natural priming. Three T cell clones (clones 1,2,4) specific for beta-Gal were isolated from peripheral blood mononuclear cells (PBMC) after pretreatment with leucine methyl ester (LeuOMe); a fourth clone from the same individual was isolated from untreated cells. All four clones were CD4+ CD8- alpha beta TcR+ and clone 1 was additionally shown to be cytotoxic. Epstein-Barr virus (EBV) transformed B cell lines were derived from LeuOMe-treated or untreated PBMC and used to study the efficiency of presentation of beta-Gal to one of the clones. The results indicated that B cells transformed after LeuOMe treatment presented beta-Gal at lower concentrations than untreated controls. beta-Gal would therefore appear to be a highly suitable model antigen for studies of immunoregulation in humans.

A Solid State Polymer‐Coated Electrode Containing a Chiral Crown Ether Derivative for Enantioselective Detection of Phenylglycine Methyl Ester Isomer

AbstractAll solid‐state enantioselective electrode (ASESE) based on a newly synthesized chiral crown ether derivative ((R)‐(−)‐(3,3′‐diphenyl‐1,1′‐binaphthyl)‐23‐crown‐6 incorporating 1,4‐dimethoxybenzene) was prepared and characterized by potentiometry. The ASESE clearly showed enantiomer discrimination for methyl esters of alanine, leucine, valine, phenylalanine, and phenylglycine, where the enantioselectivity for phenylglycine methyl ester was the highest (KR,S=8.5±7.1%). Experimental parameters of ASESE for the analysis of (R)‐(−)‐phenylglycine methyl ester were optimized. The optimized ASESE showed a slope of 55.3±0.2 mV/dec for (R)‐(−)‐phenylglycine methyl ester in the concentration range of 1.0×10−5–1.0×10−2 M and the detection limit was 9.0×10−6 M. The ASESE showed good selectivity for (R)‐(−)‐phenylglycine methyl ester against inorganic cations and various amino acid methyl esters. The concentration of (R)‐(−)‐phenylglycine methyl ester was determined in the mixture of (R)‐(−) and (S)‐(+)‐phenylglycine methyl ester, which ratios varied from 2 : 1 to 1 : 9. The lifespan of the electrode was alleged to be 30 days.