Studies on antitumor agents. IX. Synthesis of 3'-O-benzyl-2'-deoxy-5-trifluoromethyluridine

A practical synthesis of 3'-O-benzyl-2'-deoxy-5-trifluoromethyluridine (1), a candidate antitumor agent for clinical testing, was developed from 2'-deoxy-5-iodouridine (3). Benzylation of 2'-deoxy-5-iodo-5'-O-trityluridine (14) with benzyl bromide and sodium hydride in tetrahydrofuran gave the 3'-O-derivative (16). Benzoylation of 16 afforded the N3-benzoyl derivative (17). Coupling of 17 with trifluoromethylcopper, prepared from bromotrifluoromethane and copper powder in the presence of 4-dimethylaminopyridine, gave the 5-trifluoromethyl derivative (19) minimally contaminated with the 5-pentafluoroethyl compound. Deprotection of 19 furnished 1.     

Surface-potential reversibility of an amino-terminated self-assembled monolayer based on nanoprobe chemistry

Nanoprobe chemistry offers a promising approach for the construction of nanostructures consisting of organic molecules by employing the tip of a scanning probe microscope. In a previous report, we demonstrated that a nitroso-terminated surface on an organosilane self-assembled monolayer could be converted into an amino-terminated surface by applying such a nanoprobe electrochemical technique. This paper reports on surface-potential reversibility originating from a reversible chemical reaction between amino and nitroso groups. In addition, we demonstrate surface-potential memory based on this chemical reversibility. Amino-terminated SAMs were prepared from p-aminophenyl-trimethoxysilane through chemical vapor deposition. Surface potentials were acquired by Kelvin force microscopy. When scanning probe lithography was conducted with a gold tip at positive-bias voltages, the surface potential of the scanned area shifted dramatically in the negative direction. Scanning with negative-bias voltages led to positive shift in the surface potential of the scanned area. The surface potential could be recovered even after multiple scannings with positive and negative applied bias voltages. On the basis of this discovery, we also succeeded in demonstrating surface-potential memory via our nanoprobe electrochemical technique.     

Absorption enhancement of polypeptide drugs by cyclodextrins. I. Enhanced rectal absorption of insulin from hollow-type suppositories containing insulin and cyclodextrins in rabbits.

The absorption of insulin (from porcine pancreas) from the rectum of rabbits after the administration of hollow-type suppositories containing insulin and five kinds of cyclodextrins (CyDs) was investigated. Three types of suppositories were employed: suppository I containing insulin (approximately 26 IU/mg) and various amounts of each CyD in citric buffer solution at pH 3.0 or powder in its cavity, suppository II containing CyD without insulin, and suppository III containing insulin without CyD. Without CyD, the insulin and glucose levels in plasma were unchanged, whereas a significant increase in the plasma insulin concentration and a marked decrease in the glucose levels were found following simultaneous administration of insulin and CyDs by suppository I. The enhancing effect of CyD on rectal insulin absorption (absorption-enhancing effect) by chemically modified CyDs (heptakis(2,6-di-O-methyl)-beta-CyD (DM-beta-CyD) and 2-hydroxypropyl-beta-CyD (HP-beta-CyD)) was higher than those by natural CyDs (alpha-, beta-, and gamma-CyD). The area under the plasma concentration-time curve (AUC) and Cmax of insulin significantly decreased with the preadministration (administration of CyD 6, 24 and 48 h before rectal insulin administration) of DM-beta-CyD. The absorption-enhancing effect disappeared 24 h after preadministration. These results suggest that CyDs enhance insulin absorption from the rectum, and that attenuation of the membrane transport barrier function in the rectum recovers at a maximum of 24 h after administration of CyDs.     

Generation of alkoxycarbenium ion pools from thioacetals and applications to glycosylation chemistry

[reaction: see text] Alkoxycarbenium ions have been generated and accumulated as "cation pools" by the low-temperature electrochemical oxidation of alpha-phenylthioethers. Although an unsuccessful attempt to accumulate glycosyl cations was made, a one-pot method for electrochemical glycosylation, which involves anodic oxidation of thioglycosides to generate glycosyl cation equivalents followed by their reactions with glycosyl acceptors, has been developed.     

Synthesis and spectroscopic analysis of tetraphenylporphyrinatoantimony(V) complexes linked to boron-dipyrrin chromophore on axial ligands

Tetraphenylporphyrinatoantimony(V) complexes, linked to boron-dipyrrin chromophores on axial ligands, were synthesized. The fluorescence spectra of 1a, 1b and 1c (3-[4-(N,N′-difluorobornyl-5-dipyrrinyl)phenyl]propoxo(methoxo)antimony(V) tetraphenylporphyrin bromide (1a); 6-[4-(N,N′-difluorobornyl-5-dipyrrinyl)phenyl]hexyloxo(methoxo)antimony(V) tetraphenylporphyrin bromide (1b); bis{3-[4-(N,N′-difluorobornyl-5-dipyrrinyl)phenyl]propoxo}antimony(V) tetraphenylporphyrin bromide (1c)) were analyzed under the excitations of N,N′-difluorobornyl-5-dipyrrinylphenyl (Bdpy) and tetraphenylporphyrinatoantimony(V) (Sb(TPP)) chromophores. Under the irradiation of Bdpy chromophore, the excitation energy was transferred from Bdpy chromophore to the Sb(TPP) moiety at 0.13–0.40 of the quantum yields, even in a polar solvent. On the other hand, the emission of Sb(TPP) chromophores was quenched by Bdpy chromophores at rate constants of 10⁸–10⁹ s⁻¹, independent of on the solvent polarity. Under the excitation of the Bdpy chromophore of 1d (3-[4-(N,N′-difluorobornyl-5-dipyrrinyl)phenyl]propoxo(phenyloxo)antimony(V) tetraphenylporphyrin bromide) involving both the Bdpy and the phenoxy chromophores on the axial ligands, the excited singlet state of the Sb(TPP) chromophore generated by the energy transfer from the Bdpy chromophore was quenched by the phenoxy ligand via non-radiative processes involving electron transfer. However, rapid back electron-transfer may occur because no absorption of the anion radical of Sb(TPP) was observed by nanosecond laser photolysis.     

Purification of Food Color Red No. 106 (acid red) using pH-zone-refining counter-current chromatography

pH-Zone-refining counter-current chromatography was successfully applied to the separation of the main components of Food Color Red No. 106 (R-106, acid red, Color Index No. 45100). A 300-mg quantity of sample was separated using the following two-phase solvent system: n-butanol-water, 40 mM sulfuric acid in organic stationary phase and 30 mM ammonia in aqueous mobile phase. The obtained fractions were analyzed by high-performance liquid chromatography and fast atom bombardment mass spectrometry. The separation yielded 261.9 mg of main component of acid red with purity of 99.9%.     

A mixed version of Menger's theorem

An(a, b)-n-fan means a union ofn internally disjoint paths. Menger's theorem states that a graphG has an(a, b)-n-fan if and only ifG isn-connected betweena andb. We show thatG contains edge-disjoint(a, b)-n-fans if and only if for anyk withk0min{n–1, |V(G)|–2} and for any subsetX ofV(G)-{a, b} with cardinalityk, G-X is (n-k)-edge-connected betweena andb.     

Lipid-soluble and water-soluble arsenic compounds in blubber of ringed seal (Pusa hispida)

High concentrations of arsenic were observed in the blubber of ringed seals (Pusa hispida) in our previous study. To better understand the arsenic accumulation in blubber of marine mammals, arsenicals in the blubber of ringed seal were characterized using high performance liquid chromatography–inductively coupled plasma mass spectrometry (HPLC–ICPMS). The most predominant water-soluble arsenical in the blubber was dimethylarsinic acid (DMA), in spite of the predominance of arsenobetaine in other tissues. Lipid-soluble fraction was hydrolyzed under mild (tetraethylammonium hydroxide (TEAH) hydrolysis) and strong (NaOH hydrolysis) conditions, and then an aliquot of hydrolysate was injected onto HPLC–ICPMS. Both TEAH-labile and TEAH-stable/NaOH-labile lipid-soluble fractions contained precursors of DMA. These results suggest that the blubber might be the pool of DMA and DMA-containing precursors in ringed seals.     

Immunoactivity of polymer microspheres with their hydrophilic/hydrophobic heterogeneous surface sensitized with an antibody

Styrene/2-hydroxyethyl methacrylate polymer microspheres consisting of various polymer compositions were produced by emulsifier-free seeded emulsion polymerization technique. Using these microspheres, which should have hydrophilic/hydrophobic heterogeneous surface, the effects of surface hydrophilicity on the main, fundamental requirements for an immunomicrosphere — high colloidal stability, sensitive immunologic agglutinability and insensitive non-specific agglutinability — were studied in detail. There was a region of the surface hydrophilicity that satisfied the three requirements simultaneously.Part CII of the series Studies on Suspension and Emulsion.