Synthesis and optical resolution of aminophosphines with axially chiral C(aryl)-N(amine) bonds for use as ligands in asymmetric catalysis

N-Aryl indoline-type aminophosphines 1a-c were obtained in good yields by a nucleophilic aromatic substitution (S(N)Ar) reaction followed by silane reduction. Aminophosphine 1d was also prepared from 2,3-difluorobenzaldehyde (4) via dimethylhydrazone. Optical resolution of C(aryl)-N(amine) bond atropisomers was achieved using (S)-(+)-di-mu-chlorobis[2-[(dimethylamino)ethyl]phenyl-C(2),N]dipalladium(II) ((S)-10). The determination of absolute configuration and the investigation of the rotation barrier for C(aryl)-N(amine) bond axial stability of an aminophosphine 1 are described. Finally, the ability of the chiral phosphine ligand 1 is demonstrated in a catalytic asymmetric reaction, such as a palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate (up to 95% ee).     

Sliding behavior of water droplets on flat polymer surface

Flat films of methyl methacrylate-fluoroalkyl methacrylate copolymers were prepared, and their hydrophobicity was investigated. It was revealed that the F concentration directly affects the static hydrophobicity on the flat polymer surface in a systematic manner. Furthermore, the sliding behavior of a water droplet on these surfaces depends on the static hydrophobicity; the sliding motion changes from constant velocity to constant acceleration with an increase in the water contact angle.     

PLA2 inhibitory activity of marine sesterterpenoids cladocorans, their diastereomers and analogues

Inhibition of secretory phospholipase A(2) (sPLA(2)) by cladocorans A and B and their diastereomers almost equaled that of manoalide.     

New iridoid glucosides from the aerial parts of Verbena brasiliensis

Two new iridoid glucosides, verbenabraside A (1) and verbenabraside B (2), were isolated from the aerial parts of Verbena brasiliensis VELL., along with six known iridoid glucosides, gelsemiol 3-O-beta-D-glucoside (3), verbraside (4), 9-hydroxysemperoside (5), griselinoside (6), aralidioside (7), and 6alpha-hydroxyforsythide dimethyl ester (8), three known phenylethanoid glycosides, 2-phenylethyl O-beta-D-xylopyranosyl-(1-->2)-beta-D-glucopyranoside (9), acteoside (10), and leucosceptoside A (11), two known lignan glucosides, dihydroxymethyl-bis(3,5-dimethoxy-4-hydroxyphenyl) tetrahydrofuran-9 (or 9')-O-beta-glucopyranoside (12) and (+)-lyoniresinol 3alpha-O-beta-D-glucopyranoside (13), a known methyl salicylate glucoside, methyl 2-O-beta-D-glucopyranosylbenzoate (14), and two known sterols, beta-sitosterol 3-O-beta-D-glucopyranoside (15) and beta-sitosterol (16). Their chemical structures were determined on the basis of spectroscopic data. Compound 1 exhibited stronger scavenging effect on the stable free radical 1,1-diphenyl-2-picrylhydrazyl than that of alpha-tocopherol.     

Viologen-modified platinum clusters acting as an efficient catalyst in photocatalytic hydrogen evolution

A highly efficient photocatalytic system for hydrogen evolution with dihydronicotinamide coenzyme (NADH) as a sacrificial agent in an aqueous solution has been constructed by using water-soluble platinum clusters functionalized with methyl viologen-alkanethiol (MVA2+) and a simple electron-donor dyad, 9-mesityl-10-methylacridinium ion (Acr+-Mes), which is capable of fast photoinduced electron transfer but extremely slow back electron transfer. The mean diameter of the platinum core was determined as R(CORE) = 1.9 nm with a standard deviation sigma = 0.5 nm by transmission electron microscopy (TEM). As a result, the hydrogen-evolution rate of the photocatalytic system with MVA2+-modified platinum clusters (MVA2+-PtC) is 10 times faster than the photocatalytic system with the mixture of the same amount of MVA2+ and platinum clusters as that of MVA2+-PtC under otherwise the same experimental conditions. The radical cation of NADH has been successfully detected by laser flash photolysis experiments. The decay of the absorbance due to NAD*, produced by the deprotonation from NADH*+, coincides with the appearance of the absorption band due to Acr*-Mes. This indicates electron transfer from NAD* to Acr+-Mes to give Acr*-Mes, which undergoes the electron-transfer reduction of MVA2+-PtC, leading to the efficient hydrogen evolution.     

A comparative study of the fragmentation of neutral lactooligosaccharides in negative-ion mode by UV-MALDI-TOF and UV-MALDI ion-trap/TOF mass spectrometry

Structure analyses of underivatized neutral lacto oligosaccharides are systematically performed by ultraviolet matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (UV-MALDI TOF MS) and UV-MALDI ion-trap time-of-flight mass spectrometry (ion-trap/TOF MS) acquired in negative-ion mode. Interestingly, their fragmentation significantly differ each other. In postsource decay (PSD) in UV-MALDI TOF MS, cross-ring cleavage at the reducing terminal predominates. On the other hand, glycosyl bond cleavage (C-type fragmentation) takes place preferentially in collision induced dissociation (CID) in UV-MALDI ion-trap/TOF MS. The cross-ring cleavage in PSD similar to that in in-source decay occurs via a prompt reaction path characteristic of the UV-MALDI process itself. The product ion spectra of UV-MALDI ion-trap/TOF MS are similar to the electrospray ionization (ESI) ion-trap or quadrupole/TOF CID product ion spectra. During ion-trap/TOF MS experiments, the deprotonated molecular ions survive for several tens of milliseconds after CID event because the high internal energy chlorinated precursor ions are cooled by collisional cooling in the ion trap. The results obtained suggest that the PSD from the chlorinated precursor ion in UV-MALDI TOF MS might proceed as a two-step reaction; in the first, a high internal energy deprotonated molecular ion is generated as a reaction intermediate during the flight in the drift tube, and in the second, the rapid decomposition from the deprotonated molecular ion takes place.     

Magnetic hyperfine interaction of 59Fe in nickel

Nuclear magnetic resonance on oriented nuclei (NMR-ON) on ⁵⁹Fe isotope in Ni was performed. The magnetic hyperfine splitting frequency of was determined to be ν(B ₀?=?0)?=?48.32 (2) MHz. Using the known magnetic moment the magnetic hyperfine field was deduced as B _HF?=???28.32 (5) T. The effective nuclear spin-lattice relaxation time was also measured. The measured value is compared with experimental values of 3d-impurity in nickel host.     

Multiple-relaxation-time lattice Boltzmann model for the convection and anisotropic diffusion equation

A lattice Boltzmann model with a multiple-relaxation-time (MRT) collision operator for the convection–diffusion equation is presented. The model uses seven discrete velocities in three dimensions (D3Q7 model). The off-diagonal components of the relaxation-time matrix, which originate from the rotation of the principal axes, enable us to take into account full anisotropy of diffusion. An asymptotic analysis of the model equation with boundary rules for the Dirichlet and Neumann-type (specified flux) conditions is carried out to show that the model is first- and second-order accurate in time and space, respectively. The results of the analysis are verified by several numerical examples. It is also shown numerically that the error of the MRT model is less sensitive to the variation of the relaxation-time coefficients than that of the classical BGK model. In addition, an alternative treatment for the Neumann-type boundary condition that improves the accuracy on a curved boundary is presented along with a numerical example of a spherical boundary.     

Arrangements and Ranking Patterns

In the unidimensional unfolding model, given m objects in general position on the real line, there arise 1 + m(m − 1)/2 rankings. The set of rankings is called the ranking pattern of the m given objects. Change of the position of these m objects results in change of the ranking pattern. In this paper we use arrangement theory to determine the number of ranking patterns theoretically for all m and numerically for m ≤ 8. We also consider the probability of the occurrence of each ranking pattern when the objects are randomly chosen. Received March 5, 2005