Modification of nitroxyl contrast agents with multiple spins and their proton T(1) relaxivity

The purpose of this study is to test the performance of multispin nitroxyl contrast agents in improving the sensitivity of MR detection for nitroxyl contrast agents. The relation between T(1) relaxivity and the number of paramagnetic centers in a molecule was investigated. Compound 1 is a single molecule of methoxycarbonyl-PROXYL (MC-PROXYL). Two and three MC-PROXYL molecules were chemically coupled to obtain Compounds 2 and 3, which have two and three nitroxyl spins in the molecule, respectively. A good linear relation, the slope of which increased depending on the number of nitroxyl spins in the molecule, was obtained between T(1)-weighted (fast low-angle shot) MR image contrast enhancement at 7 T and the concentration of nitroxyl contrast agents. T(1)-weighted MR image contrast enhancement and T(1) relaxivity levels of nitroxyl contrast agents were increased depending on the number of nitroxyl spins in the molecule. Multicoupling nitroxyl molecules can enhance the T(1)-weighted contrast effect while maintaining the quantitative behavior of the molecule for up to three spins.     

A measurement method of the magnetic properties of magnetic sheet by means of a single sheet tester at audio frequency

A single sheet tester (SST) for audio frequency of 400 Hz–10 kHz was made experimentally and the magnetizing winding can get the nearly uniform distribution of flux density of a specimen in the longitudinal direction at the frequency up to 10 kHz. The flux densities at various positions of strips measured by the Epstein method were detected by search coils wound on strips at 400 Hz and 1.0 T. They have large discrepancy. However, the magnetic properties obtained from both methods have a little discrepancy. Although the uniformity of flux distribution in the Epstein frame is not sufficient, the average is fairly effective because the magnetic properties can be assumed to be locally linear within the small deviation of flux density.     

Studies on nucleosides and nucleotides. X. desulfurization of 2′,3′-0-Isopropylidene-2-thiouridines by dibenzoyldiazene

The reaction of dibenzoyldiazene with 2′,3′-0-isopropylidene derivatives of 2-thioridine, 5-methyl-2-thiouridine, and 5-methoxycarbonylmethyl-2-thio-uridine afforded the corresponding desulfurized products, $\text{3a}$-$\text{3c}$.     

2-Alkoxycarbonylallyltrimethylsilanes as new reagents of 2-alkoxycarbonylallylation of electrophiles

2-Alkoxycarbonylallylsilanes are useful for 2-alkoxycarbonylallylation of acetals and carbonyl compounds with an aid of a Lewis acid; the products can be readily converted to α-methylene-γ-butyrolactones.     

Intermetallic phase formation in electrochemical alloy deposition

Three examples of the electrochemical deposition of intermetallic phases are shown. Electrodeposition of the single-phase -brass superlattice at underpotentials of Zn in Cu-Zn alloy plating is explained by an accumulative underpotential deposition (UPD) mechanism. Growth of the Cu-Sn intermetallic phase layer in the contact immersion deposition of Sn onto Cu is accounted for by a UPD/vertical solid-state diffusion mechanism. Ag₃Sn formation in the Sn/Ag-nanoparticle composite plating is illustrated by atomic site exchange at the interface between the deposited Sn matrix and the occluded Ag nanoparticles.     

Selective scavenging property of the indole moiety for the nitrating species of peroxynitrite

The inhibitory effect on tyrosine nitration and oxidation of peroxynitrite was evaluated for more than 40 reagents including natural and synthetic compounds, and the inhibiting efficiency of each compound for nitration was compared with that for oxidation, to characterize its property as a peroxynitrite scavenger. In the presence of various concentrations of testing compounds, the nitrating and oxidizing activities were measured by monitoring the formation of 3-nitrotyrosine and dityrosine with an HPLC-UV-fluorescence detector. The IC(50) values for nitration and oxidation were determined, and the ratio of these two IC(50) values was calculated for each compound. Although the IC(50) values varied from compound to compound, it was revealed that the ratio of two IC(50) values (IC(50) for oxidation/IC(50) for nitration) was 1 in almost all the compounds tested, except five indole derivatives (L-tryptophan, melatonin, 5-methoxytryptamine, tryptamine, and tetrahydro-beta-carboline) and one synthetic selenium-containing compound ((2R,3R,4S)-2-amino-3,4-dihydroxy-5-phenylselenopentan-1-ol, ADPP). The indole derivatives showed a specific inhibitory effect on tyrosine nitration without affecting the oxidation. ADPP was confirmed to have a preferable inhibitory activity for tyrosine oxidation. It was suggested that compounds showing an IC(50) value ratio of 1 scavenged the common species for nitration and oxidation, while the indole derivatives and ADPP preferably scavenged the nitrating and oxidizing species, respectively. From a stopped flow study, it was also revealed that the nitrotyrosine formation was relatively slow, unlike an OH radical reaction. These results imply that the peroxynirite reaction at least partly proceeds through specific species for nitration.     

Catalytic double carbonylation of organohalogen compounds promoted by palladium complexes

Various organohalogem compounds can be catalytically converted into α-keto amides on reaction with carbon monoxide and amines. Tertiary phosphine-coordinated palladium compounds are particularly suitable as the double carbonylation catalyst.