Chemical Dynamic Kinetic Resolution and S/R Interconversion of Unprotected α‐Amino Acids

Reported herein is the first purely chemical method for the dynamic kinetic resolution (DKR) of unprotected racemic α‐amino acids (α‐AAs), a method which can rival the economic efficiency of the enzymatic reactions. The DKR reaction principle can be readily applied for S/R interconversions of α‐AAs, the methodological versatility of which is unmatched by biocatalytic approaches. The presented process features a virtually complete stereochemical outcome, fully recyclable source of chirality, and operationally simple and convenient reaction conditions, thus allowing its ready scalability. A quite unique and novel mode of the thermodynamic control over the stereochemical outcome, including an exciting interplay between axial, helical, and central elements of chirality is proposed.     

Sooner and later waiting time problems for success and failure runs in higher order Markov dependent trials

The probability generating functions of the waiting times for the first success run of length k and for the sooner run and the later run between a success run of length k and a failure run of length r in the second order Markov dependent trials are derived using the probability generating function method and the combinatorial method. Further, the systems of equations of 2^.m conditional probability generating functions of the waiting times in the m-th order Markov dependent trials are given. Since the systems of equations are linear with respect to the conditional probability generating functions, they can be solved exactly, and hence the probability generating functions of the waiting time distributions are obtained. If m is large, some computer algebra systems are available to solve the linear systems of equations.This research was partially supported by the Natural Sciences and Engineering Research Council of Canada.     

Joint distributions of numbers of success-runs and failures until the first consecutivek successes

Joint distributions of the numbers of failures, successes and success-runs of length less thank until the first consecutivek successes are obtained for some random sequences such as a sequence of independent and identically distributed integer valued random variables, a {0, 1}-valued Markov chain and a binary sequence of orderk. There are some ways of counting numbers of runs with a specified length. This paper studies the joint distributions based on three ways of counting numbers of runs, i.e., the number of overlapping runs with a specified length, the number of non-overlapping runs with a specified length and the number of runs with a specified length or more. Marginal distributions of them can be derived immediately, and most of them are surprisingly simple.This research was partially supported by the ISM Cooperative Research Program (93-ISM-CRP-8).     

A study of contact methods in the application of large deformation dynamics in self-contact beam

Nonlinear Dynamics - This paper introduces a procedure in the field of computational contact mechanics to analyze contact dynamics of beams undergoing large overall motion with large deformations...     

Hypothesis tests for high-dimensional covariance structures

We consider hypothesis testing for high-dimensional covariance structures in which the covariance matrix is a (i) scaled identity matrix, (ii) diagonal matrix, or (iii) intraclass covariance matrix. Our purpose is to systematically establish a nonparametric approach for testing the high-dimensional covariance structures (i)–(iii). We produce a new common test statistic for each covariance structure and show that the test statistic is an unbiased estimator of its corresponding test parameter. We prove that the test statistic establishes the asymptotic normality. We propose a new test procedure for (i)–(iii) and evaluate its asymptotic size and power theoretically when both the dimension and sample size increase. We investigate the performance of the proposed test procedure in simulations. As an application of testing the covariance structures, we give a test procedure to identify an eigenvector. Finally, we demonstrate the proposed test procedure by using a microarray data set.

     

In vivo temporal EPR imaging for estimating the kinetics of a nitroxide radical in the renal parenchyma and pelvis in rats

The kinetics of a nitroxide radical in the renal parenchyma and pelvis in rats were investigated by employing an in vivo EPR imaging system equipped with a surface-coil-type resonator (SCR). The exposed kidney of a living rat was inserted into the single-turn coil of the SCR, with the renal major axis aligned with the direction of alternative magnetic field (B(1)). After the injection of nitroxide radical via the tail vein, EPR measurements were repeated. From the temporal EPR images of the kidney on the 2-D projection to the plane which is perpendicular to the direction of B(1,) the decay rate of nitroxide radical in the renal parenchyma and pelvis was estimated. The parenchymal decay rate was found to be significantly shorter than that for the pelvis.     

Molecular symmetry and biological activities of new symmetrical tris(2-aminoethyl)amine derivatives

In terms of molecular symmetry and bioactivity, new C3- and CS-symmetrical derivatives based on the tris(2-aminoethyl)amine scaffold were designed and synthesized. The synthesized compounds were evaluated for antiviral activity with herpes simplex virus type 1 (HSV-1) by a plaque reduction assay and for cytotoxic activity with Vero cells. Most of the compounds showed no significant anti-HSV-1 activity, but some of the symmetrical derivatives showed high levels of cytotoxic activitiy.     

Palladium‐Catalyzed Aerobic Intermolecular Cyclization of Acrylic Acid with 1‐Octene to Afford α‐Methylene‐γ‐butyrolactones: The Remarkable Effect of Continuous Water Removal from the Reaction Mixture and Analysis of the Reaction by Kinetic,ESI‐MS,and XAFS Measurements

Further study of our aerobic intermolecular cyclization of acrylic acid with 1‐octene to afford α‐methylene‐γ‐butyrolactones, catalyzed by the Pd(OCOCF₃)₂/Cu(OAc)₂ ? H₂O system, has clarified that the accumulation of water generated from oxygen during the reaction causes deactivation of the Cu cocatalyst. This prevents regeneration of the active Pd catalyst and, thus, has a harmful influence on the progress of the cyclization. As a result, both the substrate conversion and product yield are efficiently improved by continuous removal of water from the reaction mixture. Detailed analysis of the kinetic and spectroscopic measurements performed under the condition of continuous water removal demonstrates that the cyclization proceeds in four steps: 1) equilibrium coordination of 1‐octene to the Pd acrylate species, 2) Markovnikov‐type acryloxy palladation of 1‐octene (1,2‐addition), 3) intramolecular carbopalladation, and 4) β‐hydride elimination. Byproduct 2‐acryloxy‐1‐octene is formed by β‐hydride elimination after step 2). These cyclization steps fit the Michaelis–Menten equation well and β‐hydride elimination is considered to be a rate‐limiting step in the formation of the products. Spectroscopic data agree sufficiently with the existence of the intermediates bearing acrylate (Pd? O bond), η³‐C₈H₁₅ (Pd? C bond), or C₁₁H₁₉O₂ (Pd? C bond) moieties on the Pd center as the resting‐state compounds. Furthermore, not only Cu^II, but also Cu^I, species are observed during the reaction time of 2–8 h when the reaction proceeds efficiently. This result suggests that the Cu^II species is partially reduced to the Cu^I species when the active Pd catalytic species are regenerated.     

Zamamidine C, 3,4-dihydro-6-hydroxy-10,11-epoxymanzamine A, and 3,4-dihydromanzamine J N-oxide, new manzamine alkaloids from sponge Amphimedon sp.

New manzamine alkaloids, zamamidine C (1), 3,4-dihydro-6-hydroxy-10,11-epoxymanzamine A (2), and 3,4-dihydromanzamine J N-oxide (3), have been isolated from an Okinawan marine sponge Amphimedon species. The structures and stereochemistries of 1-3 were elucidated from the spectroscopic data and chemical derivatization. Zamamidine C (1) is a new manzamine alkaloid possessing a second β-carboline ring via an ethylene unit at N-2 of manzamine D, while 3,4-dihydro-6-hydroxy-10,11-epoxymanzamine A (2) is the first manzamine alkaloid possessing an epoxide ring at C-10 and C-11. Zamamidine C (1) showed significant antitrypanosomal activity against Trypanosoma brucei brucei, the parasite associated with sleeping sickness, and antimalarial activity against Plasmodium falciparum, the causative agent of malaria in vitro.