Relative stereochemistries of the ether rings and sugar moieties in durinskiol A

Durinskiol A (1) is a long carbon-chain polyol compound with a molecular weight of 2128 mu isolated from the symbiotic dinoflagellate Durinskia sp. The relative stereochemistries of ether rings and sugar moieties in 1 were established based on 2D-NMR analysis and molecular modeling studies. Conformational analysis of the 6,5,6-bis-spiroacetal ring in 1 was also examined by using ab initio methods.     

Photoinduced Charge‐Transfer State of 4‐Carbazolyl‐3‐(trifluoromethyl)benzoic Acid: Photophysical Property and Application to Reduction of Carbon−Halogen Bonds as a Sensitizer

The photoinduced persistent intramolecular charge‐transfer state of 4‐carbazolyl‐3‐(trifluoromethyl)benzoic acid was confirmed. It showed a higher catalytic activity in terms of yield and selectivity in the photochemical reduction of alkyl halides compared to the parent carbazole. Even unactivated primary alkyl bromides could be reduced by this photocatalyst. The high catalytic activity is rationalized by considering the slower backward single‐electron transfer owing to the spatial separation of the donor and acceptor subunits.     

A validated LC‐MS/MS method for the determination of canagliflozin,a sodium–glucose co‐transporter 2 (SGLT‐2) inhibitor,in a lower volume of rat plasma: application to pharmacokinetic studies in rats

Canagliflozin is a novel, orally selective inhibitor of sodium‐dependent glucose co‐transporter‐2 (SGLT2) for the treatment of patients with type 2 diabetes mellitus. In this study, a validated liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method for the quantitative analysis of canagliflozin in a lower volume of rat plasma (0.1 mL) was established and applied to a pharmacokinetic study in rats. Following liquid–liquid extraction by tert‐butyl methyl ether, chromatographic separation of canagliflozin was performed on a Quicksorb ODS (2.1 mm i.d. × 150 mm, 5 µm size) using acetonitrile–0.1% formic acid (90:10, v/v) as the mobile phase at a flow rate of 0.2 mL/min. The detection was carried out using an API 3200 triple‐quadrupole mass spectrometer operating in the positive electrospray ionization mode. Selected ion monitoring transitions of m/z = 462.0 [M + NH₄]⁺ → 191.0 for canagliflozin and m/z = 451.2 [M + H]⁺ → 71.0 for empagliflozin (internal standard) were obtained. The validation of the method was investigated, and it was found to be of sufficient specificity, accuracy and precision. Canagliflozin in rat plasma was stable under the analytical conditions used. This validated method was successfully applied to assess the pharmacokinetics of canagliflozin in rats using 0.1 mL rat plasma. Copyright © 2016 John Wiley & Sons, Ltd.     

Formation and Physicochemical Features of Hybrid Threadlike Micelles in Aqueous Solution

We investigate the construction of long, stable hybrid threadlike micelles consisting of polyelectrolytes and oppositely charged surfactants in aqueous solution and examine the physicochemical features such as their structure and viscoelastic behavior in aqueous solution. The most important point for their construction is the careful control of interactions, especially electrostatic interactions, caused between the surfactants and polyelectrolytes. Incorporated polyelectrolytes are fully extended in these hybrid threadlike micelles irrespective of the molecular weight of the polymer. The viscoelastic behavior of the hybrid threadlike micellar solution is similar to that of ordinary threadlike micellar systems consisting of low‐molecular‐weight substances. However, the inclusion of polymers in the micelles causes differences in their mechanical properties.     

The characteristic fragment ions and visualization of cationic starches on pulp fiber using ToF‐SIMS

Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) was used to investigate the distribution of cationic starch on pulp fiber. To identify the characteristic fragment ions of the cationic starches, deuterium‐labeled cationic starches were prepared and analyzed using ToF‐SIMS. The starch 2‐hydroxypropyltrimethylammonium chloride derivative generated characteristic fragments at m/z 58 and 59, which were identified as [H₂C?N(CH₃)₂]⁺ and [N(CH₃)₃]^+·, respectively. The fragmentation patterns were also suggested. From the imaging analysis, the adsorption of the cationic starch on fibers was uneven on individual fibers, as well as between fibers. This may have been on account of fiber morphology and structure. On examining scanning electron microscope (SEM) images, the quaternary ammonium starch derivative (QS) did not penetrate the fiber. No migration of cationic starch was observed under various drying conditions. Copyright © 2007 John Wiley & Sons, Ltd.     

Morphological variation in a toroid generated from a single polymer chain

A single semiflexible polymer chain folds into a toroidal object under poor solvent conditions. In this study, we examined the morphological change in such a toroidal state as a function of the cross-sectional area and stiffness of the chain together with the surface energy, which characterizes the segmental interaction parameter. Changes in the thickness and outer/inner radius on a toroid are interpreted in terms of these parameters. Our theoretical expectation corresponds to the actual morphological changes in a single giant DNA molecule as observed by electron microscopy.     

Feeding attractants for the muricid gastropod Drupella cornus, a coral predator

The muricid gastropods genus Drupella are known to be voracious coral predator. Outbreaks of them have accelerated significant destruction on coral reefs, but its precise mechanism is poorly understood. Here, we describe the identification of montiporic acids C (1) and A (2) isolated from sea water extracts of the coral Montipora sp., which showed potent feeding-attractant activity toward D. cornus.     

Photopolymerization mechanisms of acrylates in poly(methyl methacrylate) films

Photoinitiation processes for photopolymer coating layers have been investigated with respect to quenching rates by a laser flash photolysis using a total reflection cell, as well as to the decomposition‐quantum yield of a sensitizer dye and a radical‐generating reagent by a gel permeative chromatographic analysis (GPC); the sensitizer dye,2‐[p‐(diethylamino)styryl]naphtho[1,2‐d]‐thiazole (DNT) and the radical‐generating reagent, 2,2′‐bis(2‐chlorophenyl)‐4,4′,5,5′‐tetraphenyl‐1,1′‐bi‐1H‐imidazole (BI). From experiments using flash photolysis, strong fluorescence was observed at excitation of 355 nm laser pulse, though no transient absorption was observed. The fluorescence was statically quenched by BI with a quenching distance, R = 11 Å. From the experiments using GPC, the high‐quantum yield of decomposition (Φ) was obtained as Φ (DNT) = 3 and Φ (BI) = 9 for DNT and BI in the presence of acrylate monomers, trimethyrolpropanetri‐acrylate (TMPTA), at 488 nm exposure of 3.36 mJ cm which was required to form a photo‐hardened image, however no decomposition of DNT and BI was detected in the absence of TMPTA. The results imply that the photoinitiator system undergoes efficient static‐dye sensitization and efficient polymerization of the acrylate monomers accompanied with the chain decomposition of DNT and BI. Copyright © 1999 John Wiley & Sons, Ltd.     

Stepwise and dramatic enhancement of anion recognition with a triple-site receptor based on the calix[4]arene framework using two different cationic effectors

Synthesis and binding behavior of a novel multi-responsive host 1, in which two esters, two polyether moieties, two urea sites, and two bipyridine units as ion binding sites are arranged on the calix[4]arene skeleton, is reported. 1 recognizes Na(+) and Ag(+) simultaneously and quantitatively and captures an anionic guest. The ability of 1 to recognize anions, including CF(3)SO(3)(-) and BF(4)(-), remarkably increases in a stepwise manner using Na(+) and Ag(+) as effectors. The enhancement of the K(a) eventually reaches factors of 1500 and 2000 for NO(3)(-) and CF(3)SO(3)(-), respectively, in the presence of both Na(+) and Ag(+), compared to the free 1. The regulation of binding of multiple ligands may be applicable to multistep cascade systems for the amplification of molecular events, and further studies in this field could provide insight applicable to more advanced molecular devices.