All isolated metabolites were carefully screened by analytical TLC plates (Merck, Germany) under ultraviolet-visible detector with λ 254 nm. Separations were performed by silica gel (200–300 mesh, Yantai Chemical Co., Ltd., China), ODS (YMC Co., Japan), and Sephadex LH-20 (Mitsubishi Chemical Co., Japan) column chromatography. Generally, all target products were purified through an analytical HPLC (Shimadzu LC-10AVP Plus) with a RP-C18 column (5 μm, 10 × 250 mm, Welchrom®, China) and a CHIRALPAK®IC column (5 μm, 10 × 250 mm, Daicel, China). HRESIMS data were acquired by a Thermo Scientific LTQ-Orbitrap XL apparatus. IR spectra were measured on a Bruker Vertex 70 spectrophotometer using KBr discs. UV spectra were recorded using a Varian Cary 50 instrument. Circular dichroism chiroptical spectra were performed using a JASCO J-1700 spectrometer. The 1H (400 MHz) and 13C (100 MHz) NMR spectra were obtained using a Bruker AM-600 spectrometer with tetramethylsilane (TMS) as an internal standard while the chemical shifts were characterized to solvent peaks (CD3OD, δH 3.31 ppm; δC 49.15 ppm).
Chiralpak ic column
Manufactured by Daicel
Sourced in China, Japan
The Chiralpak IC column is a chiral stationary phase used for the separation and analysis of enantiomeric compounds. It is composed of amylose-derived chiral selector covalently bonded to a silica gel support. The column is designed to provide efficient and selective separation of a wide range of racemic mixtures.
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Lab products found in correlation
Ltq orbitrap xl apparatus, by Thermo Fisher Scientific (1 mentions)
Am 600 spectrometer, by Bruker (1 mentions)
Cary 50 instrument, by Agilent Technologies (1 mentions)
Micromass q tof micro synapt high definition mass spectrometer, by Waters Corporation (1 mentions)
Axs smart apex 2 single crystal x ray diffractometer, by Bruker (1 mentions)
Chiralcel od h, by Daicel (1 mentions)
Uflc 6 ad, by Shimadzu (1 mentions)
Welch ultimate xb c18, by Hill-Rom (1 mentions)
Lambda 35, by Bruker (1 mentions)
Rp 18, by Merck Group (1 mentions)
J 1500 spectrometer, by Jasco (1 mentions)
Vertex 70, by Bruker (1 mentions)
7 protocols using chiralpak ic column
1
Isolation and Characterization of Natural Metabolites
2
Chiral Separation of Astaxanthin Isomers
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The all-trans isomer of astaxanthin was purchased from SenBeiJia Biological Technology Co., Ltd. Chiral isomers of all-trans astaxanthin were prepared from the all-trans astaxanthin on a Hanbon NP700 semipreparative HPLC system (Hanbon Sci. & Tech., Jiangsu, China) equipped with a CHIRALPAK IC column (5 μm, 250 mm × 10 mm, Daicel Corporation, Japan). The binary mobile phase consisted of A: methyl tert-butyl ether (MTBE) and B: acetonitrile. The solvent gradient was as follows: 0-24 min, 55% B. Peaks were detected at 470 nm by an UV-vis detector. The flow rate was set at 3.0 mL/min. Under these conditions, the chiral isomers fractions at the retention times of 15.622 min, 17.878 min, 20.534 min were collected and dried under a nitrogen stream to give the 3S,3′S-, 3R,3′S-and 3R,3′R-all-trans astaxanthin separately, as shown in Figure 1. Figure 1 HPLC chromatograms of chiral isomers of all-trans astaxanthin For the Raman spectral recording, the AST-sample powders are placed on a quartz plate for the Raman detections. All the Raman spectra were recorded in the 200-3700 cm -1 region using XploRA Raman spectrometer. (HORIBA JOBIN YVON) The laser power at the sample was ca. 1.2 mW, and the exposure time was 5 s. The spectra were measured with at least three repeats, then they were averaged, baseline corrected, and normalized.
3
Chiral Separation of Enantiomers
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Chiralpak IC column, 250 mm × 4.6 mm I.D. with 5 µm particle size, was obtained from Daicel (Tokyo, Japan). The optimized chromatographic separation conditions were performed at 25 °C with the flow rate of 1 mL min−1. The detection was carried out at 230 nm. The hold-up time was measured by the first perturbation of the baseline. Retention or capacity factors, k′, were determined from (tR − t0)/t0, where tR is the retention time of analyte and t0 the hold-up time. Resolution, Rs, was calculated from 2(t2 − t1)/(W1 + W2), where t1 and t2 are the retention times of the successively eluted enantiomers, and W1 and W2 are the peak widths of the first and second eluted enantiomers, respectively. Enantioselectivity factor (α) was obtained from k2′/k1′, where k1′ and k2′ are the retention factors for the first and the second eluted enantiomer, respectively.
4
Chiral NMR and X-ray Analysis Protocol
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1H NMR (400 MHz), 13C NMR (100 MHz) and 19F NMR (376 MHz) spectra were recorded on Brucker Asend 400 spectrometers. HRMS was performed on Waters Micromass Q-TOF micro Synapt High Definition Mass Spectrometer. HPLC analysis using a chiral stationary phase was performed on Shimadzu or Dalian Elite (UV230+ UV/Vis Detector and P230P High Pressure Pump). CHIRALCEL OD-H or CHIRALPAK IC column was purchased from Daicel Chemical Industries, Ltd. Single-crystal X-ray diffraction data were recorded on Bruker-AXS SMART APEX II single-crystal X-ray diffractometer. See Supplementary Figs 1–62 for the NMR spectra and HPLC chromatograms, Supplementary Table 1 for the optimization of reaction, Supplementary Discussion for the mechanism studies and computational details and Supplementary Methods for the characterization data of compounds not listed in this part.
5
Enantioselective Epoxide Hydrolysis Assay
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Racemic benzyl glycidyl ether was added to 50 mM Tris pH 8.0 at a concentration of 20 mM in ethanol and reaction was initiated by addition of 36 μg of purified enzyme, kept at 30 °C up to 40 minutes in shaking water bath. At the end of the incubation time the reaction mix was extracted 1 : 1 with 95 : 5 hexane: isopropanol. The organic layer was injected on a Chiralpak IC column (250 × 4.6 μm, Daicel, Tokyo, Japan) in a isocratic mode with the mobile phase 95 : 5 hexane : isopropanol at room temperature with a flow rate of 0.5 ml min−1 at 240 nm on Shimadzu UFLC 6-AD. In order to detect the diol product in the reaction, reaction mixture was lyophilized completely, re-dissolved in isopropanol and then injected on Chiralpak IG-3 column (250 × 4.6 μm, Daicel, Tokyo, Japan) in a isocratic mode with the mobile phase 90 : 05 : 05 n-hexane : ethanol : methanol at 15 °C with a flow rate of 1 ml min−1 at 220 nm on Shimadzu UFLC 6-AD.
6
Enantioselective Synthesis of Trifluoromethylated Oxindole Derivative
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The reaction was carried out following the general procedure. 1H-NMR of the crude showed a 64% yield for catalyst I. The crude mixture was purified by flash column chromatography (hexane : EtOAc = 19 : 1) and the title compound was obtained as a yellowish oil in 93% enantiomeric excess. When the reaction was performed in 1 mmol scale the crude product showed a 68% yield based on 1H-NMR and 50% yield on the isolated pure product. The enantiomeric excess in this case was found to be 95%. The ee was determined by HPLC analysis on a Daicel Chiralpak IC column: hexane/i-PrOH 95 : 5, flow rate 1.0 mL min−1, λ = 254 nm: τV = 5.6 min, τI = 6.9 min. [α]25D + 376.5 (c 1.0, CHCl3). HRMS-ESI-ORBITRAP (+): calculated for [C26H26F3NNaO4]+ 496.1712, found 496.1721 [M + Na]+. 1H-NMR (400 MHz, CDCl3) δ 7.86–7.81 (m, 1H), 7.50 (d, J = 7.7 Hz, 1H), 7.42–7.27 (m, 6H), 7.16 (dd, J = 7.7 Hz, 1.1 Hz, 1H), 6.92 (d, J = 15.8 Hz, 1H), 6.24 (d, J = 16.3 Hz, 1H), 5.39 (s, 1H), 4.35 (d, J = 12.6 Hz, 1H), 2.83 (d, J = 12.6 Hz, 1H), 2.35 (s, 3H), 1.67 (s, 9H). 19F-NMR (376 MHz, CDCl3) δ −81.31. 13C-NMR (100 MHz, CDCl3) δ 168.7, 152.6, 148.8, 138.2, 135.9, 133.1, 128.8, 128.7, 128.2, 126.8, 124.2, 124.2, 123.7, 123.4, 114.7, 85.0, 78.0 (q, J = 28.2 Hz, tetrasubstituted aliphatic carbon, partially overlapped with CDCl3), 42.0, 28.1, 27.9.
7
Phytochemical Analysis Protocols
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Thin-layer chromatography (TLC) was conducted with HPTLC Silica gel 60 RP-18 F254s 25 Glass plates (Merck Millipore) and LuxPlate® silica gel 60 F254 (Merck, Germany). Silica gel (120–200 mesh; Qingdao Bang-Kai High and New Technology Co., LTD., China), Sephadex LH-20 (Pharmacia, America), and RP-18 (50 μm, Merck, Germany) were used for column chromatography. HPLC experiments were subjected to LC3050 Analysis of HPLC system (CXTH, Beijing, China) equipped with an UV 3000 detector and a semi-preparative column (5 μm, 10 × 250 mm, Welch Ultimate® XB-C18). Enantioseparation was achieved using a CHIRALPAKIC column (5 μm, 10 × 250 mm, Daicel Chiral Technologies Co., LTD., China). The HR-ESI-MS data were resolved in positive ion mode on a Thermo ScientificTM LTQ Orbitrap XLTM spectrometer. The UV and FT-IR spectra were recorded on a PerkinElmer Lambda 35 and Bruker Vertex 70 apparatus, respectively. A Hanon P810 automatic polarimeter was used to record the optical rotation values. The ECD spectra were measured on a JASCO J-1500 Spectrometer (JASCO, Japan). The NMR spectra were recorded on a Bruker AM-400/600 Spectrometer (Bruker, Switzerland) using tetramethylsilane (TMS) as an internal standard, and the 1H and 13C NMR data were normalized to the solvent peaks for methanol-d4 at δH 3.31 and δC 49.15.
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