Highly beta-selective O-glucosidation due to the restricted twist-boat conformation

[reaction: see text] Ethyl 1-thio-2,3,4,6-tetrakis-O-triisopropylsilyl-beta-d-glucopyranoside, ethyl 6-O-benzyl-1-thio-2,3,4-tris-O-triisopropylsilyl-beta-d-glucopyranoside, and ethyl 6-O-pivaloyl-1-thio-2,3,4-tris-O-triisopropylsilyl-beta-d-glucopyranoside induced highly beta-selective O-glucosidations. Among them, the 6-O-pivaloylated substrate provided the best selectivity up to alpha/beta = 3:97 with cyclohexylmethanol, and the substrate was used for glucosidations with secondary and tertiary alcohols in a highly beta-selective manner. The selectivity would be caused by the twist-boat conformation of the pyranose; this is the first beta-selective O-glucosidation based on conformational control of the pyranose ring.     

Determination of topotecan in human and mouse plasma and in mouse tissue homogenates by reversed-phase high-performance liquid chromatography

A sensitive and selective reversed-phase high-performance liquid chromatographic (HPLC) assay has been developed and validated for quantification of total topotecan in human and mouse plasma and in mouse tissue samples. Isocratic separation was achieved on a Zorbax SB-C(18) column and topotecan was monitored fluorimetrically. Two ranges of calibrations curves were used to determine lower levels of topotecan more accurately. Acceptable accuracy and precision was achieved for all matrices. Topotecan was stable upon repeated freeze-thawing for three cycles or storage for 24 h at ambient temperatures in spiked plasma samples and tissue homogenates, except in heart homogenates. In an additional validation experiment in which (14)C-labeled topotecan was administered to mice, the levels of unchanged topotecan were about 80-90% of the total radioactivity in tissue homogenates collected 10 min after drug administration and virtually similar as in plasma samples. However, results in tissue homogenates obtained 4 h post-drug administration indicated substantial metabolism of topotecan. This assay is suitable for studying the pharmacokinetics and tissue distribution of topotecan in mice. Our results demonstrate the importance of including all tissues of interest for pharmacokinetic studies in the validation procedure.     

Analysis of mural paintings in Istria

Fragments of wall paintings from Istria, coming from the Basilica of Guran near Vodnjan, from the cemeterial Church of Saint Simeon in Guran and from the Benedictine monastery of Santa Maria Alta near Bale were studied. The analytical instrumental techniques used were Optical Microscopy, Scanning Electron Microscopy equipped with an EDS microanalysis detector, X Ray diffraction, FTIR infrared Spectroscopy and Raman Spectroscopy. Red and yellow pigments used in Guran and Bale have bean derived from red and yellow istrian bauxites, as already demonstrated for works from 11th to 15th century. The blue pigment found in the paintings of the Bale Chapel is a lapislazzuli blue; this fact confirms the literature data referring to the period from 11th to the 16th century. The materials and pigments used at Bale and Guran fit with the Istrian tradition and history of painting going back to the first Carolingian period.     

Synthesis of 4-alkoxy-8-hydroxyquinolines

Quinolines with a hydroxyl group at the 8-position and an alkoxy group at the 4-position are rare compounds. In this paper the synthesis of five 4-alkoxy-8-hydroxyquinolines is reported. The key reaction in the synthetic route is a selective protection of the hydroxyl group at C-atom 8 in 4,8-dihydroxyquinoline with a tosyl group and the hydrolytic removal of the protective group after the alkylation. The tosyl group is stable during the alkylations with various alkylating agents in the presence of sodium hydride.     

Experimental and Theoretical DFT Investigations in the [2,3]-Wittig-Type Rearrangement of Propargyl/Allyl-Oxy-Pyrazolones

Here we report the synthesis of interesting 3-alkyl-4-hydroxy-1-aryl-4-(propa-1,2-dienyl)1H-pyrazol-5(4H)-ones and 9-alkyl-7-aryl-1-oxa-7,8-diazaspiro[4.4]nona-3,8-dien-6-ones, starting from 1,2-diaza-1,3-dienes (DDs) and propargyl alcohol. The reaction proceeds through a sequence Michael-type nucleophilic attack/cyclization/[2,3]-Wittig rearrangement. In the same way, the reaction between the aforementioned DDs and allyl alcohol furnished 4-allyl-4-hydroxy-3-alkyl-1-aryl-1H-pyrazol-5(4H)-ones. A DFT study was also carried out, in order to have decisive clarifications about the mechanism.     

In vivo imaging of cell morphology and cellular processes in Caenorhabditis elegans, using non-linear phenomena

We present the detailed imaging of structures and processes of the nematode Caenorhabditis elegans (C. elegans) using non-linear microscopy. Complementary information about the anatomy of the nematode was collected by implementing a combination of two photon excitation fluorescence (TPEF), second and third harmonic generation (SHG and THG) image contrast modes on the same microscope. Three-dimensional (3D) reconstructions of TPEF, SHG and THG images were also performed. Moreover, THG imaging technique has been tested as a potential, novel, non-destructive diagnostic tool for monitoring cellular processes in vivo, such as neuronal degeneration.     

Tissue-specific and neural activity-regulated expression of human BDNF gene in BAC transgenic mice

Background  

Brain-derived neurotrophic factor (BDNF) is a small secreted protein that has important roles in the developing and adult nervous system. Altered expression or changes in the regulation of the BDNF gene have been implicated in a variety of human nervous system disorders. Although regulation of the rodent BDNF gene has been extensively investigated, in vivo studies regarding the human BDNF gene are largely limited to postmortem analysis. Bacterial artificial chromosome (BAC) transgenic mice harboring the human BDNF gene and its regulatory flanking sequences constitute a useful tool for studying human BDNF gene regulation and for identification of therapeutic compounds modulating BDNF expression.