Optical Rotation Measurements Research Articles

A fiber link equipment for the optical rotation measuring based on AC-DC modulation magneto-optical effect

Based on the magnetic-optical effect, an alternating current-direct current (AC-DC) two-stage modulation is applied in the newly developed equipment, which measures the concentration of solution through the optical rotation of optical active substance. A Faraday coil is combined with the AC-DC signal generator controlled by a pulse width modulation controller. To deduct the measuring error caused by the AC modulation or the DC modulation, a two-stage method based on the Superposition of DC component and AC component is demonstrated, which is characterized by removing the interference of the bigger magnetic rotation angle in the AC modulation alone. The tartaric acid, glucose, and sucrose sugar solutions are taken as the standard examples in testifying the equipment. A linear correlation is found between the measured optical rotation angle and the concentration of the solution, with the optical rotation angle being within a 1% margin of error and the maximum relative error smaller than 0.005g/ml. The results show that the equipment has the advantage of high precision, high integration, and strong anti-interference capacity. The fiber link makes the equipment portable and compact. The AC-DC two-stage modulation equipment can potentially be used in the optical rotation measurement.

Use of liquid chromatography- quadrupole time-of-flight mass spectrometry for enantioselective separation and determination of pyrisoxazole in vegetables, strawberry and soil

The present work firstly described the enantio-separation and determination of pyrisoxazole enantiomers in vegetables, strawberry and soil samples by chiral liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (LC-Q-TOF/MS). Pyrisoxazole has two chiral carbon atoms and consists of four stereoisomers. Taking the specific optical rotation measurement and MS analysis data into consideration, the four enantiomers were discriminated as (−)-A, (+)-A, (+)-B and (−)-B corresponding to their elution order under the optimum chromatographic condition. Influences of the mobile phase and column temperature on the enantio-separation selectivity of pyrisoxazole were explored. The perfect baseline separation of pyrisoxazole enantiomers can be achieved within 10min using methanol- water (70:30, v/v) as mobile phase on chiral Lux Cellulose-3 column. The thermodynamic analysis demonstrated that the enantioseparation of (−)-A and (+)-A, (+)-A and (+)-B were enthalpy driven separation, while the enantioseparation of (+)-B and (−)-B was entropy driven separation. Under the optimum method, method validation including matrix effect, linearity, sensitivity and precision were performed. At the spiked concentration of 10, 50 and 100μgkg−1, the recoveries of the pyrisoxazole enantiomers in cucumber, tomato, pakchoi, pepper and strawberry samples were 64.2–100% (RSD≤14%); While they were relatively higher in soil samples and all around 120% (RSD ≤10%). The limits of detection are in the range from 0.2 to 1.0μgkg−1 for cucumber, tomato, pakchoi, pepper, strawberry and soil samples. The developed method was then utilized for monitoring the degradation kinetics of pyrisoxazole enantiomers in strawberry under field trials, which provided the environmental behavior data of chiral pyrisoxazole enantiomers and consequently for further health risk assessment of the chiral pesticides.

Synthesis, structural characterization, docking, lipophilicity and cytotoxicity of 1-[(1R)-1-(6-fluoro-1,3-benzothiazol-2-yl)ethyl]-3-alkyl carbamates, novel acetylcholinesterase and butyrylcholinesterase pseudo-irreversible inhibitors

In the current study, sixteen novel derivatives of (R)-1-(6-fluorobenzo[d]thiazol-2-yl)ethanamine were synthesized as acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitors. Chemical structures together with purity of the synthesized compounds were substantiated by IR, 1H, 13C, 19F NMR, high resolution mass spectrometry and elemental analysis. The optical activities were confirmed by optical rotation measurements. The synthesized compounds were evaluated for their AChE and BChE inhibitory activities. In addition, the cytotoxicity of the most active compounds was investigated against human cell lines employing XTT tetrazolium salt reduction assay and xCELLigence system allowing a label-free assessment of the cells proliferation. Our results demonstrated that the inhibitory mechanism was confirmed to be pseudo-irreversible, in line with previous studies on carbamates. Compounds indicated as 3b, 3d, 3l and 3n showed the best AChE inhibitory activity of all the evaluated compounds and were up to tenfold more potent than standard drug rivastigmine. The binding mode was determined using state-of-the-art covalent docking and scoring methodology. The obtained data clearly demonstrated that 3b, 3d, 3l and 3n benzothiazole carbamates possess high inhibitory activity against AChE and BChE and concurrently negligible cytotoxicity. In conclusion, our results indicate, that these derivatives could be promising in an effective therapeutic intervention for Alzheimer’s disease.

Three new oleanane-type triterpene saponins from Atractylis flava

Three new bidesmosidic saponins (1–3), along with thirteen known metabolites consisting of two flavonoids and eleven triterpenoids were identified in dichloromethane and n-butanol extracts of the whole plant Atractylis flava Desf. The saponins were characterized as 3-O-[β-d-glucuronopyranosyl]-28-O-[β-d-xylopyranosyl-(1→4)-α-l-rhamnopyranosyl-(1→2)-β-d-xylopyranosyl]-16α-hydroxygypsogenic acid (1), 3-O-[β-d-glucuronopyranosyl]-28-O-[β-d-xylopyranosyl-(1→4)-α-l-rhamnopyranosyl-(1→2)-α-l-arabinopyranosyl]-16α-hydroxygypsogenic acid (2), and 3-O-[β-d-galactopyranosyl-(1→2)-β-d-glucuronopyranosyl]-28-O-[((3-O-acetyl)-β-d-xylopyranosyl)-(1→4)-((2-O-acetyl)-α-l-rhamnopyranosyl)-(1→2)-β-d-xylopyranosyl]-quillaic acid (3). Structures of all isolated compounds were elucidated by spectroscopic analysis, including 1D and 2D NMR (1H, 13C, COSY, HSQC, TOCSY, HSQC-TOCSY, HMBC, ROESY and NOESY), high-resolution electrospray ionization mass spectrometry (HRESIMS), acid hydrolysis, measurement of optical rotation and comparison with literature data.

Aspernolides F and G, new butyrolactones from the endophytic fungus Aspergillus terreus

Two new butyrolactones: aspernolides F (6) and G (7), together with three stigmasterol derivatives: (22E,24R)-stigmasta-5,7,22-trien-3-β-ol (1), stigmast-4-ene-3-one (2), and stigmasta-4,6,8(14), 22-tetraen-3-one (3), two meroterpenoids: terretonin A (4) and terretonin (5), and a butyrolactone derivative: butyrolactone VI (8) have been isolated from the endophytic fungus Aspergillus terreus isolated from the roots of Carthamus lanatus (Asteraceae). Their structures were determined by spectroscopic means (1D, 2D NMR, and HRESIMS), as well as optical rotation measurement and comparison with literature data. The isolated compounds were evaluated for their anti-microbial, anti-malarial, anti-leishmanial, and cytotoxic activities. Compound 1 displayed a potent activity against MRSA and C. neoformans with IC50 values of 0.96μg/mL and 4.38μg/mL, respectively compared to ciprofloxacin (IC50 0.07μg/mL) and amphotericin B (IC50 0.34μg/mL), respectively. While, 6 showed good activity against C. neoformans (IC50 5.19μg/mL) and mild activity against MRSA (IC50 6.39μg/mL). Moreover, 1 and 2 exhibited very good anti-leishmanial activity towards L. donovani with IC50 values of 4.61 and 6.31μg/mL, respectively and IC90 values of 6.02 and 16.71μg/mL, respectively.

Chiral cavity ring down polarimetry: Chirality and magnetometry measurements using signal reversals.

We present the theory and experimental details for chiral-cavity-ring-down polarimetry and magnetometry, based on ring cavities supporting counterpropagating laser beams. The optical-rotation symmetry is broken by the presence of both chiral and Faraday birefringence, giving rise to signal reversals which allow rapid background subtractions. We present the measurement of the specific rotation at 800 nm of vapors of α-pinene, 2-butanol, and α-phellandrene, the measurement of optical rotation of sucrose solutions in a flow cell, the measurement of the Verdet constant of fused silica, and measurements and theoretical treatment of evanescent-wave optical rotation at a prism surface. Therefore, these signal-enhancing and signal-reversing methods open the way for ultrasensitive polarimetry measurements in gases, liquids and solids, and at surfaces.

Terrenolide S, a new antileishmanial butenolide from the endophytic fungus Aspergillus terreus

Terrenolide S, a new butenolide derivative (6), together with six known compounds: (22E,24R)-stigmasta-5,7,22-trien-3-β-ol (1), stigmast-4-ene-3-one (2), stigmasta-4,6,8(14),22-tetraen-3-one (3), terretonin A (4), terretonin (5) and butyrolactone VI (7) have been isolated from the endophytic fungus Aspergillus terreus isolated from the roots of Carthamus lanatus (Asteraceae). Their structures were established by extensive spectroscopic analyses (1D, 2D NMR and HRESIMS), as well as optical rotation measurement and comparison with literature data. Compound 1 displayed a potent activity towards methicillin-resistant Staphylococcus aureus (MRSA) and Cryptococcus neoformans with IC50 values of 2.29 and 10.68 µM, respectively. Moreover, 1, 2 and 6 exhibited antileishmanial activity towards Leishmania donovani with IC50 values of 11.24, 15.32 and 27.27 µM, respectively and IC90 values of 14.68, 40.56 and 167.03 µM, respectively.

Cucumin S, a new phenylethyl chromone from Cucumis melo var. reticulatus seeds

A new phenylethyl chromenone, cucumin S [(R)-5,7-dihydroxy-2-[1-hydroxy-2-(4-hydroxy-3-methoxyphenyl)ethyl]chromone] (1), along with five known compounds: 5,7-dihydroxy-2-[2-(4-hydroxyphenyl)ethyl]chromone (2), 5,7-dihydroxy-2-[2-(3,4-dihydroxyphenyl)ethyl]chromone (3), luteolin (4), quercetin (5), and 7-glucosyloxy-5-hydroxy-2-[2-(4-hydroxyphenyl)ethyl]chromone (6) were isolated from the EtOAc fraction of Cucumis melo var. reticulatus Ser., Cucurbitaceae, seeds. Their structures were determined by spectroscopic means (1D and 2D NMR), as well as HRESIMS, optical rotation measurement, and comparison with literature data. The isolated compounds 1–6 were assessed for their antioxidant activity using DPPH assay. Compounds 3, 4, and 5 showed potent activities compared to propyl gallate at concentration 100μM.

Synthesis, structural characterization, antimicrobial and antifungal activity of substituted 6-fluorobenzo[d]thiazole amides

A series of novel 1-[(1R)-1-(6-fluoro-1,3-benzothiazol-2-yl)ethyl]-3-substituted phenyl amides was synthesized by the condensation reaction of (1R)-1-(6-fluoro-1,3-benzothiazol-2-yl)ethanamine with substituted benzoyl chlorides under mild conditions. Their structures were confirmed by 1H NMR, 13C NMR and 19F NMR spectra, elemental analyses and in three cases also by single-crystal X-ray diffraction techniques. The optical activities were confirmed by optical rotation measurements. All the synthesized compounds were screened for antibacterial and antifungal activity against a variety of bacterial and fungal strains. Some of the compounds reveal antibacterial and antifungal activity comparable or slightly better to that of chloramphenicol, cefoperazone and amphotericin B used as medicinal standards.

Dynamic Formation of Noncovalent Calixsalen Aggregates.

A procedure for studying "dynamic structural behavior" of large chiral macrocycles is presented. Ion mobility MS, diffusion-ordered NMR spectroscopy (DOSY NMR), and optical rotation (OR) measurements, supported by calculations, are used together as effective complementary methods to study dynamic formation of noncovalent aggregates. It is shown that the monomer-dimer equilibrium is driven by π-π or CH-π interactions and controlled largely by the substitution pattern of the calixsalen skeleton.

Optically active, magnetic microspheres: Constructed by helical substituted polyacetylene with pendent prolineamide groups and applied as catalyst for Aldol reaction

This article reports on the preparation of a novel category of optically active magnetic microspheres (OAMMPs) consisting of Fe3O4 nanoparticles and helical substituted polyacetylene bearing pendent prolineamide groups and the use of them for asymmetric direct Aldol reactions. The microspheres (200–300μm in diameter) were prepared by using chiral acetylenic monomer and alkynyl-Fe3O4 nanoparticles via suspension polymerization approach. They were obtained in high yield (>99%) with regular spheric morphology and exhibited noticeable optical activity, according to circular dichroism spectra and specific optical rotation measurements. The microspheres further served as chiral catalyst for performing direct Aldol reactions between acetone and p-nitrobenzaldehyde, providing the product in moderate yield (68%) and ee (75%). The magnetic microspheres can be easily recycled and reused. Mechanism for the asymmetric catalysis of Aldol reaction was further proposed.

High sensitive measurement of optical rotation based on photo-elastic modulation

In order to realize the continuous and stable, high speed, high precise and high sensitive measurement of optical rotation, and considering the application advantages of photo-elastic polarization modulation technology with high modulation frequency, high modulation purity, high modulation accuracy and good modulation stability, a new scheme about the measurement of optical rotation based on photo-elastic modulation is presented. Probe laser orderly passes through a polarizer, the rotation sample to be measured, a photo-elastic modulator, and a analyzer, and finally reaches the detector, this system uses less optical devices than any others previously reported, so it considerably reduces the measurement error that may be introduced by the optical devices. In the detecting of light path, the polarization axes of the polarizer and analyzer are respectively adjusted with respect to the photo-elastic modulator's fast axis directions 0° and 45°, the optical arrangements make the rotation angle to be measured appear in the alternating current signal, and the photo-elastic modulator's residual birefringence only appears in the odd harmonics. Consequently, the second harmonic signal of photo-elastic modulation is selected as the object to study, which effectively avoids the influence of residual birefringence of the photo-elastic modulator on optical rotation measurement, and efficiently improves the accuracy of optical rotation measurement. What is more, the detector output signal is separated into two parts, the direct current and alternating current signal. The alternating current signal is amplified, then outputs by a lock-in amplifier, which enhances the measurement sensitivity further. A ingenious verification test experiment is done, firstly, the probe laser is modulated into circularly polarized light, and then precisely rotates the polarizer to replace the optical rotation sample. The results show that the new scheme is feasible, this experiment gives the proportion coefficient of the measurement system, the sensitivity of optical rotation measurement increasing up to 3.15× 10-7 rad, and the measurement precision exceeding 0.3%. Therefore, in this scheme achieved is a high sensitive and precise measurement of optical rotation, and it is expected to be applied to the high sensitive and precise rotation measurement. The verification test experiment designed by us can also provide a outstanding calibration reference for high sensitive rotation measurement system.

Chiral imprinting in molten gallium

The question of the possibility of imprinting chirality in molten metals was addressed in the current paper. By optical rotation and CD measurements we have shown that chirality was indeed imprinted in molten Ga.

Synthesis and properties of chiral internally branched PAMAM-dendrimers

Improved synthetic methodology for the synthesis of internally branched chiral poly(amidoamine) (PAMAM) dendrons and dendrimers has been developed and the compounds have been characterized by NMR spectroscopy, IR spectroscopy, and optical rotation measurements. The dendrons and dendrimers show increased degree of internal hydrogen bonding upon increasing generation and the presence of different types of amide-protons in the compounds is indicative of the existence of a tertiary structure in these PAMAM-dendrimers.

Circular polarization interferometry: circularly polarized modes of cholesteric liquid crystals.

We describe a novel polarization interferometer which permits the determination of the refractive indices for circularly-polarized light. It is based on a Jamin-Lebedeff interferometer, modified with waveplates, and permits us to experimentally determine the refractive indices nL and nR of the respectively left- and right-circularly polarized modes in a cholesteric liquid crystal. Whereas optical rotation measurements only determine the circular birefringence, i.e. the difference (nL - nR), the interferometer also permits the determination of their absolute values. We report refractive indices of a cholesteric liquid crystal in the region of selective (Bragg) reflection as a function of temperature.

Chiroptical Signatures of Planar and Central Chirality in [2]Paracyclo[2](5,8)quinolinophane Derivatives

AbstractElectronic and vibrational circular dichroism (ECD and VCD) spectra and specific optical rotation measurements at the sodium D‐line (OR) have been taken for thirteen chiral [2]paracyclo[2](5,8)quinolinophane derivatives and calculated by density functional theory. Besides the planar chirality from the paracyclophane moiety in all molecules, some of the investigated compounds also exhibit central chirality due to an asymmetric carbon atom in the side‐chain bound at C‐2 of the heterocyclic ring. Characteristic bands for each type of chirality were clearly identified in the VCD spectra in the CH‐stretching and mid‐IR regions, allowing assignment of absolute and relative configurations. ECD was found to be sensitive mostly, if not exclusively, to planar chirality, whereas OR was also very sensitive to central chirality. Configurational assignment of the different diastereomers by the present method provided results that are in agreement with those inferred from NOE‐NMR experiments.

Structural variations of arabinoxylans extracted from different wheat (Triticum aestivum) cultivars in relation to chapati-quality

Wheat varieties, such as DWR-162, GW-322 (good chapati making quality) and MACS-2496, HD-2189 (poor chapati making quality) were used to study the structural features of arabinoxylans. Structural features of the purified arabinoxylans were elucidated by a combination of methods such as methylation analysis, 13C-NMR, FT-IR, periodate oxidation, Smith degradation and optical rotation measurements. The results indicated a xylan backbone in β-(1–4) linkage, which is substituted at O-3 or at O-2 and O-3. Completely branched xylosyl residues were also observed in these wheat arabinoxylans. The wheat varieties known for good chapati making quality (DWR-162 and GW-322) revealed arabinoxylans with higher degree of branching pattern compared to those of poor wheat varieties such as MACS-2496 and HD-2189. Variations in the structural characteristics of arabinoxylans such as degree of branching pattern coupled with ferulic acid contents are of interest in wheat varieties differing in chapati making quality.

Determination of Sucrose Concentrates Using Ellipsometry Technique and Transmission Spectroscopy

In this paper, the ellipsometry based on polarization technique used to determination of sucrose concentrates. And then we used multi-wavelength radiation from a halogen lamp provided spectral, is described and applied to the determination of optically active of sucrose. The instrument has no moving parts, and optical rotation measurements are an apparent absorbance. Apparent absorbance measurements can be combined with over a wide spectral range. Results obtained by this two technique have showed good.

Chiral organoborane Lewis pairs derived from pyridylferrocene.

In an effort to develop a new class of redox-active chiral Lewis pairs, pyridine and borane moieties with different steric and electronic properties were introduced onto a planar chiral 1,2-disubstituted ferrocene framework. Metathesis of lithiated, stannylated, or mercuriated pyridylferrocenes with boron halides afforded (pR)-2-[bis(pentafluorophenyl)boryl]-1-(3,5-dimethylpyrid-2-yl)ferrocene (4-Pf), (pR)-2-[dimesitylboryl]-1-(3,5-dimethylpyrid-2-yl)ferrocene (4-Mes), (pS)-2-(bis(pentafluorophenyl)boryl)-1-(2-trimethylsilylpyrid-6-yl)ferrocene (5-Pf), or (pS)-2-[dimesitylboryl]-1-(2-trimethylsilylpyrid-6-yl)ferrocene (5-Mes). The borylated products were analyzed by multinuclear NMR spectroscopy, HRMS, and single-crystal X-ray diffraction. Chiral HPLC and optical-rotation measurements were employed to assess the stereoselectivity of the borylation process and to establish the correct stereochemical assignments. The strength of the B-N interactions were investigated in solution and in the solid state. Compounds 4-Pf and 4-Mes formed robust 'closed' B-N heterocyclic systems that proved to be perfectly stable to air and moisture, whereas 5-Pf established a dynamic equilibrium, in which the B-N heterocycle was observed exclusively at room temperature, but opened up at high temperature according to (19)F NMR exchange spectroscopy data. As a consequence, 5-Pf reacted readily with a molecule of water to generate a ring-opened pyridinium borate. The combination of bulky borane and bulky pyridyl groups in 5-Mes led to a completely 'open' frustrated Lewis pair system with uncomplexed pyridine and borane groups, even at room temperature. Electrochemical studies were performed and the effect of preparative ferrocene oxidation on the structural features was also explored.

Fundamentals of cavity-enhanced polarimetry for parity-nonconserving optical rotation measurements: Application to Xe, Hg, and I

We present the theoretical basis of a cavity-enhanced polarimetric scheme for the measurement of parity-nonconserving (PNC) optical rotation. We discuss the possibility of detecting PNC optical rotation in accessible transitions in metastable Xe and Hg, and ground state I. In particular, the physics of the PNC optical rotation is presented, and we explore the lineshape effects on the expected PNC optical rotation signals. Furthermore, we present an analysis of the eigenpolarizations of the cavity-enhanced polarimeter, which is necessary for understanding the measurement procedure and the ability of employing robust background subtraction procedures using two novel signal reversals. Using recent atomic structure theoretical calculations, we present simulations of the PNC optical rotation signals for all proposed transitions, assuming a range of experimentally feasible parameters. Finally, the possibility of performing sensitive measurements of the nuclear-spin-dependent PNC effects is investigated, for the odd-neutron nuclei $^{129}$Xe and $^{199}$Hg, and the odd-proton nucleus $^{127}$I.