Simple and rapid UV spectrophotometry of caffeine in tea coupled with sample pre-treatment using a cartridge column filled with polyvinylpolypyrrolidone (PVPP)

We have applied a sample pre-treatment method with a cartridge column filled with polyvinylpolypyrrolidone (PVPP) to the effective removal of polyphenols and simple UV spectrophotometry of caffeine in tea. The absorption maximum length (lambda(max)) for caffeine was close to those for tea catechins in aqueous 1% acetic acid; therefore, the UV spectrum of a non-treated green tea sample had a large absorption wave. In contrast, the absorbance of the green tea sample was gradually reduced by PVPP cartridge treatment using PVPP from 0 to 50 mg, and was nearly constant using a pre-treatment cartridge with more than 100 mg PVPP, because tea catechins were effectively removed and caffeine was mostly recovered from a green tea sample by means of PVPP cartridge treatment. The PVPP pre-treatment cartridge also removed polyphenols successfully from oolong and black tea samples. Comparison with conventional HPLC analysis indicated that the present pre-treatment method with a PVPP cartridge was useful for the simple and selective UV spectrophotometric determination of caffeine in green, oolong and black tea samples.     

Construction of the adamantane core of plukenetione-type polycyclic polyprenylated acylphloroglucinols

The construction of a highly functionalized adamantane core of plukenetione-type polycyclic polyprenylated acylphloroglucinols (PPAPs) is described. The method features the construction of the bicyclo[3.3.1]nonane core (3) by successive Michael reactions and the construction of the adamantane core of plukenetione-type PPAPs by acid-catalyzed cyclization of a bicyclo[3.3.1]nonane precursor (2).     

Fluorescence response of a 4-trifluoroacetylaminophthalimide to iodide ions upon 254 nm irradiation in MeCN

The title trifluoroacetylaminophthalimide derivative produced a violet fluorescence (lambdaFLmax 392 nm) in MeCN, and it displayed a green emission (lambdaFLmax 506 nm) after irradiation at 254 nm in the presence of iodide ions. The corresponding amidate ion of the trifluoroacetamide was identified as the green fluorescence emitter. The deprotonation reaction may be caused by proton-abstracting solvated electrons generated by a photochemical charge--transfer-to-solvent process from I(-) to MeCN.     

New Visualization Technique with a Three-Dimensional Video-Assisted Stereoendoscopic System: Application of the BVHIS Display Method During Endolaryngeal Surgery

A three-dimensional video-assisted stereoendoscopic system (3D video system) developed by the Shinko Optical Company, Ltd. (Tokyo, Japan), and referred to as the binocular vision by horizontal image shifting display method (BVHIS display method), has been developed to digitally process ordinary video signals obtained with a video camera connected to a direct videolaryngoscope. The three-dimensional video system provides the surgeon with stereoendoscopic video images and enhances the ability of the surgeon to perform delicate endoscopic procedures. The three-dimensional video-assisted stereoendoscopic laryngosurgical procedure and its underlying principles are described in this paper. A total of 12 patients with laryngeal lesions causing dysphonia underwent three-dimensional video-assisted stereoendoscopic laryngosurgery. Although the video image obtained with the BVHIS display method is only pseudo-three-dimensional, this method enables the surgeon to perceive both depth perception and realism. We describe a surgical procedure using this new visualizing technique and the underlying principles of the technique. Preoperative and postoperative evaluations of the patients' vocal functions are also described. This system is a useful tool for the treatment of laryngeal lesions causing dysphonia.     

Stereo‐ and Regioselective Direct Multi‐Deuterium‐Labeling Methods for Sugars

Deuterium‐labeled sugars can be utilized as powerful tools for the architectural analyses of high‐sugar‐containing molecules represented by the nucleic acids and glycoproteins, and chiral building blocks for the syntheses of new drug candidates (heavy drugs) due to their potential characteristics, such as simplifying the ¹H NMR spectra and the stability of C? D bonds compared with C? H bonds. We have established a direct and efficient synthetic method of deuterated sugars from non‐labeled sugars by using the heterogeneous Ru/C‐catalyzed H–D exchange reaction in D₂O under a hydrogen atmosphere with perfect chemo‐ and stereoselectivities. The direct H–D exchange reaction can selectively proceed on carbons adjacent to the free hydroxyl groups, and the deuterium labeling of various pyranosides (such as glucose and disaccharides), as well as furanosides, represented by ribose and deoxyribose was realized. Furthermore, the desired number of deuterium atoms can be freely incorporated into selected positions by the site‐selective protection of the hydroxyl groups using acetal‐type protective groups because the deuterium exchange reaction never proceeds on positions adjacent to the protected hydroxyl groups.     

Chemical-state analysis of organic semiconductors using soft X-ray absorption spectroscopy combined with first-principles calculation

The chemical states of organic semiconductors were investigated by total-electron-yield soft X-ray absorption spectroscopy (TEY-XAS) and first-principles calculations. The organic semiconductors, pentacene (C(22)H(14)) and pentacenequinone (C(22)H(12)O(2)), were subjected to TEY-XAS and the experimental spectra obtained were compared with the 1s core-level excited spectra of C and O atoms, calculated by a first-principles planewave pseudopotential method. Excellent agreement between the measured and the calculated spectra were obtained for both materials. Using this methodology, we examined the chemical states of the aged pentacene, and confirmed that both C-OH and C═O chemical bonds are generated by exposure to air. This result implies that not only oxygen but also humidity causes pentacene oxidation.     

Experimental Validation of Intermediate Termination in RAFT Polymerization with Dithiobenzoate via Comparison of Miniemulsion and Bulk Polymerization Rates

To understand if either of two controversial models for the retardation by RAFT agents is applicable, styrene polymerization using dithiobenzoate as the RAFT agent is carried out in both bulk and miniemulsion systems with the same rates of radical generation and the same RAFT agent concentrations. Miniemulsion polymerization with average diameters of the miniemulsion droplets of ≈107 nm is by far faster than in bulk, and the obtained rate of polymerization agrees well with the calculated results assuming a bimolecular termination between propagating radical and intermediate radical, generated by the addition reaction of propagating radical to the RAFT agent, which shows that the intermediate termination is the major reason for rate retardation by the RAFT agent.

     

Photo-triggered generation of a free thiol group on DNA: application to DNA conjugation

DNA oligomers possessing a 2-nitrobenzyl (NB) protected thiol group have been prepared. The photo-remove of the NB to generate a free thiol group in DNA has been analyzed by using reverse-phase HPLC and denaturing gel electrophoresis. The photo-triggered generation of the thiol function in DNA was applicable in the light-initiated ligation of thiol-modified DNA oligomers and Au–DNA conjugation.     

Sequential ruthenium-catalyzed hydroamination and rhenium-catalyzed C-H bond activation leading to indene derivatives

[reaction: see text] Formal [3 + 2] annulation of arylacetylenes and alpha,beta-unsaturated carbonyl compounds is achieved in a one-pot reaction by successive treatment of the acetylenes with aniline and a catalytic amount of Ru(3)(CO)(12) and NH(4)PF(6) and C-H bond activation catalyzed by [ReBr(CO)(3)(thf)](2). The result suggests that the second rhenium-catalyzed indene formation is not disturbed by the first catalyst system.