Reactions of group IV organometallic compounds : XXVII. Some reactions of [(trimethylsilyl)imino]phosphorane

The reaction of [(trimethylsilyl)imino]methyldiphenylphosphorane: Ph₂MePNSiMe₃ (I) with several acid anhydrides or alkyl isocyanates took place by the simple cleavage of silicon-nitrogen bond. In contrast the interaction of (I) with phenyl isocyanate, isothiocyanate or carbon disulphide led to addition-elimination reactions of the Wittig type. Detailed investigation in the case of phenyl isocyanate indicated the usual elimination of Ph₂MePO is suppressed by the strong affinity of the trimethylsilyl group for anionic oxygen atom.     

Synthesis of (−)-terrecyclic acid A. Absolute configuration of terrecyclic acid A and quadrone

(?)-Terrecyclic acid A ($\text{15}$) was synthesized from (+)-fenchone ($\text{1}$). The absolute configuration of terrecyclic acid A and quadrone was established.     

Photoelectron spectra and angular distribution in reson three-photon ionization of atomic iron: J dependence

Kenetic energies and angular distributions of photoelectrons emitted by three-photon ionization fo atomic iron through two-photon resonant state e⁷D_J and e⁵ D_J, were measured, by using visible lasers. J-resolved photoelectron bands attributab to the a⁶D_J and a⁴F_j ionic states are reported.     

Observation of magnetic order of Cu-moment aroundx=0.12 in La2−x Ba x CuO4 and La2−x sr x CuO4 by μ+SR

Zero field positive muon spin rotation method ( ⁺SR) is applied on La_2–x Sr _x CuO₄ around forx=0.12 at which the high-T _c superconductivity (SC) is suppressed. The magnetically ordered state of Cu-moments, which is not a spin glass state but an antiferromagnetic like state, appears below 15 K for 0.105x0.120. The magnetic phase boundary is very similar to the one of the La_2–x Ba _x CuO₄ in which the structural transition from the low temperature orthorhombic (LTO) phase to the low temperature tetragonal (LTT) phase is observed aroundx=0.12. The present study suggests that there is no big difference of the electronic state of the CuO₂ plane between the La-Ba system and the La-Sr system and that the magnetic ordering of Cu-moments plays an important role for the suppression of the high-T _c SC aroundx=0.12 in both of the systems, although the LTO-LTT structural transition has not been observed yet in the La-Sr system.     

Spin dynamics in a site diluted finite spin cluster system probed by positive muons

The site diluted finite spin cluster system Rb₂CO _x Mg_1–x F₄ (x=0.15, 0.4, 0.5) has been investigated by the ⁺SR technique. Muon spin relaxation was observed in these diluted magnetic systems in a weak longitudinal field of 100 G. By reducing temperature below 100 K, the experimental data show features of slowing down phenomena of the Co electron moments in the finite spin clusters.     

Synthesis of 4-fluorinated UDP-MurNAc pentapeptide as an inhibitor of bacterial growth

4-Fluorinated UDP-MurNAc pentapeptide, 2, has been synthesized. In our previous study, UDP-MurNAc pentapeptide analogue 1 was found to be incorporated into the bacterial cell wall through biosynthesis. Compound 2 showed growth-inhibition activity against Gram-positive bacteria when it was added to growth media at 0.01 mg/mL. [structure--see text]     

Supramolecular hydrogels and organogels based on novel l-valine and l-isoleucine amphiphiles

New low-molecular-weight gelators based on l-valine and l-isoleucine gelators, which have a positively charged terminal group, can gel not only pure water and aqueous solutions containing inorganic acids and salts but also some organic solvents and oils.