- NMR Structure Determination of Ion Pairs Derived from Quinine: A Model for Templating in Asymmetric Phase-Transfer Reductions by BH4- with Implications for Rational Design of Phase-Transfer Catalysts
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The solution structures of ion pairs formed by quarternary ammonium ions derived from quinine alkaloid with small hard anions (BH-4 or Cl-) in CDCl3 have been characterized by nuclear magnetic resonance methods. Structural observations have been correlated with the sense of asymmetric induction observed in the phase-transfer reduction of 9-anthryl trifluoromethyl ketone by borohydride (BH-4) when catalyzed by the quaternary N-benzylquinine ammonium ion. From interionic nuclear Overhauser effects (NOEs), it appears that the BH-4 ion occupies two of the four trigonal pyramidal sites formed by substituents of the quarternary nitrogen of the catalyst cation. One of these sites is in close proximity to the cation's hydroxyl group that is strictly required for asymmetric induction in the model reaction, while the other site is near the vinyl group on the cation. The vinyl group does not appear to be important for determining the sense or extent of asymmetric induction. Using energy-minimized structures derived from NMR data, it was predicted that the N-(9-methyleneanthryl)quinine - quarternary ammonium catalyst would give improved asymmetric induction in the model reaction due to a preferred anion occupancy at the site near the hydroxyl group. An improvement in enantiomeric excess (ee) is observed using the anthryl-modified catalyst, and NMR studies on the modified catalyst confirm the predicted change in anion binding site occupancies. The changes in site occupancies determined by NMR can be fitted to a simple kinetic model that correctly predicts the extent of change in ee.
- Hofstetter, Christine,Wilkinson, Patricia Stone,Pochapsky, Thomas C.
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- Preparative Resolution of Racemates on a Chiral Liquid Chromatography Column
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A 2 in. x 30 in. liquid chromatography column packed with a chiral stationary phase derived from (R)-phenylglycine has been found capable of resolving gram or larger samples of a variety of racemates.Nine such resolutions are presented.The racemates resol
- Pirkle, William H.,Finn, John M.
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- Ultrasound-Controlled Chiral Separation of Four Amino Acids and 2,2,2-Trifluoro-1-(9-anthryl)ethanol
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Chiral separation of 4-hydroxyphenylglycine, phenylglycine, tryptophan, methionine, and 2,2,2-trifluoro-1-(9-anthryl)ethanol (TFAE) was performed under ultrasound reduction at room temperature and high temperature (50 °C). At high temperature (50 °C), both α and Rs were improved slightly under ultrasound reduction as compared to those under non-ultrasonic and ultrasonic irradiation (50 watt/L) conditions. Even at low temperatures, the largest α was observed under ultrasound reduction conditions, except in the case of methionine. However, at low temperature, Rs was reduced under ultrasound (50 watt/L) irradiation, but was improved under ultrasound reduction rather than under the continuous ultrasonic irradiation. Similar to the fact that gradient elution (based on solvent polarity) can improve α, ultrasound reduction can improve α and Rs. Ultrasound reduction is demonstrated to aid the rapid separation of chiral compounds with improved resolution, especially, at high temperatures. Although chromatographic separation using ultrasound has been rarely dealt with until now, ultrasound can be used as an external field in chromatography.
- Lee, Jae Hwan,Ryoo, Jae Jeong
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p. 146 - 149
(2019/02/07)
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- Three-State Switchable Chiral Stationary Phase Based on Helicity Control of an Optically Active Poly(phenylacetylene) Derivative by Using Metal Cations in the Solid State
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An unprecedented three-state switchable chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC) was developed using a helical poly(phenylacetylene) bearing a chiral (R)-α-methoxyphenylacetic acid residue as the pendant (poly-1). The left- and right-handed helical conformations were induced in poly-1-based CSP upon coordination with a catalytic amount of soluble sodium and cesium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate salts (MBArF), respectively, which are soluble in the HPLC conditions [hexane-2-propanol (95:5, v/v)]. The switch between the two different helical states of poly-1 can be easily achieved by rinsing the poly-1-based CSP with MeOH and the subsequent addition of the proper MBArF salt. Using this dynamic helical CSP, we demonstrate how changes on the orientation of the secondary structure of a chiral polymer (right-handed, left-handed, and racemic helices) can alter and even invert the elution order of the enantiomers. This study was done without adding chiral additives or changing the mobile phase, which could produce changes on the retention times and make it more difficult to determine the role of the secondary structure during the chiral recognition process.
- Hirose, Daisuke,Isobe, Asahi,Qui?oá, Emilio,Freire, Félix,Maeda, Katsuhiro
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supporting information
(2019/06/10)
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- Three-State Switchable Chiral Stationary Phase Based on Helicity Control of an Optically Active Poly(phenylacetylene) Derivative by Using Metal Cations in the Solid State
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An unprecedented three-state switchable chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC) was developed using a helical poly(phenylacetylene) bearing a chiral (R)-α-methoxyphenylacetic acid residue as the pendant (poly-1). The left- and right-handed helical conformations were induced in poly-1-based CSP upon coordination with a catalytic amount of soluble sodium and cesium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate salts (MBArF), respectively, which are soluble in the HPLC conditions [hexane-2-propanol (95:5, v/v)]. The switch between the two different helical states of poly-1 can be easily achieved by rinsing the poly-1-based CSP with MeOH and the subsequent addition of the proper MBArF salt. Using this dynamic helical CSP, we demonstrate how changes on the orientation of the secondary structure of a chiral polymer (right-handed, left-handed, and racemic helices) can alter and even invert the elution order of the enantiomers. This study was done without adding chiral additives or changing the mobile phase, which could produce changes on the retention times and make it more difficult to determine the role of the secondary structure during the chiral recognition process.
- Hirose, Daisuke,Isobe, Asahi,Qui?oá, Emilio,Freire, Félix,Maeda, Katsuhiro
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supporting information
p. 8592 - 8598
(2019/06/13)
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- Synthesis of new C3 symmetric amino acid- and aminoalcohol-containing chiral stationary phases and application to HPLC enantioseparations
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We recently reported a new C3-symmetric (R)-phenylglycinol N-1,3,5-benzenetricarboxylic acid-derived chiral high-performance liquid chromatography (HPLC) stationary phase (CSP 1) that demonstrated better results as compared to a previously described N-3,5-dintrobenzoyl (DNB) (R)-phenylglycinol-derived CSP. Over a decade ago, (S)-leucinol, (R)-phenylglycine, and (S)-leucine derivatives were used as the starting materials of 3,5-DNB-based Pirkle-type CSPs for chiral separation. In this study, three new C3-symmetric CSPs (CSP 2, 3, and 4) were prepared by combining the ideas and results mentioned above. Here we describe the synthetic procedures and applications of the new C3-symmetric CSPs (CSP 2–CSP 4).
- Yu, Jeongjae,Armstrong, Daniel W.,Ryoo, Jae Jeong
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- Ultrafast chiral separations for high throughput enantiopurity analysis
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Recent developments in fast chromatographic enantioseparations now make high throughput analysis of enantiopurity on the order of a few seconds achievable. Nevertheless, routine chromatographic determinations of enantiopurity to support stereochemical investigations in pharmaceutical research and development, synthetic chemistry and bioanalysis are still typically performed on the 5-20 min timescale, with many practitioners believing that sub-minute enantioseparations are not representative of the molecules encountered in day to day research. In this study we develop ultrafast chromatographic enantioseparations for a variety of pharmaceutically-related drugs and intermediates, showing that sub-minute resolutions are now possible in the vast majority of cases by both supercritical fluid chromatography (SFC) and reversed phase liquid chromatography (RP-LC). Examples are provided illustrating how such methods can be routinely developed and used for ultrafast high throughput analysis to support enantioselective synthesis investigations.
- Barhate, Chandan L.,Joyce, Leo A.,Makarov, Alexey A.,Zawatzky, Kerstin,Bernardoni, Frank,Schafer, Wes A.,Armstrong, Daniel W.,Welch, Christopher J.,Regalado, Erik L.
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supporting information
p. 509 - 512
(2017/01/13)
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- New chiral stationary phases based on xanthone derivatives for liquid chromatography
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Six chiral derivatives of xanthones (CDXs) were covalently bonded to silica, yielding the corresponding xanthonic chiral stationary phases (XCSPs). The new XCSPs were packed into stainless-steel columns with 150 x 4.6 mm i.d. Moreover, the greening of the chromatographic analysis by reducing the internal diameter (150 x 2.1 mm i.d.) of the liquid chromatography (LC) columns was also investigated. The enantioselective capability of these phases was evaluated by LC using different chemical classes of chiral compounds, including several types of drugs. A library of CDXs was evaluated in order to explore the principle of reciprocity as well as the chiral self-recognition phenomenon. The separation of enantiomeric mixtures of CDXs was investigated under multimodal elution conditions. The XCSPs provided high specificity for the enantiomeric mixtures of CDXs evaluated mainly under normal-phase elution conditions. Furthermore, two XCSPs were prepared with both enantiomers of the same xanthonic selector in order to confirm the inversion order elution.
- Fernandes, Carla,Tiritan, Maria Elizabeth,Cravo, Sara,Phyo, Ye’ Zaw,Kijjoa, Anake,Silva, Artur M.S.,Cass, Quezia B.,Pinto, Madalena M.M.
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p. 430 - 442
(2017/07/25)
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- Preparation and evaluation of regioselectively substituted amylose derivatives for chiral separations
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Six novel regioselectively substituted amylose derivatives with a benzoate at 2-position and two different phenylcarbamates at 3- and 6-positions were synthesized and their structures were characterized by 1H nuclear magnetic resonance (NMR) spectroscopy. Their enantioseparation abilities were then examined as chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) after they were coated on 3-aminopropyl silica gels. Investigations indicated that the substituents at the 3- and 6-positions played an important role in chiral recognition of these amylose 2-benzoate serial derivatives. The derivatives demonstrated characteristic enantioseparation and some racemates were better resolved on these derivatives than on Chiralpak AD, which is one of the most efficient CSPs, utilizing coated amylose tris(3,5-dimethylphenylcarbamate) as the chiral selector. Among the derivatives prepared, amylose 2-benzoate-3-(phenylcarbamate/4-methylphenylcarbamate)-6-(3,5-dimethylphenylcarbamate) exhibited chiral recognition abilities comparable to that of Chiralpak AD and may be useful CSPs in the future. The effect of mobile phase on chiral recognition was also studied. In general, with the decreased concentration of 2-propanol, better resolutions were obtained with longer retention times. Moreover, when ethanol was used instead of 2-propanol, poorer resolutions were often achieved. However, in some cases, improved enantioselectivity was achieved with ethanol rather than 2-propanol as the mobile phase modifier.
- Tang, Shouwan,Jin, Zhaolei,Sun, Baishen,Wang, Fang,Tang, Wenyuan
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p. 512 - 521
(2017/08/26)
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- A 3D Homochiral MOF [Cd2(d-cam)3]?2Hdma?4dma for HPLC Chromatographic Enantioseparation
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Up to now, some chiral metal-organic frameworks (MOFs) have been reported for enantioseparation in liquid chromatography. Here we report a homochiral MOF, [Cd2(d-cam)3]·2Hdma·4dma, used as a new chiral stationary phase for high-performance liquid chromatographic enantioseparation. Nine racemates of alcohol, naphthol, ketone, and base compounds were used as analytes for evaluating the separation properties of the chiral MOF packed column. Moreover, some effects such as mobile phase composition, column temperature, and analytes mass for separations on this chiral column also were investigated. The relative standard deviations for the resolution values of run-to-run and column-to-column were less than 2.1% and 3.2%, respectively. The experimental results indicate that the homochiral MOF offered good recognition ability, which promotes the application of chiral MOFs use as stationary phase for enantioseparation. Chirality 28:340-346, 2016.
- Zhang, Mei,Chen, Xinglian,Zhang, Junhui,Kong, Jiao,Yuan, Liming
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p. 340 - 346
(2016/03/19)
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- Synthesis of optically active poly(diphenylacetylene)s using polymer reactions and an evaluation of their chiral recognition abilities as chiral stationary phases for HPLC
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A series of optically active poly(diphenylacetylene) derivatives bearing a chiral substituent (poly-2S) or chiral and achiral substituents (poly-(2Sx-co-31-x)) on all of their pendant phenyl rings were synthesized by the reaction of poly(bis(4-carboxyphenyl)acetylene) with (S)-1-phenylethylamine ((S)-2) or benzylamine (3) in the presence of a condensing reagent. Their chiroptical properties and chiral recognition abilities as chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) were investigated. Poly-2S and poly-(2Sx-co-31-x) (0.06 x-co-31-x)). Furthermore, h-poly-2S and h-poly-(2S0.36-co-30.64) emitted circularly polarized luminescence with opposite signs. h-Poly-2S showed higher chiral recognition abilities toward a larger number of racemates than poly-2S without a preferred-handed helicity and the previously reported preferred-handed poly(diphenylacetylene) derivative bearing the same chiral substituent on half of its pendant phenyl rings. h-Poly-(2S0.36-co-30.64) also exhibited good chiral recognition abilities toward several racemates, though the elution order of some enantiomers was reversed compared with h-poly-2S.
- Maeda, Katsuhiro,Maruta, Miyuki,Sakai, Yuki,Ikai, Tomoyuki,Kanoh, Shigeyoshi
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- Photochemically immobilized 4-methylbenzoyl cellulose as a powerful chiral stationary phase for enantioselective chromatography
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A process to immobilize para-methylbenzoyl cellulose (PMBC) on silica gel has been developed and applied to prepare chiral stationary phases (CSPs) for enantioselective chromatography. The immobilization was achieved by simple irradiation of the polysaccharide derivative with ultraviolet light after coating on a silica gel support. The influence of parameters such as irradiation time and solvent on immobilization effectiveness were investigated. The performance of the prepared immobilized phases were evaluated by injection of a series of racemic compounds onto the packed columns and determination of their chiral recognition ability. By contrast to the classical coated phase, the immobilized CSP can be used under various chromatographic conditions without limitation of organic solvent types as the mobile phase. This extended applicability permits to improve selectivity and to resolve chiral compounds which are not or only poorly soluble in the mobile phases which are compatible with the non-immobilized PMBC stationary phase.
- Francotte, Eric,Huynh, Dan,Zhang, Tong
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- Temperature-triggered switchable helix-helix inversion of poly(phenylacetylene) bearing L-valine ethyl ester pendants and its chiral recognition ability
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A phenylacetylene containing the L-valine ethyl ester pendant (PAA-Val) was synthesized and polymerized by an organorhodium catalyst (Rh(nbd)BPh4) to produce the corresponding one-handed helical cis-poly(phenylacetylene) (PPAA-Val). PPAA-Val showed a unique temperature-triggered switchable helix-sense in chloroform, while it was not observed in highly polar solvents, such as N,N′-dimethylformamide (DMF). By heating the solution of PPAA-Val in chloroform, the sign of the CD absorption became reversed, but recovered after cooling the solution to room temperature. Even after six cycles of the heating-cooling treatment, the helix sense of the PPAA-Val's backbone was still switchable without loss of the CD intensity. The PPAA-Val was then coated on silica gel particles to produce novel chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC). These novel PPAA-Val based CSPs showed a high chiral recognition ability for racemic mandelonitrile (α = 2.18) and racemic trans-N,N′-diphenylcyclohexane-1,2-dicarboxamide (α = 2.60). Additionally, the one-handed helical cis-polyene backbone of PPAA-Val was irreversibly destroyed to afford PPAA-Val-H by heating in dimethyl sulfoxide (DMSO) accompanied by the complete disappearance of the Cotton effect. Although PPAA-Val-H had the same L-valine ethyl ester pendants as its cis-isomer PPAA-Val, it showed no chiral recognition. It was concluded that the one-handed helical cis-polyene backbone of PPAA-Val plays an important role in the chiral recognition ability.
- Zhou, Yanli,Zhang, Chunhong,Qiu, Yuan,Liu, Lijia,Yang, Taotao,Dong, Hongxing,Satoh, Toshifumi,Okamoto, Yoshio
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- Synthesis and Enantioseparation Ability of Xylan Bisphenylcarbamate Derivatives as Chiral Stationary Phases in HPLC
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Ten novel xylan bisphenylcarbamate derivatives bearing meta- and para-substituents on their phenyl groups were synthesized and their chiral recognition abilities were evaluated as the chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) after coating them on macroporous silica. The chiral recognition abilities of these CSPs depended on the nature, position, and number of the substituents on the phenyl moieties. The introduction of an electron-donating group was more attractive than an electron-withdrawing group to improve the chiral recognition ability of the xylan phenylcarbamate derivatives. Among the CSPs discussed in this study, xylan bis(3,5-dimethylphenylcarbamate)-based CSP seems to possess the highest resolving power for many racemates, and the meta-substituted CSPs showed relatively better chiral recognition than the para-substituted ones. For some racemates, the xylan bis(3,5-dimethylphenylcarbamate) derivative exhibited higher enantioselectivity than the CSP based on cellulose tris(3,5-dimethylphenylcarbamate). Chirality 27:518-522, 2015
- Li, Geng,Shen, Jun,Li, Qiang,Okamoto, Yoshio
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p. 518 - 522
(2015/08/03)
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- Enantioseparation on Riboflavin Derivatives Chemically Bonded to Silica Gel as Chiral Stationary Phases for HPLC
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Acetylated and/or 3,5-dimethylphenylcarbamated riboflavins were prepared and the resulting riboflavin derivatives as well as natural riboflavin were regioselectively immobilized on silica gel through chemical bonding at the 5'-O- or 3-N-position of the riboflavin to develop novel chiral stationary phases (CSPs) for enantioseparation by high-performance liquid chromatography (HPLC). The chiral recognition abilities of the obtained CSPs were significantly dependent on the structures of the riboflavin derivatives, the position of the chemical bonding on the silica gel, and the structures of the racemic compounds. The CSPs bonded at the 5'-O-position on the silica gel tended to well separate helicene derivatives, while the CSPs bonded at the 3-N-position composed of acetylated and 3,5-dimethylphenylcarbamated riboflavins showed a better resolving ability toward helicene derivatives and bulky aromatic racemic alcohols, respectively, and some of them were completely separated into the enantiomers. The observed difference in the chiral recognition abilities of these riboflavin-based CSPs is discussed based on the difference in their structures, including the substituents of riboflavin and the positions immobilized on the silica gel. Chirality 27:507-517, 2015.
- Kumano, Daisuke,Iwahana, Soichiro,Iida, Hiroki,Shen, Chengshuo,Crassous, Jeanne,Yashima, Eiji
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p. 507 - 517
(2015/08/03)
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- Influence of Helical Structure on Chiral Recognition of Poly(phenylacetylene)s Bearing Phenylcarbamate Residues of L -Phenylglycinol and Amide Linage as Pendants
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Four poly(phenylacetylene)s (PPA-1, PPA-2, PPA-3, PPA-4) bearing phenylcarbamate residues of L-phenylglycinol and amide linkage as pendants were prepared to be used as chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC), and the influences of coating solvents, dimethylformamide (DMF) and tetrahydrofuran (THF), which were used for coating the polymers on silica gel, on the helical structure of the polymers and their chiral recognition abilities were investigated. The structure analysis of PPA-1, PPA-2, PPA-3, PPA-4 by 1H nuclear magnetic resonance (NMR), size exclusion chromatography (SEC), optical rotation, and circular dichroism (CD) spectra indicated that the polymers possess the cis-transoidal structure with dynamic helical conformation. The polymers in THF seem to have shorter conjugated helical main chains along with a tighter twist conformation than those in DMF. The chiral recognition abilities of PPA-1, PPA-2, PPA-3, PPA-4 with the different helical structures induced by the coating solvents were evaluated as the CSPs in HPLC. The helical structures of PPA-1, PPA-2, PPA-3, PPA-4 induced with THF are preferable for chiral recognition for some racemates compared to those induced with DMF, and higher chiral recognition abilities of PPA-1, PPA-2, PPA-3, PPA-4 were achieved using THF.
- Zhang, Chunhong,Ma, Rui,Wang, Hailun,Sakai, Ryosuke,Satoh, Toshifumi,Kakuchi, Toyoji,Liu, Lijia,Okamoto, Yoshio
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p. 500 - 506
(2015/08/03)
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- Macromolecular helicity induction and memory in a poly(biphenylylacetylene) bearing an ester group and its application to a chiral stationary phase for high-performance liquid chromatography
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An optically inactive poly(biphenylylacetylene) bearing an ester group at the 4′-position of the pendants formed a preferred-handed helical conformation and biased axial chirality in the pendants through a noncovalent interaction with a chiral alcohol, both of which were retained (memorized) even after removal of the chiral alcohol. The chiral stationary phase for high-performance liquid chromatography, prepared by coating the polymer with macromolecular helicity memory on silica gel, showed good chiral recognition ability towards various racemates.
- Ishidate, Ryoma,Shimomura, Kouhei,Ikai, Tomoyuki,Kanoh, Shigeyoshi,Maeda, Katsuhiro
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p. 946 - 948
(2015/08/24)
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- Synthesis and chiral recognition ability of a novel fullerene-functionalized cellulose derivative
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The fullerene-functionalized cellulose derivative 1 was synthesized and coated onto silica gel as chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC). The chiral recognition ability of the obtained chiral packing material (CPM) was evaluated by HPLC with ten types of racemates 2-11. This CPM could be used in the eluents including chloroform and terahydrofuran (THF), which are usually unsuitable solvents for conventional coating-type CPMs. Hence the scope of application of this CPM is wider than conventional coating CPM.
- Gao, Bo,Xu, Zeyu,Fan, Luan,Xu, Xiaodong,Bai, Jianwei,Shen, Xiande
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p. 1479 - 1481
(2015/11/24)
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- Synthesis and chiral recognition of helical poly(phenylacetylene)s bearing L-phenylglycinol and its phenylcarbamates as pendants
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A series of novel stereoregular one-handed helical poly(phenylacetylene) derivatives (PPA-1 and PPA-1a-g) bearing L-phenylglycinol and its phenylcarbamate residues as pendants was synthesized for use as chiral stationary phases (CSPs) for HPLC, and their chiral recognition abilities were evaluated using 13 racemates. The phenylcarbamate residues include an unsubstituted phenyl, three chloro-substituted phenyls (3-Cl, 4-Cl, 3,5-Cl2), and three methyl-substituted phenyls (3-CH3, 4-CH3, 3,5-(CH3)2). The acidity of the phenylcarbamate N-H proton and the hydrogen bonds formed between the N-H groups of the phenylcarbamate residues were dependent on the type, position, and the number of substituents on the phenylcarbamate residues. The chiral recognition abilities of these polymers significantly depended on the dynamic helical conformation of the main chain with more or less regularly arranged pendants. The chiral recognition abilities seem to be improved by the introduction of substituents on the phenylcarbamate residues, and PPA-1d bearing the more acidic N-H groups due to the 3,5-dichloro substituents, exhibited a higher chiral recognition than the others. PPA-1d showed an efficient chiral recognition for some racemates, and baseline separation was possible for racemates 5, 11, 12, and 15.
- Zhang, Chunhong,Wang, Hailun,Yang, Taotao,Ma, Rui,Liu, Lijia,Sakai, Ryosuke,Satoh, Toshifumi,Kakuchi, Toyoji,Okamoto, Yoshio
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p. 809 - 821
(2015/03/04)
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- Synthesis and chiral recognition of nickel(II) macrocyclic complex with (R)-naphthylethyleneamine pendant groups and its self-assembled framework
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A novel nickel(II) hexaaza macrocyclic complex, [Ni(LR,R)] (ClO4)2 (), containing chiral pendant groups was synthesized by an efficient one-pot template condensation and characterized (LR,R1,8-di((R)-α-methylnaphthyl)-1,3,6,8,10,13- hexaazacyclotetradecane). The crystal structure of compound was determined by single-crystal X-ray analysis. The complex was found to have a square-planar coordination environment for the nickel(II) ion. Open framework [Ni(L R,R)]3[C6H3(COO)3] 2 () was constructed from the self-assembly of compound with deprotonated 1,3,5-benzenetricarboxylic acid, BTC3-. Chiral discrimination of rac-1,1'-bi-2-naphthol and rac-2,2,2-trifluoro-1-(9-anthryl) ethanol was performed to determine the chiral recognition ability of the chiral complex () and its self-assembled framework (). Binaphthol showed a good chiral discrimination on the framework (). The optimum experimental conditions for the chiral discrimination were examined by changing the weight ratio between the macrocyclic complex or self-assembled framework and racemates. The detailed synthetic procedures, spectroscopic data including single-crystal X-ray analysis, and the results of the chiral recognition for the compounds are described. Copyright
- Min, Kil Sik,Park, Mi Jung,Ryoo, Jae Jeong
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- Preparation of bonded cellulose tris(3,5-dimethylphenylcarbamate) chiral stationary phases by using three bifunctional reagents
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Three di-acyl chlolide reagents, adipoyl chloride, terephthaloyl chloride and isophthaloyl chloride, were used as spacer reagents to prepare bonded type of three cellulose (3,5-dimethylphenyl)carbamate (CDMPC) chiral stationary phases (CSPs). The CDMPC CSPs were prepared using these three acid chlorides as spacer agents at the 6-position of the primary hydroxyl group on the glucose unit of cellulose regioselectively. The chiral recognition ability of the prepared CSPs for five racemates was evaluated by normal-phase high-performance liquid chromatography (HPLC) with the following mobile phases: hexane/isopropanol (IPA), hexane/IPA/ tetrahydrofuran (THF) and hexane/IPA/chloroform. The result showed that these prepared CSPs can be used in THF and chloroform solutions and the chiral recognition abilities of the CSPs were improved depending on the eluents and chiral samples.
- Zhang, Yi Jun,Huang, Mingxian,Zhang, Yuping,Ryoo, Jae Jeong
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p. 2623 - 2628
(2013/10/22)
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- Influence of stereoregularity and linkage groups on chiral recognition of poly(phenylacetylene) derivatives bearing L -leucine ethyl ester pendants as chiral stationary phases for HPLC
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Stereoregular poly(phenylacetylene) derivatives bearing L-leucine ethyl ester pendants, poly-1 and poly-2a, were, respectively, synthesized by the polymerization of N-(4-ethynylphenylcarbamoyl)-L-leucine ethyl ester (1) and N-(4-ethynylphenyl-carbonyl)-L-leucine ethyl ester (2) using Rh(nbd)BPh 4 as a catalyst, while stereoirregular poly-2b was synthesized by solid-state thermal polymerization of 2. Their chiral recognition abilities for nine racemates were evaluated as chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) after coating them on silica gel. Both poly-1 and poly-2a with a helical conformation showed their characteristic recognition depending on coating solvents and the linkage groups between poly(phenylacetylene) and L-leucine ethyl ester pendants. Poly-2a with a shorter amide linkage showed higher chiral recognition than poly-1 with a longer urea linkage. Coating solvents played an important role in the chiral recognition of both poly-1 and poly-2a due to the different conformation of the polymer main chains induced by the solvents. A few racemates were effectively resolved on the poly-2a coated with a MeOH/CHCl3 (3/7, v/v) mixture. The separation factors for these racemates were comparable to those obtained on the very popular CSPs derived from polysaccharide phenylcarbamates. Stereoirregular poly-2b exhibited much lower chiral recognition than the corresponding stereoregular, helical poly-2a, suggesting that the regular structure of poly(phenylacetylene) main chains is essential to attain high chiral recognition.
- Zhang, Chunhong,Liu, Fangbin,Li, Yufa,Shen, Xiande,Xu, Xiaodong,Sakai, Ryosuke,Satoh, Toshifumi,Kakuchi, Toyoji,Okamoto, Yoshio
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p. 2271 - 2278
(2013/05/09)
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- Cinchona alkaloid/TMAF combination: Enantioselective trifluoromethylation of aryl aldehydes
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The catalytic enantioselective trifluoromethylation reaction of aromatic aldehydes using the Ruppert-Prakash reagent (Me3SiCF3) has been disclosed, with an operationally simple procedure, based on the combination of sterically demand
- Kawai, Hiroyuki,Mizuta, Satoshi,Tokunaga, Etsuko,Shibata, Norio
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- Solution-phase synthesis and evaluation of tetraproline chiral stationary phases
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A protocol was developed for the solution-phase synthesis of multigram amounts of two 9-fluorenylmethoxycarbonyl (Fmoc)-protected tetraproline peptides. These tetraproline peptides were then attached to amino derivatized silica gel. The replacement of the Fmoc group with the trimethylacetyl group lead to two tetraproline chiral stationary phases (CSPs). A comparison of the chromatographic behavior of these two solution-phase-synthesized tetraproline CSPs with that prepared by stepwise solid-phase synthesis revealed that all three had similar chromatographic performance for resolving 53 model analytes. This suggests that the solution-phase synthesis of oligoprolines, which allows for the specific benefits of good batch reproducibility, selector homogeneity, and possibly low cost, is a feasible alternative to the solid-phase synthesis of oligoproline CSPs. Copyright
- Dai, Zhi,Ye, Guozhong,Pittman Jr., Charles U.,Li, Tingyu
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experimental part
p. 329 - 338
(2012/05/20)
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- Enantioseparation of typical pesticides using cellulose carbamate stationary phases by capillary liquid chromatography
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Cellulose-tris(3,5-dimethylphenylcarbamate) was initially synthesized as the chiral selector, then stable coated and bonded chiral stationary phases were prepared, respectively, using aminopropyl-functionalized silica gel as the support media. The prepared stationary phases were used for micro-column chiral separation by self-installed capillary high performance liquid chromatography system. Eighteen kind of chiral compounds including some typical pesticides were tested on both prepared chiral stationary phases and different chromatographic parameters such as resolution and retention time were comparatively investigated.
- Bai, Lian-Yang,Zhang, Yu-Ping,Deng, Pu-Hong,Zhang, Yi-Jun,Chen, Jun
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experimental part
p. 4917 - 4922
(2012/10/08)
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- Kinetic resolution of secondary alcohols using amidine-based catalysts
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Kinetic resolution of racemic alcohols has been traditionally achieved via enzymatic enantioselective esterification and ester hydrolysis. However, there has long been considerable interest in devising nonenzymatic alternative methods for this transformation. Amidine-based catalysts (ABCs), a new class of enantioselective acyl transfer catalysts developed in our group, have demonstrated, inter alia, high efficacy in the kinetic resolution of benzylic, allylic, and propargylic secondary alcohols and 2-substituted cycloalkanols, and thus provide a viable alternative to enzymes.
- Li, Ximin,Jiang, Hui,Uffman, Eric W.,Guo, Lei,Zhang, Yuhua,Yang, Xing,Birman, Vladimir B.
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experimental part
p. 1722 - 1737
(2012/04/04)
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- Immobilization and chromatographic evaluation of novel regioselectively substituted amylose-based chiral packing materials for HPLC
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The regioselectively substituted amylose derivatives bearing a 4-tert-butylbenzoate or 4-chlorobenzoate group at 2-position, and 3,5-dichlorophenylcarbamate and a small amount of 3-(triethoxysilyl) propylcarbamate groups at 3- and 6-positions were synthesized by a two-step process based on the esterification of 2-position of a glucose unit. The obtained derivatives were effectively immobilized onto macroporous silica gel by intermolecular polycondensation of triethoxysilyl groups. Their chiral recognition abilities were evaluated as chiral packing materials (CPMs) for high-performance liquid chromatography. These CPMs showed high chiral recognition as well as the conventional coated-type CPM, and can be used with the eluents-containing chloroform and tetrahydrofuran. With the extended use of these eluents, improvement of chiral recognition and reversed elution orders were realized. For some racemates, the immobilized CPM exhibited ability comparable or better to the commercial immobilized amylose- or cellulose-based columns,
- Shen, Jun,Li, Pengfei,Liu, Shuangyan,Shen, Xiande,Okamoto, Yoshio
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scheme or table
p. 878 - 886
(2012/06/30)
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- Separating agent for enantiomeric isomers
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The present invention provides a separating agent for enantiomeric isomers exhibiting high separation power. That is, the present invention provides a separating agent for enantiomeric isomers including, as an active ingredient, a polysaccharide derivative having at least part of hydrogen atoms of hydroxyl groups of a polysaccharide such as cellulose or amylose substituted by at least one of atomic groups represented by the following general formulae (I) and (II): (in the formulae, R represents a substituted or unsubstituted aromatic group, or a linear, branched, or cyclic aliphatic group).
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Page/Page column 7; 8; 9
(2010/04/23)
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- NEW CHIRAL STATIONARY PHASES FOR CHROMATOGRAPHY BASED ON AROMATIC ALLYL AMINES
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New chiral stationary phases (CSPs) based on chiral selectors covalently bound on a solid support were prepared. Chiral selectors were obtained from enantiomerically pure aromatic amines and 3,5-dinitrobenzoic acid and then linked to the support surface through the allylic double bond. Such obtained materials allow enantioseparation of racemates or enantiomerically enriched compounds. These chiral stationary phases can be used as fillings in chromatographic columns for enantiomer separation of naproxen type drugs and other similar non-steroidal anti-inflammatory drugs (NSAID) by means of high performance liquid chromatography on both the analytical and preparative scale.
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Page/Page column 16
(2009/10/22)
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- Filler for Optical Isomer Separation
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A polymer compound derivative, obtained by modifying part of the hydroxy or amino groups of a polymer compound having the hydroxy or amino groups with molecules of a compound represented by the following general formula (I): A-X—Si(Y)nR3-n (I), where A represents a reactive group which reacts with a hydroxy or amino group, X represents an alkylene group which has 1 to 18 carbon atoms and which may have a branch, or an arylene group which may have a substituent, Y represents a reactive group which reacts with a silanol group to form a siloxane bond, R represents an alkyl group which has 1 to 18 carbon atoms and which may have a branch, or an aryl group which may have a substituent, and n represents an integer of 1 to 3.
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Page/Page column 9; 11
(2009/05/28)
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- Di-2,2,2-trifluoro-1-(9-anthryl)ethyl fumarate, an easy starting point for the enantioselective preparation of trans-cyclohexene-4,5-dicarboxylate derivatives by Diels-Alder reaction
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Di-2,2,2-trifluoro-1-(9-anthryl)ethyl fumarate has been synthesized from fumaric acid and enantiopure Pirkle alcohol. The Diels-Alder reaction with different dienes employing different reaction conditions was assayed, with high diastereomeric excesses obtained. The structure and geometry of the cycloadducts was analyzed by NMR, molecular mechanics and X-ray diffraction. Hydrolysis made it possible to obtain the enantioenriched trans-cyclohexene-4,5-dicarboxylate derivatives and allow us to recover chiral auxiliary.
- Palomino-Schaetzlein, Martina,Virgili, Albert,Jaime, Carlos,Molins, Elies
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p. 3237 - 3243
(2007/10/03)
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- SEPARATING AGENT FOR OPTICAL ISOMER AND METHOD FOR PREPARATION THEREOF
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To provide a separating agent which combines a high optical resolving power inherent in polysaccharide derivatives with sufficient solvent resistance and a method with which the separating agent can be produced efficiently in short steps. The separating agent for enantiomeric isomers is characterized in that a polymerizable polysaccharide derivative of a polysaccharide derivative having polymerizable functional groups and a polymerizable monomer having polymerizable unsaturated groups are copolymerized with a carrier having polymerizable functional groups to be chemically bound mutually. The separating agent is preferably used for high performance liquid chromatography (HPLC), and is excellent in solvent resistance.
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Page/Page column 7-8
(2010/02/10)
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- THERMALLY IMMOBILIZED POLYSACCHARIDE DERIVATIVES
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The invention essentially relates to thermally crosslinked polysaccharide derivatives which contained no polymerizable functional groups prior to crosslinking and which are used in particular as support materials for the chromatographic separation of enantiomers. The present invention relates to thermally crosslinked polysaccharide derivatives in which the OH groups, as OR groups, have been esterified or converted into a carbamate (urethane), or mixtures of these, with the proviso that the OR groups contained no polymerizable double bonds prior to crosslinking. The thermally crosslinked polysaccharides according to the invention in conditioned form can also be used as pure polymers for the chromatographic separation of enantiomers.
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Page 8; 10; 12
(2008/06/13)
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- Crosslinked three-dimensional polymer network, method for preparing same, support material comprising same and uses thereof
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The invention concerns a crosslinked optically active three-dimensional polymer network, consisting of homochiral units of a first selector and of homochiral units of at least a second selector of different structure from the first selector, the homochiral units of the first selector comprising at least three polymerisable or crosslinkable functional groups and the homochiral units of the second selector comprising at least two polymerisable or crosslinkable functional groups, the homochiral groups being chemically mutually bound. The invention also concerns a method for making such a polymer network and its uses.
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Page/Page column 7-8
(2010/02/09)
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- New chiral borohydride based reducing agent: Asymmetric reduction of 9-anthryl trifluoromethyl ketone and other carbonyl compounds
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(S)-(+)-2-(α-Hydroxybenzyl)benzimidazole and (S)-(-)-2-benzimidazole-1-ethanol were synthesised and converted to chiral borohydrides which reduced prochiral ketones to the corresponding chiral alcohols in high yields (80 to 100%, e.e. 42 to 95%). This is the first report of sodium borohydride modified by 1,2-amino alcohol.
- Maiti, Dilip K.,Bhattacharya, Pranab K.
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- Flash Chiral Chromatography using Carbohydrate Carbamate-coated Silica
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Enantiomers of many chiral compounds are resolved rapidly on a preparative scale by passage through a column packed with flash chromatography silica which has been physically coated with a carbohydrate carbamate.
- Matlin, Stephen A.,Grieb, Sally J.,Belenguer, Ana M.
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p. 301 - 302
(2007/10/02)
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- Chiral Synthesis Via Organoboranes. 38 Selective Reductions. 48. Asymmetric Reduction of Trifluoromethyl Ketones by B-Chlorodiisopinocampheylborane in High Enantiomeric Purity
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(-)-B-Chlorodiisopinocampheylborane TM,1>, introduced by us several years ago, has been shown to reduce prochiral aryl and alkyl perfluorinated ketones to the corresponding optically active alcohols in very high ee.For example, 2,2,2-trifluoroacetophenone, trifluoroacetyl-1-naphthalene, and trifluoroacetyl-2-naphthalene are all reduced with 1 within 1-3 d at rt in 90percent ee, 78percent ee and 91percent ee, respectively.The optical purity of 1-phenyl-2,2,2-trifluoroethanol is upgraded to = 99percent ee by crystallizing the initially formed products from pentane. 1,1,2,2,2- pentafluoropropiophenone and 1,1,2,2,3,3,3-heptafluorobutyrophenone are reduced in 3 d with 1 to the corresponding alcohols in 92percent ee and 87 percent ee, respectively.The reagent reduces alkyl trifluoromethyl ketones at a rate faster than that of the aryl derivatives, while still providing the product alcohols in very high ee.Thus, 1,1,1-trifluoroacetone, 1,1,1-trifluorononan-2-one, and 1,1,1-trifluorodecan-2-one are all reduced within 4 - 8 h in 89percent ee, 92percent ee, and 91percent ee, respectively.Even α-sec-alkyl trifluoromethyl ketones are handled by 1 very efficiently.Thus cyclohexyl trifluoromethyl ketone is reduced by 1 at rt in 12 h to the product alcohol in 87percent ee.In all of these cases the trifluoromethyl group acts as the enantiocontrolling larger group as compared to the aryl or alkyl group.This produces alcohol products with stereochemistry opposite to those obtained for the corresponding hydrogen analogs.The steric and electronic influence of the trifluoromethyl group in achieving enantiocontrol in assymmetric reductions is discussed.Keywords: asymmetric reduction; trifluoromethyl ketones; DIP-Chloride; high enantiomeric purity
- Ramachandran, P. Veeraraghavan,Teodorovic, Aleksandar V.,Brown, Herbert C.
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p. 1725 - 1738
(2007/10/02)
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- Optical Resolution on Regioselectively Carbamoylated Cellulose and Amylose with 3,5-Dimethylphenyl and 3,5-Dichlorophenyl Isocyanates
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The optical resolving ability of two types of regioselectively carbamoylated cellulose and amylose with 3,5-dimethylphenyl and 3,5-dichlorophenyl isocyanates was evaluated.One had 3,5-dimethylphenylcarbamate groups at the 2 and 3 positions and a 3,5-dichlorophenylcarbamate group at the 6 position; the other had 3,5-dichlorophenylcarbamate groups at the 2 and 3 positions and a 3,5-dimethylphenylcarbamate group at the 6 position.In cellulose derivatives, the side chains at the 2,3, and 6 positions seem to interact complicatedly with racemates.On the other hand, in the amylose derivatives, the side chains at the 2 and 3 positions may mainly influence the chiral recognition ability.The optical resolving abilities of the cellulose and amylose derivatives having irregularly either 3,5-dimethylphenyl- or 3,5-dichlorophenylcarbamate groups at the 2,3 and 6 positions were also examined.
- Kaida, Yuriko,Okamoto, Yoshio
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p. 2225 - 2232
(2007/10/02)
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