A Conia-Ene-Type Cyclization under Basic Conditions Enables an Efficient Synthesis of (−)-Lycoposerramine R

An enantioselective total synthesis of the Lycopodium alkaloid lycoposerramine R is presented. It relies on a base-mediated cyclization that resembles the Conia-ene reaction of ynones and gold-catalyzed variants thereof. Thus, hydrindanones and other functionalized ring systems bearing an exocyclic alkene can be rapidly accessed at room temperature without noble metal catalysis or substrate preactivation.     

Triboluminescence of Lanthanide Coordination Polymers with Face-to-Face Arranged Substituents

Luminescence upon the grinding of solid materials (triboluminescence, TL) has long been a puzzling phenomenon in natural science and has also attracted attention because of its broad application in optics. It has been generally considered that the TL spectra exhibit similar profiles as those of photoluminescence (PL), although they occur from distinct stimuli. Herein, we describe for the first time a large spectral difference between these two physical phenomena using lanthanide^III coordination polymers with efficient TL and PL properties. They are composed of emission centers (Tb^III and Eu^III ions), antenna (hexafluoroacetylacetonate=hfa), and bridging ligands (2,5-bis(diphenylphosphoryl)furan=dpf). The emission color upon grinding (yellow TL) is clearly different from that upon UV irradiation (reddish-orange PL) in Tb^III/Eu^III-mixed coordination polymers [Tb,Eu(hfa)₃(dpf)]_n (Tb/Eu=1). The results directly indicate the discrete excitation processes of PL and TL.     

Primal-dual path following method for nonlinear semi-infinite programs with semi-definite constraints

Mathematical Programming - In this paper, we propose a primal-dual path following method for nonlinear semi-infinite semi-definite programs with infinitely many convex inequality constraints,...     

Mechanofluorochromism of 1‐Alkanoylaminopyrenes

To create a new series of mechanofluorochromic materials and to elucidate the mechanism of the phenomenon of mechanofluorochromism, 1‐alkanoylaminopyrenes including 1‐acetylaminopyrene (AAPy), 1‐octanoylaminopyrene (OAPy), and 1‐stearoylaminopyren (SAPy) were prepared. It was found that these materials exhibited mechanofluorochromism with emission colors in the crystalline samples changing reversibly from bluish purple to yellowish green, which could be induced by mechanical grinding. X‐ray crystal structure analysis, electronic absorption, and fluorescence spectroscopies, as well as fluorescence lifetime analysis and powder X‐ray diffraction analysis of AAPy suggested that the present mechanofluorochromism was caused by developing crystal defects through grinding. Intermolecular hydrogen bonds were suggested to play an important role in the occurrence of mechanofluorochromism, suppressing the face‐to‐face overlapping of pyrene moieties to form excimers in the pristine crystal.     

Asymptotic distribution of the LR statistic for equality of the smallest eigenvalues in high-dimensional principal component analysis

This paper deals with the distribution of the LR statistic for testing the hypothesis that the smallest eigenvalues of a covariance matrix are equal. We derive an asymptotic null distribution of the LR statistic when the dimension p and the sample size N approach infinity, while the ratio p/N converging on a finite nonzero limit c(0,1). Numerical simulations revealed that our approximation is more accurate than the classical chi-square-type approximation as p increases in value.     

Mapping from a fragile glass-forming system to a simpler one near their glass transitions

Extensive molecular-dynamics simulations on two different glass-forming systems are performed to test the prediction proposed recently by the mean-field theory (MFT) of glass transition that a fragile system can be mimicked by a simpler one near their glass transitions. One is a simulation for a hard-sphere fluid with size polydispersity where the volume fraction φ is a control parameter and the other is for a Lennard-Jones binary mixture where the inverse temperature 1/T is a control parameter. Then, their mean-square displacements are fully analyzed by MFT. Thus, we show that both results are collapsed on a master curve given by MFT when , where is a long-time self-diffusion coefficient. We also investigate the non-singular behavior of consistently from a unified standpoint based on MFT. Thus, we show that macroscopic physical quantities in a fragile system can be transformed into those in a simpler one through a universal parameter .     

Absolute structure of prunustatin A, a novel GRP78 molecular chaperone down-regulator

In the course of our screening program for regulators of a molecular chaperone GRP78 expression, we isolated a novel inhibitor of GRP78 expression, designated as prunustatin A, from Streptomyces violaceoniger 4521-SVS3. The planar structure of prunustatin A was determined to be an oxidized type of the neoantimycin family. Its absolute stereochemistry was established to be 2R, 4S, 6S, 7R, 9S, and 29S by analyzing chemically degraded components obtained from the derivative of prunustatin A.     

Quenching and vibrational relaxation of SO(B3Sigma-, v' <or= 3) by collisions with Ar and N2

Fluorescence from a single vibronic level of SO(B3Sigma-, v' 相似文献   

Recognition of Amphiphiles with Many Pendent Galactose Residues byRicinus communisAgglutinin

Amphiphiles which carry many pendent galactose residues as side chains were prepared by telomerization of 2-methacryloyloxyethyl β-D-galactopyranoside (MEGal) or 3-(2-methacryloyl aminoethylthio)propylD-galactopyranoside (MEPGal, α:β = 3.9:1) using a lipophilic radical initiator. The galactose-carrying amphiphiles (DP (degree of polymerization) = 15) incorporated in liposomes were recognized by a lectin fromRicinus communis(RCA₁₂₀), which was proven by the increase in turbidity of the liposome suspension after mixing with the lectin. The recognition was largely affected by the distance between the galactose residues and the polymer main chain, and the surface density of the amphiphile in the liposomes. The liposomes containing these galactolipids were not taken up by mouse peritoneal macrophages, probably due to a steric hindrance of polymer main chains from the uptake of D-galactose receptors on the macrophages.