Enantioselective total synthesis of (+)-ottelione A, (-)-ottelione B, (+)-3-epi-ottelione A and preliminary evaluation of their antitumor activity

Enantioselective total synthesis of (+)-ottelione A (1) and (-)-ottelione B (2), novel and potent antitumor agents from a freshwater plant, and (+)-3-epi-ottelione A (3), the earlier proposed stereostructure of 1, was efficiently achieved starting from the known tricyclic compound 10. The synthesis involved the following key steps: i) coupling reactions of aldehydes 8 and 9 with the aromatic portion 7 (8+7-->15 and 9+7-->27), ii) base-induced hemiacetal-opening/epimerization reactions of the cyclic hemiacetals 6 and 27 (6-->17 and 27 a-->26 a), and iii) Corey-Winter's reductive olefination of the cyclic thiocarbonates 21 and 36 (21-->22 and 36-->37). The present total synthesis fully established the absolute configuration of these natural products. The cell growth inhibition profile, COMPARE analysis, and tubulin inhibitory assay of (+)-3-epi-ottelione A (3) and its O-acetyl derivative 24 demonstrated that these unnatural substances could be prominent lead compounds for the development of anticancer agents with a novel mode of action.     

Thermolysis of reactive oligo(p-phenylene sulfide) containing disulfide bond

Oligo(phenylene sulfide) (OPS) containing one disulfide bond at the end of the chain, which was obtained by the oxidative polymerization of diphenyl disulfide, had a relatively low Td_10%(temperature for 10% weight loss) of 412 °C because of degradation of the disulfide bond. But this thermal cleavage of the disulfide bond promoted the curing reaction through thiophenoxy radical formation. OPS was allowed to react with diiodobenzene at 220 °C. The thermal stability of OPS was improved through the consumption of the disulfide bond and the coupling of the chain.     

On the bromine variations in mouse lymphoma

Bromine and chlorine concentrations in some tissues (liver, spleen, thymus) of healthy mice (normal group) and lymphomatous mice (lymphoma group) were determined by neutron activation analysis. There were significant differences in the Br concentrations of the tissues between the normal and lymphomatous group, while the Cl concentrations were found relatively constant in all the tissues. As a result, the Br/Cl ratios in the tissues of the lymphomatous group were significantly higher than those of the normal group. It was difficult to conclude that Br was absorbed into the bodies of lymphomatous mice more easily than was Cl. It is suggested that Br excretion from the body is suppressed.     

Concomitant increase in putrescine incorporation with transferrin uptake into rat reticulocytes.

Concomitant increase in putrescine incorporation with transferrin uptake into rat reticulocytes was found. [14C]Putrescine incorporation occurred in the presence of transferrin at 37 degrees C. The subcellular distribution of incorporated [14C]putrescine showed that the incorporation in the plasma membrane time dependently increased. Both 125I-labeled transferrin uptake and [14C]putrescine incorporation decreased when ethylene glycol bis(2-aminoethyl ether)-N,N,N',N'-tetraacetic acid was added, while it increased with the addition of A23187.     

Uneven distribution of ventilation—perfusion ratios in lungs estimated by a modified Newton method

The uneven distribution of ventilation—perfusion ratios ( ) in diseased lungs is the major cause of arterial hypoxemia. Farhi and Yokoyama (1967) and Yokoyama and Farhi (1967) were the first who used physiologically inert gases as indicator gases to assess the uneven distribution of Wagner and his coworkers in San Diego (1977b) extended the method and elaborated the multiple inert gas elimination technique in which blood flows in 50 compartments with different were estimated based on data for 6 indicator gases. They analyzed the indicator gas data through an enforced smoothing technique with the ridge regression. To get smooth distributions, they introduced a weighting function for compartments and an additional treatment for the non-negativity of the blood flow. The weighting function was empirically obtained. We analyzed the data without putting any weights on compartments nor any additional treatment for non-negativity of blood flow. The analytical method in the present study was a modified Newton method, which is one of the enforced smoothing method. Our method was capable of recovering all distribution patterns that were found through the method reported by Wagner et al. (1977b).     

Notes on the Problem of the Allocation of Resources to Activities in Discrete Quantities

The simple resource allocation problem (also called the distribution of effort problem) is generalized by allowing more than one resource constraint. It is shown that the generalized problem can be reduced to the simple one if the coefficients in the objective function are all unity. In general, however, the problem seems to become much more difficult; the difficulty is evidenced by the failure of the incremental method which is valid for the simple problem, and the NP-hardness of the generalized problem.     

End effects for a rodlike polyelectrolyte molecule in salt solution

Electrostatic potentials around a single rodlike polyelectrolyte molecule are calculated by solving the nonlinear Poisson–Boltzmann equation numerically in the presence of externally added salt. The polyion is regarded as a cylinder with a finite length whose side surface is uniformly charged and end surfaces uncharged. The calculations show that the distance to which end effects extend is about half the Debye screening length and is almost independent of the surface charge density and concentration of added salt. For a long polyion whose length is much greater than the Debye length, the end effects can be neglected even for a polyelectrolyte with high surface charges, whereas they play an important role for a short polyion with a length of the same order as the Debye length. In addition, a strong charge condensation is found in the direction of the axis of the cylinder for a long polyion.     

Photo-degradation of imidazolium ionic liquids

Degradation of imidazolium ionic liquid, [bmim⁺][TFSA⁻] and iodide solution of [bmim⁺][TFSA⁻] by UV-laser irradiation has been studied through ground-state absorption and transient absorption spectroscopy. We found that excited state [bmim⁺]* undergoes degradation efficiently.