Visible-Light-Induced Synthesis of 1,2,3,4-Tetrahydroquinolines through Formal [4+2] Cycloaddition of Acyclic α,β-Unsaturated Amides and Imides with N,N-Dialkylanilines

1,2,3,4-Tetrahydroquinolines should be applicable to the development of new pharmaceutical agents. A facile synthesis of 1,2,3,4-tetrahydroquinolines that is achieved by a photoinduced formal [4+2] cycloaddition reaction of acyclic α,β-unsaturated amides and imides with N,N-dialkylanilines under visible-light irradiation, in which a new Ir^III complex photosensitizer, a thiourea, and an oxidant act cooperatively in promoting the reaction, is reported. The photoreaction enables the synthesis of a wide variety of 1,2,3,4-tetrahydroquinolines, while controlling the trans/cis diastereoselectivity (>99:1) and constructing contiguous stereogenic centers. A chemoselective cleavage of an acyclic imide auxiliary is demonstrated.     

Synthesis of pyrylium salts from trisubstituted 1,4-pentadiyn-3-ols with HClO4

The synthesis of 2,4,6-trisubstituted pyrylium salts from 1,3,5-trisubstituted 1,4-pentadiyn-3-ols with HClO₄ is reported for the first time.     

Energy Transport in Weakly Anharmonic Chains

We investigate the energy transport in a one-dimensional lattice of oscillators with a harmonic nearest neighbor coupling and a harmonic plus quartic on-site potential. As numerically observed for particular coupling parameters before, and confirmed by our study, such chains satisfy Fourier’s law: a chain of length N coupled to thermal reservoirs at both ends has an average steady state energy current proportional to 1/N. On the theoretical level we employ the Peierls transport equation for phonons and note that beyond a mere exchange of labels it admits nondegenerate phonon collisions. These collisions are responsible for a finite heat conductivity. The predictions of kinetic theory are compared with molecular dynamics simulations. In the range of weak anharmonicity, respectively low temperatures, reasonable agreement is observed.     

Applications of a photoion-photoion-coincidence technique to the study of photon-stimulated ion-desorption process following K-shell excitation

We have investigated the photon-stimulated ion-desorption from deuterated formic acid (DCOOD) monolayer chemisorbed on Si(100) crystal by applying a photoion-photoion-coincidence technique. The true-coincidence yields of an ion pair C⁺---D⁺ are given in the photon energy range (275–400 eV) above the C 1s absorption edge. The partial ion yields and Auger electron yields re presented for comparison. It was found that the multielectron (shake-off) excitation promotes the multiple bond-breaking of the adsorbate and the ion pair C⁺–D⁺ desorption events.     

Fluorescence labeling method for aryl halides with 4-(4,5-diphenyl-1H-imidazol-2-yl)phenylboronic acid based on Suzuki coupling reaction

For the first time, fluorescence labeling methods for aryl halides with a fluorescent arylboronic acid was developed on the basis of a Suzuki coupling reaction. 4-(4,5-diphenyl-lH-imidazol-2-yl)phenylboronic acid (DPA) was used as a fluorescence labeling reagent. In order to explore its analytical performance, the reaction conditions were optimized using simple bromobenzene derivatives. The reactivity was then investigated with chloro- and iodobenzene derivatives, and also bromobenzene derivatives with different position of substituents. The order of reactivity with DPA: iodobenzene > bromobenzene more more than chlorobenzene derivatives, and p- > m- > o-substituted bromobenzenes. The detection limits of bromobenzene, 4-bromotoluene, and 4-bromoanisole ranged from 0.2 to 1.4 pmol/injection at a signal-to-noise ratio, (S/N) of 3. The applicability of the method to biological samples was also evaluated using clofibrate as the analyte. The reaction was found not only to proceed well but also to be selective for clofibrate even in the presence of plasma components. The method allowed the sensitive detection of clofibrate in human plasma with the detection limit of 170 pmol/mL (260 fmol/injection) at a S/N = 3. The proposed method is highly selective and sensitive and thus would be useful for labeling of aryl halides that do not have other functional groups that could be labeled by currently available fluorescent labeling reagents.     

The Irreducible Modules of the Terwilliger Algebras of Doob Schemes

Let Y be any commutative association scheme and we fix any vertex x of Y. Terwilleger introduced a non-commutative, associative, and semi-simple C-algebraT=T(x) for Y and x in [4]. We call T the Terwilliger (or subconstituent) algebra ofY with respect to x.Let be an irreducible T(x)-module. W is said to be thin if W satisfies a certain simple condition.Y is said to be thin with respect to x if each irreducible T(x) -module is thin. Y is said to be thin if Y is thin with respect to each vertex in X.The Doob schemes are direct product of a number of Shrikhande graphs and some complete graphsK ₄ . Terwilliger proved in [4] that Doob scheme is not thin if the diameter is greater than two. I give the irreducible T(x)-modules of Doob schemes.     

The first total synthesis of (+/-)-arisugacin A, a potent, orally bioavailable inhibitor of acetylcholinesterase

The first convergent total synthesis of (+/-)-arisugacin A was accomplished by stereoselective construction of the arisugacin skeleton via a Knoevenagel-type reaction of an alpha,beta-unsaturated aldehyde with a 4-hydroxy 2-pyrone and stereoselective dihydroxylation followed by deoxygenation.     

Stepwise gradient of buffer concentration for capillary electrochromatography of peptides on sulfonated naphthalimido-modified silyl silica gel

The advantage of using a stepwise gradient of buffer concentration in CEC was demonstrated with the mixed-mode stationary phase, 3-(4-sulfo-1,8-naphthalimido)propyl-modified silyl silica gel (SNAIP). Before the application of a stepwise gradient, the effect of buffer concentration on the separations of six peptides and tryptic digests was investigated. Bubble formation caused by Joule heating at currents up to 95 microA was successfully suppressed by using SNAIP column even without pressurization, which contributed to a stepwise gradient of buffer concentration. Utilizing the stepwise gradient improved and shortened the separation of six peptides as compared to the separation under an isocratic elution.     

Field survey of Glycyrrhiza plants in Central Asia (3). Chemical characterization of G. glabra collected in Uzbekistan

The chemical characteristics of Glycyrrhiza glabra L. were investigated at a habitat in Uzbekistan. HPLC analysis of the underground parts indicated that glycyrrhizin contents varied from 3.3 to 6.1% of dry weight, and that glabridin, a species-specific flavonoid for G. glabra, was detected in all underground samples (0.08-0.35% of dry weight). HPLC analysis of the leaves indicated that G. glabra plants collected in the present study could be divided into two types, RT-type and IQ-type, according to their major flavonol glycosides, rutin or isoquercitrin, respectively.     

Determination of bisphenol A in rat brain by microdialysis and column switching high-performance liquid chromatography with fluorescence detection

A sensitive column switching HPLC-fluorescence detection for determination of bisphenol A (BPA) in rat brain by coupling with microdialysis was developed. A microdialysis probe was inserted into the hypothalamus of rat brain and an artificial cerebrospinal fluid was used for perfusion. BPA in brain dialysate was subjected to a fluorescent derivatization with 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride (DIB-Cl), and the excess reagent was removed by a column-switching technique. Separation was carried out on two ODS semimicro-columns with the mobile phase of acetonitrile-H(2)O-methanol-tetrahydrofuran (55:10:35:2.5, v/v) and acetonitrile-0.1 M acetate buffer (pH 3.0)-methanol (35:10:55, v/v) at a flow rate of 0.10 and 0.15 mL/min for a precolumn and a separation column, respectively. Fluorescence intensity was monitored at 475 nm with excitation of 350 nm. BPA could be sensitively detected at 0.3 ppb in 60 micro L brain microdialysate at a signal-to-noise ratio of 3. By the proposed method, concentrations of BPA in rat brain and plasma were monitored for 8 h after single i.v. or oral administration. It is proved that BPA is capable of penetrating the blood-brain barrier. The ratio of the area under the concentration-time curve of BPA in rat brain to that in blood was estimated to be about 3.0-3.8%.