1H NMR determination of absolute configuration of 1- or 2-aryl-substituted alcohols and amines by means of their diastereomers: novel separation technique of diastereomeric derivatives of pyridyl alcohols by extraction

A convenient method to determine the absolute configuration of trans-2-aryl cyclohexanols, 1-aryl alcohols and amines was achieved. This method takes advantage of the 1H NMR spectroscopic observations of the remarkable high-field shift of C18-CH3 protons caused by the aromatic shielding effect. It is based on a discrimination of the difference of the environments in two diastereomers derived from 3 beta-acetoxy-5-etienic acid. Furthermore, it was observed that the corresponding diastereomeric derivatives of the pyridyl alcohols were simply separated by extraction based on the difference in their basicity.     

Organometallic Compounds XIV. Formation of novel [4]ferrocenophanes by the acid-catalyzed reaction of 1,1′-bis (α-hydroxy-α-phenylethyl) ferrocene

The acid-catalyzed reaction of 1,1′-bis(α-hydroxy-α-phenylethyl)ferrocene gave several [4] ferrocenophanes including a peroxide derivative. Their structures have been confirmed by spectrometric methods and from a study of their reaction behavior.     

Optical resolution of (±)-1-furo[2,3-c]pyridin-5-yl-ethanol using extraction technique: formal total synthesis of PNU-142721, HIV-1 reverse transcriptase inhibitor

A formal total synthesis of PNU-142721 was effectively carried out to prepare the chiral non-racemic synthon 1-furo[2,3-c]pyridin-5-yl-ethanol. It was easily obtained utilizing the optical resolution of the corresponding diastereomeric derivatives derived from 3β-acetoxyetienic acid by using the extraction technique.     

Thermosensitive copolymers having soluble and insoluble monomer units,poly(N‐vinylacetamide‐co‐methyl acrylate)s: Effect of additives on their lower critical solution temperatures

New thermosensitive polymers were synthesized by copolymerization between N‐vinylacetamide (NVA) and methyl acrylate whose homopolymers are soluble and insoluble in water, respectively. The lower critical solution temperature (LCST) of the obtained copolymers ranged between 59 and 83 °C, and the LCST increased with an increasing NVA content in the copolymers. The effectiveness of various salts addition on lowering the LCST of the copolymer solutions followed Hoffmeister series. NaCl and Na₂SO₄ addition linearly lowered the LCST with an increasing salts concentration, and slopes of the lines were almost constant regardless of the copolymer composition. The effectiveness of alcohols with various alkyl chain lengths on lowering the LCST did not follow the viscosity B coefficient values of the alcohols, which was probably the result of preferential adsorption of the alcohols to the copolymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2651–2658, 2004     

Determination of dexamethasone in human plasma and urine by electron-impact mass spectrometry

A gas chromatographic-electron-impact mass spectrometric method for the determination of dexamethasone in biological fluids has been developed. Quantitation by isotopedilution mass spectrometry was carried out by selected-ion monitoring on the molecular ions of the tetra(trimethylsilyl) derivative of dexamethasone and of dexamethasone M+9 (m/z 680 and 689, respectively). The sensitivity, specificity, precision and accuracy of the method were demonstrated to be satisfactory for application to pharmacokinetic and bioavailability studies of dexamethasone after administration of a therapeutic dose.     

Enhancing the effect of the nanofiber network structure on thermoresponsive wettability switching

This letter reports the enhancing effects of a nanofiber network structure on stimuli-responsive wettability switching. Thermoresponsive coatings composed of nanofibers were prepared by electrospinning from thermoresponsive polymer poly(N-isopropylacrylamide) (PNIPAAm). The nanofiber coatings showed a large amplitude of thermoresponsive change in the wettability from hydrophilic to hydrophobic states compared to a smooth cast film. In particular, the combination of the surface chemistry and unique topology of the electrospun nanofiber coatings enables a transition from the Wenzel state to the metastable Cassie-Baxter state with an increase in temperature and consequently an enhanced amplitude of change in the water contact angles: the apparent contact angle differences between 25 and 50 °C are Δθ*(25-50?°C?)= 108 and 10° for the nanofiber coatings with a diameter of 830 nm and a smooth cast film, respectively. The fabrication of the 3D nanofiber network structure by electrospinning from stimuli-responsive materials is a promising option for highly responsive surfaces in wettability.     

Structure of Li2FeSiO4

A large-scale lithium-ion battery is the key technology toward a greener society. A lithium iron silicate system is rapidly attracting much attention as the new important developmental platform of cathode material with abundant elements and possible multielectron reactions. The hitherto unsolved crystal structure of the typical composition Li2FeSiO4 has now been determined using high-resolution synchrotron X-ray diffraction and electron diffraction experiments. The structure has a 2 times larger superlattice compared to the previous beta-Li3PO4-based model, and its origin is the periodic modulation of coordination tetrahedra.     

Soluble-insoluble-soluble transitions of aqueous poly(N-vinylacetamide-co-acrylic acid) solutions

Several poly(N-vinylacetamide-co-acrylic acid)s with various copolymer compositions have been synthesized, and their unique phase-transition behavior in aqueous salt (Na2SO4 or NaCl) solutions was investigated. Copolymers containing more than 51 mol % N-vinylacetamide (NVA) show reentrant soluble-insoluble-soluble transitions with increasing temperature. The soluble-insoluble transition temperature (T(p1)) increased linearly with increasing NVA content, whereas the insoluble-soluble transition temperature (T(p2)) was almost constant irrespective of the NVA content. Potentiometric titration of the copolymer solutions suggested that the acrylic acid (AA) carboxyl groups form hydrogen bonds with the NVA amide groups even under soluble conditions. Dehydration of the NVA amides and their consequent hydrogen bonding with the AA carboxyl groups during the soluble-insoluble transition process was indicated by FTIR measurements. Addition of salt (Na2SO4 or NaCl) to the aqueous media reduces the solvent quality and enhances the intra- and interchain interactions of the copolymers. Thus, T(p1) was observed to decrease and T(p2) was observed to increase with increasing salt concentration. However, the addition of urea to the media reverses the concentration dependence of T(p1) and T(p2) by disturbing the intra- and interchain interactions of the copolymers.     

Quantitative determination of regorafenib and its two major metabolites in human plasma with high‐performance liquid chromatography and ultraviolet detection

A simple, highly sensitive and specific high‐performance liquid chromatography (HPLC) method was developed for the simultaneous quantitation of regorafenib, N‐oxidemetabolite (M‐2) and the desmethyl N‐oxide metabolite (M‐5) in human plasma. Regorafenib, M‐2, M‐5 and the internal standard sorafenib were separated using a mobile phase of 0.5% KH₂PO₄ (pH 3.5)–acetonitrile (30:70, v/v), on a Capcell PAK MG II column at a flow rate of 0.5 mL/min and measurement at UV 260 nm. The lower limits of quantification for regorafenib, M‐2 and M‐5 were 10 ng/mL for each analyte. A procedure using solid‐phase extraction required only a small amount of plasma (100 μL) for one analysis while providing high extraction recovery (>81% for all compounds) and good selectivity. Coefficients of variation for intra‐ and inter‐day assays were <12.2% for regorafenib, <12.3% for M‐2 and <15.1% for M‐5. Accuracies for intra‐ and inter‐day assays were <9.4% for regorafenib, <8.0% for M‐2 and <12.8% for M‐5 over a linear range from 10 to 10,000 ng/mL. This HPLC assay is suitable for clinical pharmacokinetic studies of regorafenib. The present HPLC method is currently in use for our observational studies of patients under treatment. Copyright © 2016 John Wiley & Sons, Ltd.