Preferential CO oxidation promoted by the presence of H2 over K-Pt/Al2O3

In preferential CO oxidation in H2-rich gas, K-Pt/Al2O3(K/Pt = 10) was very effective in decreasing CO concentration below 10 ppm in the 375-410 K range, and the turnover frequency of the K-Pt/Al2O3 was 20 times as high as that of Pt/Al2O3 at 353 K; furthermore, the activity of CO oxidation was promoted drastically by the presence of H2.     

Novel carbohydrate-appended metal complexes for potential use in molecular imaging

Seven discrete sugar-pendant diamines were complexed to the {M(CO)(3)}(+) ((99m)Tc/Re) core: 1,3-diamino-2-propyl beta-D-glucopyranoside (L(1)), 1,3-diamino-2-propyl beta-D-xylopyranoside (L(2)), 1,3-diamino-2-propyl alpha-D-mannopyranoside (L(3)), 1,3-diamino-2-propyl alpha-D-galactopyranoside (L(4)), 1,3-diamino-2-propyl beta-D-galactopyranoside (L(5)), 1,3-diamino-2-propyl beta-(alpha-D-glucopyranosyl-(1,4)-D-glucopyranoside) (L(6)), and bis(aminomethyl)bis[(beta-D-glucopyranosyloxy)methyl]methane (L(7)). The Re complexes [Re(L(1)-L(7))(Br)(CO)(3)] were characterized by (1)H and (13)C 1D/2D NMR spectroscopy which confirmed the pendant nature of the carbohydrate moieties in solution. Additional characterization was provided by IR spectroscopy, elemental analysis, and mass spectrometry. Two analogues, [Re(L(2))(CO)(3)Br] and [Re(L(3))(CO)(3)Br], were characterized in the solid state by X-ray crystallography and represent the first reported structures of Re organometallic carbohydrate compounds. Conductivity measurements in H(2)O established that the complexes exist as [Re(L(1)-L(7))(H(2)O)(CO)(3)]Br in aqueous conditions. Radiolabelling of L(1)-L(7) with [(99m)Tc(H(2)O)(3)(CO)(3)](+) afforded in high yield compounds of identical character to the Re analogues. The radiolabelled compounds were determined to exhibit high in vitro stability towards ligand exchange in the presence of an excess of either cysteine or histidine over a 24 h period.     

Novel synthesis of carbapenam by intramolecular attack of lactam nitrogen toward eta1-allenyl and eta3-propargylpalladium complex

When a THF solution of beta-lactam having propargyl phosphate was warmed in the presence of 5 mol % of Pd(2)(dba)(3) x CHCl(3), 20 mol % of a bidentate ligand, and sodium acetate (1.5 equiv) at 40 degrees C for 22 h, carbapenam was produced in high yield. In this reaction, the lactam nitrogen attacked the central carbon of a eta(3)-propargylpalladium complex, which was formed from propargyl phosphate and Pd(0).     

From penicillin to penem and carbapenem. VI1) : Synthesis of dethiathienamycin

A new C₃-unit substitution reaction at C-4 position of 4- acetoxyazetidinone derivative ($\text{1}$ and $\text{5}$) by tetraallyltin ($\text{2}$) in the presence of 1/10 eq. of BF₃-ether in methylene chloride is described. From 4-allylazetidinone derivative ($\text{3}$) via ylid intermediate ($\text{14}$) dethiathienamycin ($\text{16}$) was synthesized.     

Completely stereocontrolled synthesis of the right fragment of salinomycin,a polyether antibiotic,by means of the chelation-controlled grignard reaction

In the course of our synthetic study of salinomycin ($\text{1}$), an ionophorous polyether antibiotic, the γ-lactone ($\text{2}$) corresponding to the C-21～C-30 fragment (the right fragment) of $\text{1}$ was synthesized from D-mannitol and ethyl L-lactate as chiral starting materials. The complete stereocontrol for the construction of new chiral centers has been achieved by means of the chelation-controlled Grignard reaction and the tetrahydropyran synthesis via the acid catalyzed epoxide ring opening.     

Influence of amino acid side chain packing on Fe-methionine coordination in thermostable cytochrome C

Paramagnetic NMR and optical studies of the oxidized forms of mesophile Pseudomonas aeruginosa cytochrome c(551) and its quintuple mutant (F7A/V13M/F34Y/E43Y/V78I), and thermophile Hydrogenobacter thermophilus cytochrome c(552) demonstrated that the amino acid side chain packings in the protein interior influence the coordination bond between the heme iron and the axial methionine in the proteins. The strength of heme axial coordinations was found to correlate with the overall protein thermostability.     

Nature of the active component in the catalytic system prepared from titanium(III) chloride(AA), ethylaluminum dichloride,and tetrakis(dimethylamino)silane,in the polymerization of propylene

The chemistry of the titanium(III) chloride(AA)–ethylaluminum dichloride–tetrakis-(dimethylamino)silane system for the polymerization of propylene was studied. A complex of ethylaluminum dichloride with tetrakis(dimethylamino)silane was isolated. It was shown that this complex contains ethylaluminum dichloride and tetrakis(dimethylamino)silane in the ratio of 2:1. This complex with titanium(III) chloride is responsible for the polymerization activity.     

Antioxidant activity and Neurite outgrowth-enhancing activity of scorbamic acid and a red pigment derived from ascorbic acid

Abstract

L-Ascorbic acid (AA), known as vitamin C, can form browning products by a non-enzymatic process during storage and the browning products cause deterioration of agricultural products. In the browning reaction, a red pigment, 2,2´-nitrilodi-2(2´)-deoxy-L-ascorbic acid ammonium salt (NDA), is generated from AA via L-scorbamic acid (SCA) as an intermediate. However, the biological activities of SCA and NDA have not yet been clarified. In this study, we assayed the antioxidant activities of SCA and NDA using ABTS radical cation and their neurite outgrowth-enhancing activities in PC12 cells. SCA showed stronger radical-scavenging activity than that of AA, while NDA hardly showed any activity. SCA and NDA enhanced the neurite outgrowth induced by dibutyryl cyclic AMP after their incorporation into cells in the same manner as that of AA. The results indicated that SCA has antioxidant activity and that SCA and NDA have neurite outgrowth-enhancing activity.     

Polymerization of vinyl monomers by the reaction products of diphenyl sulphoxide with potassium

Diphenyl sulphoxide (DPSO) reacts with an equimolar amount of potassium (K) in tetrahydrofuran (THF) at ?78° to form a reddish-black solution, giving an electron spin resonance (ESR) signal only below ?70°. The signal is attributed to a very labile DPSO anion radical. The solution of DPSO-K (1/1) reaction products reacts further with another molecular amount of K at this temperature to give no ESR signal. The DPSO-K (1/1) reaction products initiates the polymerization of acrylonitrile (AN), but not the polymerizations of methyl methacrylate (MMA), styrene (St) or isoprene (IP). The active species of the solution initiating the polymerization of AN is assumed to be potassium benzene sulphenate from analyses of the solution and the infra-red spectrum of AN oligomers obtained using the complex. The DPSO-K (1/2) reaction products solution initiates the polymerization of MMA, St and IP as well as AN. The active species initiating the polymerization of MMA, St or IP is assumed to be phenylpotassium.