Regiospecific cycloaddition reactions using functionalized isoprenylsilane and related compounds

1-Alkoxy-3-trimethylsilylmethyl- and 1-alkoxy-3-trimethylsilyl-l,3-butadienes ($\text{1}$) were newly prepared. The cycloaddition reactions of $\text{1}$ with various dienophiles including heterodienophiles were found to proceed very smoothly in a perfectly regiospecific mode.     

Asymmetric synthesis of 2-substituted-3-aminocarbonyl propionic acid

An asymmetric synthetic route to 2-substituted-3-aminocarbonyl propionic acid, which is the significant component of low-molecular-weight renin inhibitors, is described. The key step of this synthesis is diastereoselective alkylation by using chiral oxazolidinone and benzyl bromoacetate.     

10B quantitative determination in ppb range by particle tracks reading for boron neutron capture therapy

Quantitative determination of ppb-order ¹⁰B was carried out in a small number of cultured tumor cells by particle tracks by the ₁₀B(n,)⁷Li reactions using solid state nuclear track detector (SSNTD) for boron neutron capture therapy research. The detection limit of ¹⁰B concentration in tumor cells is less than 1·10^-3 ppm under our experimental conditions which permits the quantitative determination of ¹⁰B in a small number of boronated tumor cells (10⁵/ml = ca. 0.1 mg). Boron quantities in tumor cells determined were well compatible with the tumor cell killing effects of boron neutron capture therapy.     

A novel solvent dipole-induced rotational isomerism of 1-hxdroxy-2-pyridone in the excited singlet state

The title compound shows dual fluorescence depending on polarity of the solvent used. The fluorescence in the nonpolar solvent, cyclohexane, has a maximuni at 370 nm, while the fluorescence in the polar solvent, methanol, has a maximum at 400nm. The short and long wavelength fluorescences were assigned to the syn and anti conformers, respectively. From these observations one is allowed to conclude that a novel solvent dipole-induced rotational isomerism takes place in the excited singlet state.     

Application of negative chemical ionization mass spectrometry to the structure elucidation of perfluorochemicals and related compounds

The negative chemical ionization mass spectra of representative perfluorinated alkanes, cycloalkanes, ethers and tertiary amines have been examined, using Ar at about 0.5 torr as the reagent gas. The compounds chosen are typical of those under study as components of fluorochemical emulsion blood substitutes. Many such PFC's, particularly those with cyclic or branched structures, give intense molecular ions; most give simple spectra with a few major fragment ions at high mass, in marked contrast to the EI spectra which are dominated by m/e 69 (CF₃+) and 131 (C₃F₅+) of no value for structure elucidation. NCI-GC/MS is more sensitive than conventional EI-GC/MS and promises to be more generally useful for structure determination. Specific examples from the various classes will be presented, and their NCI and EI mass spectra compared.     

Syntheses and biological activities of renin inhibitors containing statine analogues

Syntheses and biological activities of dipeptide renin inhibitors that contain statine analogues are described. The key steps of the synthetic approach to dipeptide renin inhibitors are the asymmetric synthesis of 2(R)-substituted-3-aminocarbonylpropionic acids and the diastereoselective syntheses of (3S,4S)-statine analogues. These inhibitors (2,14-40) inhibited human renin in the 3-140 nM range. Inhibitor ES 6864 (2) was found to be a highly potent inhibitor of human renin (IC50: 4.6 x 10(-9) M) and showed high enzyme specificity. Oral administration of ES 6864 at 3 mg/kg to conscious, sodium-depleted marmosets inhibited plasma renin activity (PRA) more than 80% after 1 h.     

α-Carboxylation reaction of carbonyl compounds with bromomagnesium ureide-carbon dioxide adducts

Bromomagnesium ureide-carbon dioxide adducts, models of the carboxylated biotin complex, undergo caboxylation of a variety of carbonyl compounds in good yield.     

Chemiluminescence of CaH and AIH in the reaction of the metal atoms and formaldehyde

Chemiluminescence from the reaction of calcium and aluminum with various hydrogen containing compounds in a flowing gas system and in a heat pipe oven are described. Red chemiluminescence of CaH was observed in the reaction of calcium, and weak chemiluminescence of AlH was seen in the reaction of aluminum with formaldehyde (H₂CO). It is proposed that a reaction between metal atoms and formaldehyde may be used as a source of diatomic metallic hydrides.