Fluorescent behavior of 2‐(3,4,5,6‐tetrafluoro‐2‐hydroxyphenyl)imidazo‐[1,2‐a]pyridine in the presence of metal perchlorate

2‐(3,4,5,6‐Tetrafluoro‐2‐hydroxyphenyl)imidazo[1,2‐a]pyridine ( 1 ) emits long wavelength light around 540 nm both in polar and in nonpolar solvents. Zn²⁺ perchlorate in acetonitrile causes the intermediate wavelength emission around 430 nm, which is ascribed to the species where the imidazole nitrogen atom and the phenolate oxygen atom bridge Zn²⁺. In the presence of Hg²⁺ and Al³⁺ perchlorates, short wavelength emission around 370 nm is strongly increased and this fluorescent enhancement is attributable not to the coordination of Hg²⁺ and Al³⁺ to 1 but to the formation of the salt of perchloric acid of 1 .     

Amphidinolides T2, T3, and T4, new 19-membered macrolides from the dinoflagellate Amphidinium sp. and the biosynthesis of amphidinolide T1.

Three new 19-membered macrolides, amphidinolides T2 (2), T3 (3), and T4 (4), structurally related to amphidinolide T1 (1) have been isolated from two strains of marine dinoflagellates of the genus Amphidinium. The structures of 2-4 were elucidated on the basis of spectroscopic data. The absolute configurations at C-7, C-8, and C-10 of 1-4 were determined by comparison of NMR data of their C-1-C-12 segments with those of synthetic model compounds for the tetrahydrofuran portion. The biosynthetic origins of amphidinolide T1 (1) were investigated on the basis of 13C NMR data of a 13C enriched sample obtained by feeding experiments with [1-(13)C], [2-(13)C], and [1,2-(13)C2] sodium acetates and 13C-labeled sodium bicarbonate in the cultures of the dinoflagellate. These incorporation patterns suggested that amphidinolide T1 (1) was generated from four successive polyketide chains, an isolated C1 unit formed from C-2 of acetates, and three unusual C2 units derived only from C-2 of acetates. Furthermore, it is noted that five oxygenated carbons of C-1, C-7, C-12, C-13, and C-18 were not derived from the C-1 carbonyl, but from the C-2 methyl of acetates.     

Biosynthetic study of amphidinolide B

The biosynthetic origins of amphidinoide B (1) were investigated on the basis of 13C-NMR data of 13C-enriched samples obtained by feeding experiments with [1-(13)C], [2-(13)C], and [1,2-(13)C2] sodium acetates in cultures of a dinoflagellate Amphidinium sp. These incorporation patterns suggested that 1 was generated from three successive polyketide chains, an isolated C1 unit from C-2 of acetates, six branched C1 units from C-2 of acetates, and an "m-m" and an "m-m-m" unit derived only from C-2 of acetates. The labeling patterns of amphidinolide B (1) were different from those of amphidinolide H (2), a 26-membered macrolide closely related to 1.     

Absolute stereochemistry of amphidinolide C

[structure in text] The absolute configurations at 12 chiral centers in amphidinolide C (1), a potent cytotoxic 25-membered macrolide isolated from a marine dinoflagellate Amphidinium sp., were determined to be 3S, 4R, 6R, 7R, 8R, 12R, 13S, 16S, 20R, 23R, 24R, and 29S by combination of NMR analyses, degradation experiments, and synthesis of the C-1-C-7 segment.     

Desymmetric hydrogenation of a meso-cyclic acid anhydride toward biotin synthesis

Catalytic reactivity in the hydrogenation of a cyclic anhydride to a biotin synthetic intermediate has been investigated on the basis of Lyons’ original method using Wilkinson Ru complex, revealing the high performance of DPPF and XANTPHOS diphosphines possessing wide bite angles. The results have shown a new trail for design of the corresponding asymmetric catalysts, and the potential utility of (S,S)-Et-FerroTANE and (S,S)-(R,R)-Ph-TRAP has been demonstrated.     

Electrodeposition of aluminum–hafnium alloy from the Lewis acidic aluminum chloride-1-ethyl-3-methylimidazolium chloride molten salt

The electrochemistry of Hf(IV) and the electrodeposition of Al–Hf alloys were examined in the Lewis acidic 66.7–33.3 mol% aluminum chloride-1-ethyl-3-methylimidazolium chloride molten salt containing HfCl₄. When cyclic staircase voltammetry was carried out at a platinum disk electrode in this melt, the deposition and stripping waves for Al shifted to negative and positive potentials, respectively, suggesting that aluminum stripping is more difficult due to the formation of Al–Hf alloys. Al–Hf alloy electrodeposits containing ~13 at.% Hf were obtained on Cu rotating wire and cylinder electrodes. The Hf content in the Al–Hf alloy deposits depended on the HfCl₄ concentration in the melt, the electrodeposition temperature, and the applied current density. The deposits were composed of dense crystals and were completely chloride-free. The chloride-induced pitting corrosion potential of the resulting Al–Hf alloys was approximately +0.30 V against pure aluminum when the Hf content was above 10 at.%.     

Dioxopyrrolines. LXII. Diels-Alder reaction of 1-Aryl-4- and 5-methoxycarbonyl-1H-pyrrole-2,3-diones with various 1,3-dienes

Two new dioxopyrrolines (1-aryl-4-methoxycarbonyl-1H-pyrrole-2,3-dione 6 and the 5-methoxycarbonyl isomer 8) behaved as good dienophiles to some kind of 1,3-dienes examined. In most cases, the products were explained by the reaction where the largest lobe of HOMO of dienes reacted to the larger LUMO of dienophiles in an expected cis-endo manner. However, in the reactions of 8 with alkylbutadienes, piperylene and isoprene, abnormality in the reaction was observed, which was well explained by taking account of steric factors.     

Use of the MALDI BioTyper system with MALDI–TOF mass spectrometry for rapid identification of microorganisms

In a clinical diagnosis microbiology laboratory, the current method of identifying bacterial isolates is based mainly on phenotypic characteristics, for example growth pattern on different media, colony morphology, Gram stain, and various biochemical reactions. These techniques collectively enable great accuracy in identifying most bacterial isolates, but are costly and time-consuming. In our clinical microbiology laboratory, we prospectively assessed the ability of matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI–TOF MS) to identify bacterial strains that were routinely isolated from clinical samples. Bacterial colonies obtained from a total of 468 strains of 92 bacterial species isolated at the Department of Clinical Laboratory at Chiba University were directly placed on target MALDI plates followed by addition of CHCA matrix solution. The plates were then subjected to MALDI–TOF MS measurement and the microorganisms were identified by pattern matching with the libraries in the BioTyper 2.0 software. Identification success at the species and genus levels was 91.7% (429/468) and 97.0% (454/468), respectively. MALDI–TOF MS is a rapid, simple, and high-throughput proteomic technique for identification of a variety of bacterial species. Because colony-to-colony differences and effects of culture duration on the results are minimal, it can be implemented in a conventional laboratory setting. Although for some pathogens, preanalytical processes should be refined, and the current database should be improved to obtain more accurate results, the MALDI–TOF MS based method performs, in general, as well as conventional methods and is a promising technology in clinical laboratories.