Formation of Azulenequinone Derivatives from Variously Functionalized Azulenes by Bromine-oxidation

Variously functionalized 1,5- and 1,7-azulenequinones were easily derived in one-pot in 30-50% yield from the bromine-oxidation of 2-methoxyazulene and 2-methyl derivatives of 1-cyano-, 1-methoxycarbonyl- and its 7-isopropyl derivatives, while 1-methoxycarbonylazulene afforded several unstable products from which we could not isolate any azulenequinones. 1-Acetylazulene afforded 3-bromo-1,5- and -1,7-azulenequinones via side-chain brominated intermediates in high yield. 1,3-Dichloroazulene afforded a mixture of 3-chloro-1,5- and −1,7-azulenequinones, while 1-fluoro- and 1,3-diiodoazulene gave a mixture of 3-bromoazulenequinones. Analogous oxidation of 1,3-difluoroazulene produced 3-fluoroazulenequinones, but we could not isolate them due to its instability. Hydroxy group of 2-(3-hydroxypropyl)azulene was intact during this quinone formation reaction.     

An Electrically-Heated furnace for organic elementary analysis

Summary A stationary furnace of split type and an stationary automatic combustion furnace for organi elementary analysis have been designed. They are similar in construction. Having rapid-heating and rapid-cooling characteristics and satisfactory uniformity of temperature over the whole length, they are very convenient to use for combustion analysis.

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Zusammenfassung Ein aufklappbarer und ein automatischer Verbrennungsofen für die organische Elementaranalyse werden beschrieben. Sie sind einander in der Konstruktion ähnlich und lassen sich rasch anheizen und abkühlen. Die Temperatur ist über die ganze Länge gleichmäßig verteilt. Die Öfen eignen sich sehr gut für Verbrennungsanalysen.

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Résumé On a réalisé un four fixe de type « à fente» et un four fixe à combustion automatique pour l'analyse élémentaire organique. Ils sont de construction identique. Ils conviennent très bien pour l'analyse par combustion en raison de leurs caractéristiques de chauffe rapide et de refroidissement rapide et de l'obtention satisfaisante d'une température uniforme sur toute la longueur.

     

Synthesis and spectral properties of a highly soluble push-pull type of quinoidal thiophenes

[structures: see text] A series of push-pull quinoidal thiophenes 5a,b and 6a-c substituted with an electron-donating 1,3-dithiol-2-ylidene unit and an electron-withdrawing dicyanomethylene unit at the terminals is developed. They are highly soluble in common solvents and deeply colored with extension of the thienoquinoid skeleton.     

Preparation and metal-adsorption properties of polystyrene resins functionalized with multidentate ligands having nitrogen and sulfur donor sets

N-Mercaptoethylated derivatives of macroporous polystyrene resins functionalized with diethylenetriamine or pyridylamines have been synthesized. The resin with higher sulfur content reveals better selectivity toward ‘soft’ metal ions. Concentration of Ag(I) and Hg(II) has been examined by the column containing the present chelating resins.     

Synthesis and antibacterial activities of novel oxazine and thiazine ring-fused tricyclic quinolonecarboxylic acids: 10-(Alicyclic amino)-9-fluoro-7-oxo-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acids and the corresponding 1-thia congeners

Several analogs 4 and 5 of Ofloxacin ( 1 ) which contain the oxazine and thiazine rings fused with a quinolone carboxylic acid moiety, respectively, were prepared and their in vitro and in vivo antibacterial activities were compared with those of 1 and its previously prepared 3-exo-methylene analogs 2 and 3 . Unlike 1, 2 , and 3 , analogs 4 and 5 possess an antiaromatic oxazine and thiazine moiety and show markedly lower antibacterial activities. Alteration of their C-10 amino-substituent groups from piperazine to azetidine significantly improved the in vitro antibacterial activities, particularly in the case of the thiazine derivative 5 , but not the in vivo ones. The antibacterial activities of these three types of tricyclic quinolonecarboxylic acids are briefly discussed on the basis of the molecular properties revealed by molecular orbital calculation. The molecular dipole moment was suggested to be one possible factor controlling the binding affinity of these compounds with DNA gyrase.     

Reduction of carbonyl compounds via hydrosilylation: V. Synthesis of optically active allylic alcohols via regioselective asymmetric hydrosilylation

Regioselective asymmetric reduction of prochiral α,β-unsaturated ketones to optically active allylic alcohols was performed via hydrosilylation catalyzed by a rhodium(I) complex with (+)-BMPP, (+)-DIOP and (?)-DIOP as chiral ligands. The allylic alcohols with optical purity up to 69% e.e. were obtained in good yields. The extent of asymmetric induction was found to depend on the stereo-electronic matching of the chiral ligand, ketone and hydrosilane employed. In the asymmetric reduction of (R)-carvone, leading to carveol, the extent of asymmetric induction was found to depend markedly on the ligand/rhodium ratio. Either trans-(5R,1S)-carveol or cis-(5R,1R)-carveol was obtained with good stereoselectivity by using (?)-DIOP or (+)-DIOP as chiral ligand, and it turned out that the chiral center present in carvone had only a slight influence on the asymmetric induction by the chiral catalysts.     

Synthesis of acyclic nucleotide analogues possessing a difluoromethylene phosphonyl group at the side chain

A synthetic approach to a new type of acyclic nucleotide analogues 8 and 9 was examined. The design was based on acyclic modification of MRS 2179, a P2Y₁-antagonist, and replacement of one of two phosphate groups characterized by MRS 2179 with an isosteric difluoromethylenephosphonyl group. The nucleotide analogues 8 and 9 were enantio-divergently prepared as their ester-protecting derivatives from a highly differentiated 1,5-pentanediol derivative possessing a difluoromethylenephosphonyl group at the 3-position.     

Asymmetric electrochemical lactonization of diols on a chiral 1-azaspiro[5.5]undecane N-oxyl radical mediator-modified graphite felt electrode

A graphite felt electrode modified with (6S,7R,10R)-4-amino-2,2,7-trimethyl-10-isopropyl-1-azaspiro[5.5]undecane N-oxyl was prepared for electrocatalytic oxidation of diols; electrolysis of diols on the modified electrode yielded optically active lactones (92.0-96.4%), with an enantiopurity of 82-99% ee.     

Structure and structural changes of the silk fibroin from Samia cynthia ricini using nuclear magnetic resonance spectroscopy

The structure of silk fibroin from a wild silkworm, S. c. ricini, the amino acid sequence of which consists of repeated poly-Ala and Gly-rich regions, was examined by using solution and solid-state NMR methods. The structural transition of the silk fibroin in aqueous solution was monitored by using 13C solution NMR spectroscopy as a function of temperature. The fast exchange with respect to the chemical shift between the helix and coil conformations was observed in the poly-Ala region and the slow conformational change from alpha-helix to random coil was observed for the Gly residue adjacent to the N-terminal Ala residue of the poly-Ala region. The torsion angles of several Ala and Gly residues in the model peptide, GGAGGGYGGDGG(A)12GGA-GDGYGAG, were determined by the conformation-dependent 13C chemical shifts, rotational echo double resonance (REDOR) and 2D spin-diffusion NMR methods. The solid-state NMR analysis leads to the precise silk structure before spinning, where the poly-Ala sequence takes a typical alpha-helix pattern with a tightly winded helical structure at both terminal regions of the poly-Ala sequence. This is expected to stabilize the alpha-helical structure of the poly-Ala region in S. c. ricini silk fibroin from the silkworm.     

General synthesis of persistent trityl radicals for EPR imaging of biological systems

In this paper we describe the syntheses of the tetraoxygenated triarylmethyl (trityl) radical 14 and the tetrathiatriarylmethyl (trityl) radicals 15 and 16. The syntheses include new and improved preparations of the key intermediate compounds 1 and 2. The new route to compound 2 is noteworthy for its efficiency and its avoidance of the highly toxic compound phosgene as well as the isolation of the air-sensitive 1,2,4,5-benzenetetrathiol.