Transition metal salts-catalyzed aza-Michael reactions of enones with carbamates

Several transition metal salts were found to catalyze aza-Michael reactions of enones with carbamates efficiently. The catalytic activity was strongly dependent on the nature of the metal salts. While conventional Lewis acids such as BF(3).OEt(2), AlCl(3), or TiCl(4) showed lower activity, group 7-11 transition metal salts in higher oxidation states such as ReCl(5), Fe(ClO(4))(3).9H(2)O, RuCl(3).nH(2)O, OsCl(3).3H(2)O, RhCl(3).nH(2)O, PtCl(4).5H(2)O, or AuCl(3).H(2)O exhibited higher catalytic activity. [reaction: see text]     

Asymmetric synthesis of optically active α-substituted α-amino-H-phosphinates through resolution of 1,1-diethoxyethyl(aminomethyl)phosphinates

Both enantiomers of 1,1-diethoxyethyl(aminomethyl)phosphinates were prepared through chromatographic separation of a diastereomeric mixture derived from (S)-phenylethylamine and 1,1-diethoxyethyl-H-phosphinate. The individual enantiomer was transformed into α-substituted α-amino-H-phosphinate with high enantiomeric purity by a highly diastereoselective alkylation at the α-carbon on the basis of our previously developed method.     

New mu-opioid receptor agonists with phenoxyacetic acid moiety

New muq-opioid receptor (MOR) agonists containing 4-hydroxypiperidine, piperidine and piperazine moieties were synthesized and evaluated to find a peripheral opioid analgesic. Among the synthesized compounds, 12-[1-[3-(N,N-dimethylcarbamoyl)-3,3-diphenylpropyl]-4-hydroxypiperidin-4-yl]phenoxy]acetic acid (8: SS620) having phenoxyacetic acid and 4-hydroxypiperidine moieties showed the highest agonist potency on the MOR in an isolated guinea-pig ileum preparation, and it also had selectivity to the human MOR expressed in Chinese hamster ovary (CHO)-K1 cells compared with the same types of delta- and kappa-opioid receptors (DOR and KOR). In addition, compound 8 showed a 10 times more potent MOR agonist activity than loperamide. Furthermore, compound 8 showed a peripheral analgesic activity in vivo screening on rat.     

Screening effect diverts the swimming directions from diaphototactic to positive phototactic in a disk-shaped green flagellate Mesostigma viride

We found diaphototactic behavior (i.e. the cells swim perpendicularly with respect to the incident light) in a strain with colorless eyespot of a unicellular disk-shaped green flagellate Mesostigma viride. Lacking pigments completely in the eyespot, the screening effect in this strain was due only to the central part of the chloroplast whose cross section was thin. The diaphototaxis was most obvious when unilateral green stimulus light (520-580 nm) was given, whereas positive phototaxis appeared when given blue light (430-490 nm). The choice between diaphototaxis and (ordinary) phototaxis depended entirely on the transmission (%T) of the cell body against each wavelength of the stimulus: the green light penetrated well (%T > 90%), whereas the blue light was considerably shaded by the chloroplast (50% < %T < 70%). The fraction of positive phototactically behaving cells against each wavelength was in proportion to the front-to-back contrast value obtained at each individual wavelength. The fraction of diaphototaxis was inversely proportional to it. In addition, bilateral stimulus irradiations to wild-type cell with colored eyespot provided useful information about the principle of the diaphototactic steering.     

A scaling method for obtaining kinetic equations from the BBGKY hierarchy

Kinetic equations for the one-particle distribution function of dilute gases and plasmas and evolution equations for the variance of their fluctuations are obtained from the BBGKY hierarchy equations by using Mori's scaling method in an extended form.     

Nepalensinols D-G, new resveratrol oligomers from Kobresia nepalensis (Cyperaceae) as potent inhibitors of DNA topoisomerase II

Four new resveratrol oligomers, nepalensinols D-G, were isolated from the stem of Kobresia nepalensis (Cyperaceae). The structures were determined by detailed NMR spectral analysis. The compounds were assessed for their inhibitory activity against human topoisomerase II, a potential target of anti-tumor agents. These stilbenoids showed potent inhibitory activity against human topoisomerase II with IC50 values of 5-15 microM.     

Diastereoselective radical hydrogenation of alpha-(1-Hydroxyalkyl)vinyl sulfoxides and sulfones controlled by intramolecular hydrogen bonding

The reaction of (S)-alpha-(1-hydroxyalkyl)vinyl sulfoxides (S)-5 with alkyl radicals and tributyltin hydride gave the addition-hydrogenation products with high diastereoselectivity, whereas the reaction with (R)-alpha-(1-hydroxyalkyl)vinyl sulfoxides (R)-5 resulted in complete recovery of the starting sulfoxides. Stereoselective intramolecular hydrogen bonding between the hydroxy group and the diastereotopic sulfonyl oxygen led to high diastereoselectivity in the radical reaction of alpha-(1-hydroxyethyl)vinyl sulfone 12. An important role of intramolecular hydrogen bonding on the diastereoselectivity as well as the reactivity toward alkyl radicals is discussed.     

Diastereoselective synthesis of alpha,beta'-disubstituted aminomethyl(2-carboxyethyl)phosphinates as phosphinyl dipeptide isosteres

A new and efficient method has been developed for the diastereoselective synthesis of unnatural dipeptide analogues containing the metabolically stable phosphinic moiety, NH 2XaaPsi[P(O)OHCH 2]XaaOH, which mimics the transition state of tetrahedral geometry of a scissile peptide bond in hydrolysis by protease. The method is based upon stereospecific Michael addition of stereodefined alpha-aminoalkyl- H-phosphinates to acrylates and subsequent diastereoselective alkylation at the beta'-position of the resulting Michael adducts.     

A scaling method for deriving kinetic equations from the BBGKY hierarchy

On the basis of the scale covariance of correlation functions under a coarsegraining in space and time, the Boltzmann equation for neutral gases, the Balescu-Lenard-Boltzmann-Landau equation for dilute plasmas, and linear equations for the variances of fluctuations are derived from the BBGKY hierarchy equations with no short-range correlations at the initial time. This is done by using Mori's scaling method in an extended form. Thus it is shown that the scale invariance of macroscopic features affords a useful principle in nonequilibrium statistical mechanics. It is also shown that there existtwo kinds of correlation functions, one describing the interlevel correlations of the kinetic level with its sublevels and the other representing the fluctuations in the kinetic level.Partially financed by the Scientific Research Fund of the Ministry of Education.     

On the interpretation of multiplicative white noise

The interpretation of a stochastic differential equation as an approximation to a stochastic difference equation is discussed. A criterion is presented for determining which stochastic calculus should be used.