High-performance liquid chromatographic assay of sulbactam using pre-column reaction with 1,2,4-triazole

A high-performance liquid chromatographic (HPLC) method for the determination of sulbactam in human and rat plasma and urine has been developed. Sulbactam was reacted with 1,2,4-triazole to yield a product having an ultraviolet absorption maximum at 326 nm. The product was separated using reversed-phase HPLC from the regular components of plasma and urine with an ion-pair buffer at 50 degrees C and detected at the ultraviolet maximum. The limits of accurate determination were 0.2 and 1.0 micrograms/ml in plasma and urine, respectively. The coefficients of variation of inter- and intra-assays in human plasma spiked at 4.0 micrograms/ml (n = 5) were 1.02 and 3.05%, respectively. Coexisting cefoperazone, penicillins, or the alkaline degradation product(s) of sulbactam did not interfere in the sulbactam assay. The pharmacokinetic behaviour of sulbactam and cefoperazone coadministered to rats was estimated by moment analysis.     

Hexagonal columnar porphyrin assembly by unique trimeric complexation of a porphyrin dimer with pi-pi stacking: remarkable thermal behavior in a solid

On heating, syn-diporphyrin zinc complexes fused with bis(ethano)dimethoxyanthracene, the crystal structure of which showed a unique trimeric assembly, extruded one ethylene molecule at 240-310 degrees C to give a porphyrin-naphthoporphyrin diad, and the second retro-Diels-Alder reaction and concomitant decomposition of the methoxy groups occurred at 280-350 degrees C to give the anthraquinone-fused diporphyrin, while the first thermal conversion of the anti-diporphyrin zinc complex occurred in a much lower temperature range (180-230 degrees C).     

NMR and X-ray analyses of triethyl 3,7,11-triphenylcyclonona[1,2-b;4,5-b′;7,8-b″]tripyrrole-2,6,10-tricarboxylate: reinvestigation of crown vs saddle conformation of cyclononatripyrroles

From X-ray analyses of 3,7,11-triphenylcyclonona[1,2-b;4,5-b′;7,8-b″]tripyrrole-2,6,10-tricarboxylate (CNTP 1), the molecules existed as saddle forms in both crystals of 1·3ClPh and 1·1/2CHCl₃. In the former crystal, hydrogen bonds between pyrrolic hydrogen and ester carbonyl oxygen spread two-dimensionally, forming molecular sheets, between which the solvent molecules were included, while two independent molecules were bounded three-dimensionally by the hydrogen bonds in the latter. In CDCl₃, CNTP was observed to adopt a crown form, while interconversion of the conformers was observed in C₅D₅N.     

Synthesis of aminocyclohexitol via carbon-carbon bond-forming radical cyclization of oxime ether

The stannyl radical mediated-cyclization of oxime ether, derived from D-glucose, gave the aminocyclohexitol derivative. Stereoselective C-C bond forming cyclization proceeded via favorable conformers minimizing A(1,3)-strain between the oxime ether group and alpha-substituents.     

Kinetics of polymerization of N-carboxy amino acid anhydride in dimethyl sulfoxide

Various kinds of NCA's were polymerized in dimethyl sulfoxide (DMSO). DL -Alanine NCA polymerized at a fast rate without initiator, the rate being represented by R_p1 = k[M]^1/2. When the polymerization was carried out in chloroform in the presence of DMSO, the rate was represented by the equation, R_p2 = K₂[M][DMSO]^1/2. Glycine NCA and DL -α-amino-n-butyric acid NCA also polymerized at a fast rate in DMSO without initiator. On the other hand, N-methylglycine NCA, DL - and L -valine NCA and DL - and L -leucine NCA did not polymerize in DMSO without initiator.     

Studies on imidazole derivatives as chelating agents-V Investigations of the applicabilities of the azoimidazoles as metallochromic indicators

Applicabilities of several azoimidazoles as metallochromic indicators were investigated in the light of the general equations expressing the colour change of the visual chelatometric titrations. By using the stability constants of the nickel(II), copper(II), zinc(II) and cadmium(II) chelates, the useful pH ranges, titration errors and sharpness of colour changes were predicted theoretically and the usefulness of these reagents as indicators was established experimentally. The Cu(II)-EDTA-indicator system was also examined experimentally. The OH-containing azoimidazoles could be applied to the direct titration of copper, nickel, zinc, cadmium, lead and bismuth and to the titration of calcium and cobalt in the presence of Cu(II)-EDTA. Attempts were made to construct diagrams for the estimation of titration errors and sharpness of colour changes.     

Thermal and Photochemical Isomerization of Tetraaryl Tetrakis(trifluoromethyl)

The isomerization of tetraaryl tetrakis(trifluoromethyl)[4]radialenes was studied. When type II (all-Z) isomers of 5,6,7,8-tetraaryl-5,6,7,8-tetrakis(trifluoromethyl)[4]radialenes were heated in tetralin at 170-200 degrees C, isomerization occurred to give mixtures of four [4]radialenes in a ratio of ca. I:II:III:IV = 1:10:5:1. However, when the isomeric mixtures were heated in the solid state at the same temperature, selective isomerization took place to give type II isomers in good selectivity (>91%). Upon irradiation with light, the type II isomers first isomerized to mixtures of the four [4]radialene isomers (I:II:III:IV = 2:2:48:48) and then rearranged to cyclobuta[b]naphthalenes via a 6pi-electrocyclic reaction followed by 1,3-hydrogen migration.     

Heat-resistant polymers with thianthrene analog units. II . Aromatic polyamides

A series of polyamides which contained thianthrene, phenoxatiin, and dibenzo-p-dioxin units was synthesized from tricyclic fused-ring diamines and aromatic diacid chlorides by solution polycondensations at a low temperature. The amorphous polyisophthalamides were highly soluble in polar organic solvents, whereas some of the polyterephthalamides with a fair degree of crystallinity were insoluble. The solubility of the series of polyamides increased in the order of the dibenzo-p-dioxin-containing polymers < phenoxatiin-containing polymers < thianthrene-containing polymers. The thermal stability increased in the reverse order and the dibenzo-p-dioxinpolyamides were more thermostable than the corresponding open-chain polymers with diphenyl ether linkages. The polyamides derived from 2,8-oriented tricyclic diamines showed somewhat lower glass transition temperatures than those from 2,7-oriented diamines.     

Cationic polymerization of 1-phenyl-4-ethyl-2,6,7-trioxabicyclo[2.2.2]octane

Cationic polymerization of bicyclo ortho ester, 1-phenyl-4-ethyl-2,6,7-trioxabicyclo[2.2.2]octane, was carried out with Lewis acids and cation sources to obtain the polyether containing ester group in the side chain. It was found that boron trifluoride etherate was the most active initiator in the Lewis acids. Magnesium perchlorate and triphenylcarbenium tetrafluoroborate, which have lower nucleophilic counter ions, initiated effectively the polymerization of bicyclo ortho ester.     

Solid-phase tandem radical addition-cyclization reaction: triethylborane-induced reaction of oxime ethers anchored to polymer support

Tandem radical addition-cyclization of oxime ethers anchored to polymer support was studied. The reaction of oxime ethers with stannyl radical proceeded effectively by the use of triethylborane as a radical initiator. The alkyl radical addition-cyclization reactions of oxime ether connected with alpha,beta-unsaturated carbonyl group proceeded under iodine atom-transfer reaction conditions to give the functionalized azacycles via two carbon-carbon bonds-forming process.