Improved synthesis of the polyhydroxylated central part of phoslactomycin B

A new approach to the C(7)-C(13) intermediate for the synthesis of phoslactomycin B was investigated. Asymmetric dihydroxylation of the β,γ-unsaturated ester proceeded cleanly to afford the β-hydroxyl-γ-lactone with 97.6% ee, which upon protection as the PMB ether followed by hydride reduction furnished a diol. After selective protection of the prim-OH, oxidation of the sec-OH and chelation-controlled addition of CH₂CHMgBr afforded the C(7)-C(11) segment. Later on, the C(11) stereocentre was constructed by the asymmetric transfer hydrogenation using the Noyori catalyst.     

Nitrogen-oxygen and oxygen-oxygen alkyl group migrations. synthesis of 1,2,4-triazine hydroxamic acid esters

Novel 1,2,4-triazine hydroxamic acid esters and alkylated 2, 3-dihydro-1,2,4-triazine N-oxides were prepared by rearrangement and selective alkylations of 3-alkoxy and 3-alkylamino-1,2,4-triazine N-oxides.     

Radical cation formation and crystal structure determination of 4′-dimethylamino-10-phenylpyrido[3,2-b]benzothiazine

The crystal structure of title compound, 4 , shows that the 10-aryl group is parallel to the plane bisecting the pyridobenzothiazine ring. This structure is in contrast to that normally found for phenothiazines substituted with electron-withdrawing substituents on the 10-phenyl ring. In those compounds, the 10-aryl group is perpendicular to the plane bisecting the phenothiazine ring. The esr spectrum of the cation radical of 4 shows that the radical is located on the hetero ring system which is opposite to that of the cation radical of 4′-dimethylamino-10-phenylphenothiazine in which the radical is located on the 10-aryl ring.     

High-performance liquid chromatographic assay of N(G)-monomethyl-L-arginine, N(G),N(G)-dimethyl-L-arginine, and N(G),N(G)'-dimethyl-L-arginine using 4-fluoro-7-nitro-2, 1,3-benzoxadiazole as a fluorescent reagent

N(G)-Monomethyl-L-arginine (L-NMMA), N(G),N(G)-dimethyl-L-arginine (ADMA), and N(G),N(G)'-dimethyl-L-arginine (SDMA) are emerging cardiovascular risk factors. A high-performance liquid chromatographic method with fluorescence detection for the simultaneous determination of L-NMMA, ADMA and SDMA is described. The assay employed 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) as a fluorescent derivatization reagent. After solid phase extraction with cation-exchange column, the methylated arginines were converted to fluorescent derivatives with NBD-F, and the derivatives were separated within 32 min on a reversed-phase column. Nomega-Propyl-L-arginine was Used as an internal standard. Extrapolated detection limits were 12 nM (12 fmol per injection) for L-NMMA and 20 nM (20 fmol per injection) for ADMA and SDMA, respectively, with a signal-to-noise ratio of 3. The calibration curves for L-NMMA, ADMA and SDMA were linear within the range of 50-5000 fmol. The method was applied to the quantitative determination of L-NMMA, ADMA and SDMA in 200 microl of rat plasma. The concentrations of L-NMMA, ADMA and SDMA in rat plasma were 0.16 +/- 0.03, 0.80 +/- 0.25 and 0.40 +/- 0.21 microM, respectively (n = 5).     

A Facile Synthesis of 3,4-Diamino-2,5-Diacylthieno[2,3-b]Thiophenes from Disodium(Dimercaptomethylene)Malononitrile and α-Halo Ketones

Various kinds of α-halo ketones readily reacted with disodium (dimercaptomethylene)malononitrile to give the corresponding 34-diamino-2,5-diacylthieno-[2,3-b]thiophenes in good to excellent yields. The reaction was successfully extended to the synthesis of a thienothiophene derivative having two sydnone rings by using the 4-(bromoacetyl)sydnone.     

Synthesis and crystal structure of 5-methyl-5,10-dihydrophenarsazine

The X-ray crystal structure of 5-methyl-5,10-dihydrophenarsazine, C₁₃H₁₂NAs, has been determined. The crystals are orthorhombic, space group P2₁2₁2₁, a = 8.511(4), b = 5.690(1), c = 23.535(9) Å, V = 1139.7(1.0)A³, and Z = 4. Least-squares refinement converged to R = 0.049 and Rw = 0.045. The central ring is in a boat conformation and the 5-methyl group is in the axial position with respect to the central ring. The folding angle between the planes of the two benzo rings is 154.1(4)°.     

Comparison of a new dead‐time correction method and conventional models for SIMS analysis

Recently, secondary ion mass spectrometry (SIMS) has been used in the analysis of not only impurities but also matrix elements, thus requiring a wide dynamic range for SIMS analysis. However, SIMS detectors, which are mostly used in pulse counting systems, have difficulties with detector saturation. In this paper, we investigate whether a dead‐time model that was developed for X‐ray measurement is applicable for SIMS analysis. We then compare a new correction method with conventional correction methods for detector saturation in SIMS analysis. We report that the new method can better correct the intensity in regions of higher intensity than that achieved by conventional methods. Copyright © 2012 John Wiley & Sons, Ltd.     

Ultrasonic effects on electroorganic processes. Part 14. Indirect electroreduction of benzyl chlorides with anthracene redox-mediatory system

Ultrasonic effects were observed in the indirect electroreduction of benzyl chlorides with a radical anion mediator electrogenerated from anthracene. Both the current efficiency for the toluenes formed and the current density (reaction rate) at a working electrode were significantly increased in potential-controlled electrolysis under ultrasonic irradiation (20 kHz). These effects are important from a practical aspect and are rationalized as being due to mass transport promotion caused by ultrasonic cavitation. Although the efficiency could be also increased in the direct electroreduction in the absence of the mediator under irradiation, the current density was only slightly increased.     

Evaluation of bone repair in the femur of rats submitted to laser therapy in different wavelengths: An image segmentation method of analysis

The aim of this study was to histologically assess the effect of laser therapy (LILT, 660 and 780 nm) on the repair of standardized bone defects on the femur of Wistar albinus rats. The sample was composed of 12 Wistar albinus young adult rats of both genders. Three randomized groups were studied: group I (control, n = 4), group II (LILT, 660 nm, n = 4), and group III (LILT, 780 nm, n = 4). Samples were prepared using a bone defect on the left-side femur surface of the animals, with a total dimension of approximately 3 mm³. Groups II and III were irradiated every 48 h from the second application, where the first dose was given immediately after surgery and the second application came 24 h after surgery. The irradiations were applied transcutaneously at four points around the wound for 14 days. At each point, a dose of 50 J/cm² (2 J) was given (s ～ 0.04 cm², 40 mW) and the total dose per session was 200 J/cm² (8 J). The sacrifices were made 15 days after surgery and the specimens were routinely processed to wax, serially cut, stained with an H&;E stain, and analyzed under light microscopy. The images were submitted to morphometric analysis using the image segmentation method using the K-means algorithm. The data obtained through the morphometric analysis were submitted to statistical analysis using the Tukey test. The results showed that the group treated with laser therapy in the infrared spectrum resulted in an increase in the repair of bone defects when compared with the group treated with the laser in the red spectrum and control group, which, in turn, had a very similar pattern of repair. A statistical significance (p < 0.01) was observed when comparing the results of group III and the results of Groups I and II. We concluded that the LILT in the infrared spectrum produced a positive biomodulation effect on the repair of bone defects in the femur of rats.     

Evaluating glycogen signal contamination in muscle by (13)C MRS of the liver

To evaluate the contamination of glycogen signal synthesized in skeletal muscle by that in the liver, long-term monitoring of over 7 h of in vivo [1-¹³C] glycogen synthesis/degradation at the right abdomen and left shoulder was achieved using a 3.0-T clinical MR system. ¹³C MR spectra without localization were obtained from five healthy volunteers before and after oral administration of 85 g of d-glucose, including 10 g of 99% [1-¹³C] glucose. In all volunteers, the relative signal intensities at the abdomen to those at shoulder were about two- to fivefold, and those of time-course changes at the abdomen and shoulder were dissimilar. It is considered that the quantity of muscle-synthesized glycogen signal at the abdomen is less than that at the shoulder because of the lesser muscle volume at the abdomen, and it may be less affected for evaluating glycogen synthesis/degradation in the liver even without localization pulses.