β‐Cyclodextrin‐Platinum Nanoparticles/Graphene Nanohybrids: Enhanced Sensitivity for Electrochemical Detection of Naphthol Isomers

Naphthol isomers, including α‐naphthol (α‐NAP) and β‐naphthol (β‐NAP), are used widely in various fields and are harmful to the environment and human health. The qualitative and quantitative determination of naphthol isomers is therefore of great significance. Herein, β‐cyclodextrin (β‐CD)‐platinum nanoparticles (Pt NPs)/graphene nanosheets (GNs) nanohybrids (β‐CD‐PtNPs/GNs) were prepared for the first time using a simple wet chemical method and characterized by atomic force microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and electrochemical methods, and then applied successfully in the ultrasensitive electrochemical detection of naphthol isomers. The results show that the oxidation peak currents of naphthol isomers obtained at the glassy carbon (GC) electrode modified with β‐CD‐PtNPs/GNs are much higher than those at the β‐CD/GNs/GC, PtNPs/GNs/GC, GNs/GC, and bare GC electrodes. Additionally, compared with other electrochemical sensors developed previously, the proposed electrode results in improved detection limits of about one order of magnitude for α‐NAP (0.23 nM ) and three orders of magnitude for β ‐NAP (0.37 nM ).     

One‐Step Synthesis of β‐Cyclodextrin Functionalized Graphene/Ag Nanocomposite and Its Application in Sensitive Determination of 4‐Nitrophenol

β‐Cyclodextrin functionalized graphene/Ag nanocomposite (β‐CD/GN/Ag) was prepared via a one‐step microwave treatment of a mixture of graphene oxide and AgNO₃. β‐CD/GN/Ag was employed as an enhanced element for the sensitive determination of 4‐nitrophenol. A wide linear response to 4‐nitrophenol in the concentration ranges of 1.0×10^?8–1.0×10^?7 mol/L, and 1.0×10^?7–1.5×10^?3 mol/L was achieved, with a low detection limit of 8.9×10^?10 mol/L (S/N=3). The mechanism and the heterogeneous electron transfer kinetics of the 4‐nitrophenol reduction were discussed according to the rotating disk electrode experiments. Furthermore, the sensing platform has been applied to the determination of 4‐nitrophenol in real samples.     

Supramolecular Assembly of β‐Cyclodextrin‐Capped Gold Nanoparticles on Ferrocene‐Functionalized ITO Surface for Enhanced Voltammetric Analysis of Ascorbic Acid

A supramolecular recognition functionalized electrode (βCD‐nanoAu/Fc‐ITO) which exhibits redox‐activity was prepared through supramolecular assembly of β‐cyclodextrin (βCD) capped gold nanoparticles (βCD‐nanoAu) on the ITO previously coated with a monolayer of ferrocene residues (Fc‐ITO). The immobilization of βCD‐nanoAu on Fc‐ITO was confirmed by atomic force microscopy (AFM), and the supramolecular nature of the immobilization approach was also confirmed by cyclic voltammetry. On the other hand, the electrocatalytic activity of βCD‐nanoAu/Fc‐ITO electrode was also studied. The electrocatalytic activity toward ascorbic acid (AA) was enhanced compared with that at the Fc‐ITO electrode, and a linear relationship existed between the anodic peak and the concentration of AA in the range of 5.3×10^?5 to 3.0×10^?3 M with a detection limit (S/N=3) of 4.1×10^?6 M.     

Molecular Recognition of Phenylalanine Enantiomers onto a Solid Surface Modified with Electropolymerized Pyrrole‐β‐Cyclodextrin Conjugate

We report the electrochemical deposition of a β‐cyclodextrin pyrrole conjugate (Py‐β‐CD) on an electrode surface including i) characterization based on surface‐enhanced Raman scattering and field‐emission scanning electron microscopy; ii) studies of the molecular recognition of enantiomers of phenylalanine methyl ester hydrochlorides (Phe) based on linear sweep voltammetry and a quartz crystal microbalance. The PPy‐β‐CD polymeric layer on a metallic substrate is distinguished by its inhomogeneity, in which both highly ordered β‐CD units and highly disordered polymer chains are observed. The voltammetric recognition results showed that PPy‐β‐CD exhibited a higher sensitivity for d ‐Phe (138±15)×10³ than for l ‐Phe (6±1)×10³ within the concentration range 0.1–0.75 mM (n=3) despite the differences in the polymer arrangement on the surface. A possible mechanism of molecular recognition of phenylalanine enantiomers is discussed.     

Synthesis and characterization of a poly(N‐isopropylacrylamide) with β‐cyclodextrin as pendant groups

A novel linear poly(N‐isopropylacrylamide) (PNIPA) with β‐cylodextrin (β‐CD) moiety (PNIPA‐β‐CD) was synthesized by the conjugation of β‐CD carrying amino groups (EDA‐β‐CD) onto PNIPA with epoxy groups (P(NIPA‐co‐GMA), M_n = 3.86 × 10⁴), and the related reaction conditions are investigated. PNIPA‐β‐CD was characterized by means of IR, NMR and UV spectroscopes, element analysis, and differential scanning calorimetry (DSC). The number‐average molecular weight (M_n) and the β‐CD content of the obtained PNIPA‐β‐CD are 4.87 × 10⁴ and 18.8 wt %, respectively. PNIPA‐β‐CD can not only respond to temperature stimuli but also include guest molecules. Lower critical solution temperature (LCST) of aqueous PNIPA‐β‐CD solution is similar to that of PNIPA. The association constant (K_a) for PNIPA‐β‐CD with methyl orange (MO) is 2.4 × 10³ L mol^?1 at pH 1.4, which is comparable to that of EDA‐β‐CD (K_a = 2.9 × 10³ L mol^?1). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3516–3524, 2005     

Use of cyclodextrin‐modified gold nanoparticles for enantioseparations of drugs and amino acids based on pseudostationary phase‐capillary electrochromatography

The application of chemical‐modified gold nanoparticles (GNPs) as chiral selector for the enantioseparation based on pseudostationary phase‐CEC (PSP‐CEC) is presented. GNPs modified by thiolated β‐CD were characterized by NMR and FT‐IR. The nanoparticle size was determined to be of 9.5 nm (+2.5 nm) by Transmission Electron Microscopy (TEM) and UV spectra. Four pairs of dinitrophenyl‐labeled amino acid enantiomers (DL‐Val, Leu, Glu and Asp) and three pairs of drug enantiomers (RS‐chlorpheniramine, zopiclone and carvedilol) were analyzed by using modified GNPs as the chiral selector in PSP‐CEC. Good theoretical plate number (up to 2.4×10⁵ per meter) and separation resolution (up to 4.7) were obtained even with low concentration of modified GNPs (0.8–1.4 mg/mL). The corresponding concentration of β‐CD in the buffer was only 0.30?0.53 mM, which was much lower than the optimum concentration of 15 mM if pure β‐CD was used as chiral selector. Our results showed that thiolated β‐CD modified GNPs have more sufficient interaction with the analytes, resulting in significant enhancement of enantioseparation. The study shed light on potential usage of chemical modified GNPs as chiral selector for enantioseparation based on PSP‐CEC.     

Studies on the non‐covalent interactions between cyclodextrins and aryl alkanol piperazine derivatives by mass spectrometry and fluorescence spectroscopy

The non‐covalent complexes of α‐ and β‐cyclodextrins (α‐, β‐CDs) with two aryl alkanol piperazine derivatives (Pipe I and Pipe II) have been studied by electrospray ionization mass spectrometry (ESI‐MS) and fluorescence spectroscopy. The ESI‐MS experimental results demonstrated that Pipe I can conjugate to β‐CD and form 1:1 or 1:2 stoichiometric non‐covalent complexes, and Pipe II can only form 1:1 complexes with α‐ or β‐CD. Fluorescence spectra indicated that the fluorescence intensities of Pipe I and Pipe II can be enhanced by increasing the content of β‐CD. The mass spectrometric titration experiments showed that the dissociation constants K_d1 were 5.77 and 9.52 × 10^?4 mol L^?1 for the complexes of α‐CD with Pipe I and Pipe II, respectively, revealing that the binding of α‐CD‐Pipe I was stronger than α‐CD‐Pipe II. The K_d1 and K_d2 values were 9.81 × 10^?4 mol L^?1 and 1.11 × 10^?7 (mol L^?1)² for 1:1 and 1:2 complexes of Pipe I with β‐CD, respectively. The K_d values obtained from fluorescence spectroscopy were in agreement with those from ESI‐MS titration. Copyright © 2010 John Wiley & Sons, Ltd.     

HPLC法拆分(-)-2(S)-苄基-4-酮-4-(顺式-全氢化异吲哚-2-基)丁酸钙对映体

目的：建立刺激胰岛素分泌的新型降糖药物(-)-2 (S)-苄基-4-酮-4-(顺式-全氢化异吲哚-2-基)丁酸钙对映体的HPLC拆分方法。方法：采用Sumichiral OA-3300手性柱(250 × 4.6 mm I.D., 5 μm), 柱温35℃,以0.05 mol·L-1醋酸铵的甲醇溶液为流动相,检测波长为210 nm。结果：本品两对映体在22分钟内实现良好分离,分离度达3以上,S－异构体分别在0.028 ~ 5.6 μg mL-1和0.03 ~ 6.0 μg mL-1范围内线性关系良好,回归方程分别为：Y=1.32×103x-2.54 (r=0.9997)和Y=1.15×103x-1.78 (r=0.9998),最低检测限分别为0.15 ng和0.10 ng,方法精密度RSD低于1.0% (n=5)。结论：建立的对映体分离方法可用于本品光学异构体的质量控制。     

Carbon Paste Electrode Incorporating 1‐[4‐(Ferrocenyl Ethynyl) Phenyl]‐1‐Ethanone for Electrocatalytic and Voltammetric Determination of Tryptophan

A carbon paste electrode spiked with 1‐[4‐ferrocenyl ethynyl) phenyl]‐1‐ethanone (4FEPE) was constructed by incorporation of 4FEPE in graphite powder‐paraffin oil matrix. It has been shown by direct current cyclic voltammetry and double step chronoamperometry that this electrode can catalyze the oxidation of tryptophan (Trp) in aqueous buffered solution. It has been found that under optimum condition (pH 7.00), the oxidation of Trp at the surface of such an electrode occurs at a potential about 200 mV less positive than at an unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient, α and rate constant for the chemical reaction between Trp and redox sites in 4FEPE modified carbon paste electrode (4FEPEMCPE) were also determined using electrochemical approaches. The electrocatalytic oxidation peak current of Trp showed a linear dependent on the Trp concentrations and linear calibration curves were obtained in the ranges of 6.00×10^?6 M–3.35×10^?3 M and 8.50×10^?7 M–6.34×10^?5 M of Trp concentration with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods, respectively. The detection limits (3σ) were determined as 1.80×10^?6 M and 5.60×10^?7 M by CV and DPV methods. This method was also examined as a selective, simple and precise new method for voltammetric determination of tryptophan in real sample.     

Electrochemical Sensor for Sensitive Determination of Ga(III) Ion Based on β‐Cyclodextrin Incorporated Multi‐walled Carbon Nanotubes and Imprinted Sol‐gel Composite Film

A novel sensor for detection of trace gallium ion [Ga(III)] was created by stepwise modification of a gold electrode with β‐cyclodextrin (β‐CD)/multi‐walled carbon nanotubes (MWCNTs) and an ion imprinted polymer (IIP). The sensor surface morphology was characterized by scanning electron microscopy. The electrochemical performance of the imprinted sensor was investigated by cyclic voltammetry, differential pulse voltammetry and chronoamperometry. The sensor displayed excellent selectivity towards the target Ga(III) ion. Meanwhile, the introduced MWCNTs displayed noticeable catalytic activity, and β‐CD demonstrated significant enrichment capacity. A linear calibration curve was obtained covering the concentration range from 5.0×10^?8 to 1.0×10^?4 mol·L^?1, with a detection limit of 7.6×10^?9 mol·L^?1. The proposed sensor was successfully applied to detect Ga(III) in real urine samples.     

Inclusion of Ethyl Acetoacetate Bearing 7‐Hydroxycoumarin Dye by β‐Cyclodextrin and its Cooperative Assembly with Mercury(II) Ions: Spectroscopic and Molecular Modeling Studies

The inclusion of the fluorescent organic dye, ethyl 3‐(7‐hydroxy‐2‐oxo‐2H‐chromen‐3‐yl)‐3‐oxopropanoate ( 1 ) by the host β‐cyclodextrin (β‐CD), and its response toward mercuric ions (Hg²⁺), was studied by UV/Vis, fluorescence, and ¹H NMR spectroscopic analyses, mass spectrometry and molecular modeling studies. ¹H NMR measurements together with molecular modeling studies for dye 1 demonstrate that it exhibits two tautomeric forms (keto and enol); however, when the dye is included into the β‐CD cavity, the enol form predominates. Moreover, by using spectroscopic and spectrometry techniques, a 1:1 stoichiometry was determined for the complexes formed between dye 1 (enol form) and β‐CD, with a binding constant (K_b1=1.8×10⁴ m ^?1) and for the dye 1 (keto form)‐Hg²⁺ (K_b2=2.3×10³ m ^?1). Interestingly, in the presence of 1 –β‐CD complex and mercuric ions, a ternary supramolecular system (Hg– 1 –β‐CD complex) was established, with a 1:1:1 stoichiometry and a K_b3 value of 4.3×10³ m ^?1, with the keto form of the dye being the only one present in this assembly. The three‐component system provides a starting point for the development of novel and directed supramolecular assemblies.     

Chiral Recognition of Penicillamine Enantiomers Based on DNA‐MWNT Complex Modified Electrode

Double‐stranded DNA and multiwalled carbon nanotube (MWNT) complex modified glassy carbon electrodes (DNA‐MWNT‐GCE) were employed to discriminate penicillamine (PA) enantiomers. Cyclic voltammetry, electrochemical impedance spectroscopy, atomic force microscopy and ultraviolet‐visible spectroscopy were used to characterize the enantioselective phenomenon. The results indicated that the binding effect between L ‐PA and DNA‐MWNTs was stronger than that of D ‐PA and DNA‐MWNTs. In addition, the influencing factors of the modified electrodes were systematically investigated. The modified electrodes exhibited a linear response towards PA enantiomers from 1.0×10^?1 to 1.0×10^?8 mol L^?1 and detection limits of 3.1×10^?9 and 3.3×10^?8 mol L^?1 for L ‐PA and D ‐PA, respectively.     

The study of enantioselectivity of all regioisomers of mono‐carboxymethyl‐β‐cyclodextrin used as chiral selectors in CE

This work documents the influence of the position of single carboxymethyl group on the β‐cyclodextrin skeleton on the enantioselectivity. These synthesized monosubstituted carboxymethyl cyclodextrin (CD) derivatives, native β‐cyclodextrin, and commercially available carboxymethyl‐β‐cyclodextrin with degree of substitution approximately 3 were used as additives into the BGE consisting of phosphate buffer at 20 mmol/L concentration, pH 2.5, and several biologically significant low‐molecular‐mass chiral compounds were enantioseparated by CE. The results indicate that different substituent location on β‐cyclodextrin skeleton has a significant influence on the enantioseparation of the investigated enantiomers. The enantioselectivity of 2^I‐O‐regioisomer was better than with native β‐cyclodextrin. Comparable results to native β‐cyclodextrin were obtained for 6^I‐O‐ regioisomer and the enantioselectivity of 3^I‐O‐regioisomer was even worse than with native β‐cyclodextrin. Commercially available derivative of CD provides better resolutions than the monosubstituted carboxymethyl CD derivatives for most of the investigated analytes.     

Fluorescence Dynamics of Monocyclodextrin– and Bis(thiol‐cyclodextrin)–Coumarin C153 Complexes

The solvation and confinement of coumarin C153 within supramolecular host/guest complexes based on β‐cyclodextrin (β‐CD) and 6‐deoxy‐6‐thio‐β‐cyclodextrin (β‐CD‐SH) in water are studied by fluorescence spectroscopy. For β‐CD/C153, the 1:1 complex is proposed, and for β‐CD‐SH/C153 both the 1:1 and 2:1 complexes are believed to be formed. The 2:1 β‐CD‐SH/C153 complex has an association constant of 4.2×10⁵ M ^?1 and a C153 population of 82 %, which are interestingly high values, indicating that the proposed β‐CD‐SH dimers structure are connected by covalent disulfide bonds; this is supported by mass spectrometry. Solvation related to fast hydrogen‐bond rearrangement as a part of fluorescence relaxation is determined by the ultrafast components of time‐resolved spectroscopy to be 3 and 7 ps for the 1:1 β‐CD/C153 and 2:1 β‐CD‐SH/C153 complexes, respectively.     

Axially Chiral TADF‐Active Enantiomers Designed for Efficient Blue Circularly Polarized Electroluminescence

The use of a chiral, emitting skeleton for axially chiral enantiomers showing activity in thermally activated delayed fluorescence (TADF) with circularly polarized electroluminescence (CPEL) is proposed. A pair of chiral stable enantiomers, (?)‐(S)‐Cz‐Ax‐CN and (+)‐(R)‐Cz‐Ax‐CN, was designed and synthesized. The enantiomers, both exhibiting intramolecular π‐conjugated charge transfer (CT) and spatial CT, show TADF activities with a small singlet–triplet energy difference (ΔE_ST) of 0.029 eV and mirror‐image circularly polarized luminescence (CPL) activities with large g_lum values. Notably, CP‐OLEDs based on the enantiomers feature blue electroluminescence centered at 468 nm with external quantum efficiencies (EQEs) of 12.5 and 12.7 %, and also show intense CPEL with g_EL values of ?1.2×10^?2 and +1.4×10^?2, respectively. These are the first CP‐OLEDs based on TADF‐active enantiomers with efficient blue CPEL.     

New single isomer negatively charged β‐cyclodextrin derivatives as chiral selectors in capillary electrophoresis

To improve resolution power of chiral selector and enantiomeric peak efficiency in CE, single isomer negatively charged β‐CD derivatives, mono(6‐deoxy‐6‐sulfoethylthio)‐β‐CD (SET‐β‐CD) bearing one negative charge and mono[6‐deoxy‐6‐(6‐sulfooxy‐5,5‐bis‐sulfooxymethyl)hexylthio]‐β‐CD (SMHT‐β‐CD) carrying three negative charges, were synthesized. The structure of these two β‐CD derivatives was confirmed by ¹H NMR and MS. SET‐β‐CD and SMHT‐β‐CD successfully resolved the enantiomers of several basic model compounds. SMHT‐β‐CD provided for a significantly greater enantioseparation than SET‐β‐CD at lower concentrations. This appears to be due to the higher binding affinity of SMHT‐β‐CD to the model compounds and the wider separation window resulting from an increased countercurrent mobility of the selector. Overall, the new chiral selectors provided enantioseparations with high peak efficiency while avoiding peak distortion due to polydispersive and electrodispersive effects. The information obtained from an apparent binding constant study suggested that the enantioseparation of the model compounds followed the predictions of charged resolving agent migration model and that the observed degree of enantioseparation difference were due to the magnitude of differences in both enantiomer‐chiral selector binding affinities (ΔK) and the mobilities of the complexed enantiomers (Δμ_c).     

Rate constants of the gas‐phase reactions of OH radicals with trans‐2‐hexenal,trans‐2‐octenal,and trans‐2‐nonenal

The rate constants of the gas‐phase reaction of OH radicals with trans‐2‐hexenal, trans‐2‐octenal, and trans‐2‐nonenal were determined at 298 ± 2 K and atmospheric pressure using the relative rate technique. Two reference compounds were selected for each rate constant determination. The relative rates of OH + trans‐2‐hexenal versus OH + 2‐methyl‐2‐butene and β‐pinene were 0.452 ± 0.054 and 0.530 ± 0.036, respectively. These results yielded an average rate constant for OH + trans‐2‐hexenal of (39.3 ± 1.7) × 10^?12 cm³ molecule^?1 s^?1. The relative rates of OH+trans‐2‐octenal versus the OH reaction with butanal and β‐pinene were 1.65 ± 0.08 and 0.527 ± 0.032, yielding an average rate constant for OH + trans‐2‐octenal of (40.5 ± 2.5) × 10^?12 cm³ molecule^?1 s^?1. The relative rates of OH+trans‐2‐nonenal versus OH+ butanal and OH + trans‐2‐hexenal were 1.77 ± 0.08 and 1.09 ± 0.06, resulting in an average rate constant for OH + trans‐2‐nonenal of (43.5 ± 3.0) × 10^?12 cm³ molecule^?1 s^?1. In all cases, the errors represent 2σ (95% confidential level) and the calculated rate constants do not include the error associated with the rate constant of the OH reaction with the reference compounds. The rate constants for the hydroxyl radical reactions of a series of trans‐2‐aldehydes were compared with the values estimated using the structure activity relationship. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 483–489, 2009     

High‐performance liquid chromatographic enantioseparation of isoxazoline‐fused 2‐aminocyclopentanecarboxylic acids on a chiral ligand‐exchange stationary phase

The application of a chiral ligand‐exchange column for the direct high‐performance liquid chromatographic enantioseparation of unusual β‐amino acids with a sodium N‐((R)‐2‐hydroxy‐1‐phenylethyl)‐N‐undecylaminoacetate‐Cu(II) complex as chiral selector is reported. The investigated amino acids were isoxazoline‐fused 2‐aminocyclopentanecarboxylic acid analogs. The chromatographic conditions were varied to achieve optimal separation. The effects of temperature were studied at constant mobile phase compositions in the temperature range 5–45°C, and thermodynamic parameters were calculated from plots of lnk or lnα versus 1/T. Δ(ΔH°) ranged from –2.3 to 2.2 kJ/mol, Δ(ΔS°) from –3.0 to 7.8 J mol^?1 K^?1 and –Δ(ΔG°) from 0.1 to 1.7 kJ/mol, and both enthalpy‐ and entropy‐controlled enantioseparations were observed. The latter was advantageous with regard to the shorter retention and greater selectivity at high temperature. Some mechanistic aspects of the chiral recognition process are discussed with respect to the structures of the analytes. The sequence of elution of the enantiomers was determined in all cases.     

Distribution of the methyl radical adduct of N‐benzylidene‐1‐diethoxyphosphoryl‐1‐methylethylamine N‐oxide‐type nitrones in water–sodium dodecyl sulfate micelles: an electron paramagnetic resonance spin trapping study

The behavior of the methyl radical adduct of six β‐phosphorylated nitrones in the N‐benzylidene‐1‐diethoxyphosphoryl‐1‐methylethylamine N‐oxide series in the presence of sodium dodecyl sulfate (SDS) micelles was followed by electron paramagnetic resonance spectroscopy. Except when the highly hydrophilic trap 4‐PyOPN (2) was used, all the adducts were found to partition significantly between micelles and the bulk aqueous phase. The average correlation time τ of the exchange of spin adducts between SDS micelles and water was found to be in the range 5 × 10^?8—4 × 10^?7 s, which is in the region of the life time of an SDS monomer in the micelle structure. In each case, the adduct affinity for the micelles has been quantified by evaluating its micelle–water distribution coefficient K_d. Copyright © 2002 John Wiley & Sons, Ltd.     

Chiral sensing of Eu(III)‐containing achiral polymer complex from chiral amino acids coordination induction

The β‐diketonate‐based achiral polymer P‐1 could be synthesized by the polymerization of 3,7‐dibromo‐2,8‐dimethoxy‐5,5‐dioctyl‐5H‐dibenzo[b,d]silole ( M1 ) with (Z)?1,3‐bis(4‐ethynylphenyl)?3‐hydroxyprop‐en‐1‐one ( M2 ) via typical Sonogashira coupling reaction. The β‐diketonate unit in the main chain backbone of P‐1 can further coordinate with Eu(TTA)_x [TTA^? = 4,4,4‐trifluoro‐1‐(thiophen‐2‐yl)butane‐1,3‐dionate anion, X = 1, 2, 3] to afford corresponding Eu(III)‐containing polymer complexes. The resulting achiral polymer complex P‐2 (X = 2) can exhibit strong circular dichroism (CD) response toward both N‐Boc‐l and d‐ proline enantiomers. The CD signal was preliminarily attributed to coordination induction between chiral N‐Boc‐proline and the Eu(III) complex moiety. The linear regression analysis of CD sensing shows a good agreement between the magnitude of molar ellipticity and concentration of chiral N‐Boc‐l or d‐ proline, which indicates this kind Eu(III)‐containing achiral polymer complex can be used as a chiral probe for enantioselective recognition of N‐Boc‐l or d‐ proline enantiomers based on Cotton effect of CD spectra. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3080–3086