Asymmetric Total Synthesis of (−)‐Englerin A through Catalytic Diastereo‐ and Enantioselective Carbonyl Ylide Cycloaddition

An asymmetric total synthesis of the guaiane sesquiterpene (?)‐englerin A, a potent and selective inhibitor of the growth of renal cancer cell lines, was accomplished. The basis of the approach is a highly diastereo‐ and enantioselective carbonyl ylide cycloaddition with an ethyl vinyl ether dipolarophile under catalysis by dirhodium(II) tetrakis[N‐tetrachlorophthaloyl‐(S)‐tert‐leucinate], [Rh₂(S‐TCPTTL)₄], to construct the oxabicyclo[3.2.1]octane framework with concomitant introduction of the oxygen substituent at C9 on the exo‐face. Another notable feature of the synthesis is ruthenium tetraoxide‐catalyzed chemoselective oxidative conversion of C9 ethyl ether to C9 acetate.     

Functionalized pyrolytic highly oriented graphite polymer film for surface‐assisted laser desorption/ionization mass spectrometry in environmental analysis

The pyrolytic highly oriented graphite polymer film (PGS) was first employed to analyze low‐mass analytes in environmental analysis by surface‐assisted laser desorption/ionization mass spectrometry (SALDI‐MS). PGS is a synthetic uniform and highly oriented graphite polymer film with high thermal anisotropic conductivity. We have found that negative ion mode SALDI‐MS using oxidized PGS (PGS‐SALDI‐MS) can be used to detect [M–H]^? ions from perfluorooctanoic acid (PFOA) and other perfluoroalkylcarboxylic acids when the PGS surface is modified with the cationic polymer polyethyleneimine (PEI). The signal intensity of PFOA when employing the PEI modification showed a ten‐fold increase over that obtained from desorption/ionization on porous silicon (DIOS). PFOA was quantified using PGS‐SALDI‐MS and the calibration curve showed a wide linear dynamic range of response (20–1000 ppb). The combination of atmospheric pressure ionization and PGS (AP‐PGS‐SALDI) showed greater signal intensity than vacuum PGS‐SALDI for deprotonated PFOA. Several other environmentally important chemicals, including perfluoroalkylsulfonic acid, pentachlorophenol, bisphenol A, 4‐hydroxy‐2‐chlorobiphenyl, and benzo[a]pyrene, were also successfully used to evaluate PGS‐SALDI‐MS. In addition, we found that nonafluoro‐1‐butanesulfonic acid was able to produce protonated peptides in positive ion PGS‐SALDI‐MS, but that perfluoropentanoic acid and trifluoroacetic acid were not. It is suggested that perfluoroalkylsulfonic acids are better protonating agents than perfluoroalkylcarboxylic acids in SALDI‐MS. Copyright © 2009 John Wiley & Sons, Ltd.     

Automated phosphoproteome analysis for cultured cancer cells by two-dimensional nanoLC-MS using a calcined titania/C18 biphasic column.

We have developed an on-line automated system for phosphoproteome analysis using titania-based phosphopeptide enrichment followed by nanoLC-MS/MS. Titania beads were prepared by calcination of commercial chromatographic titania beads at 800 degrees C to convert the crystalline structure. The obtained rutile-form titania exhibited higher selectivity in phosphopeptide enrichment than commercial titania, even in the absence of a competitive chelating reagent for non-phosphopeptides. For phosphoproteome analysis of human cervical cancer HeLa cells, tryptic digests of the cell extracts were directly injected into this on-line system, and 696 non-redundant phosphopeptides with 671 unambiguously determined phosphorylation sites, derived from 512 phosphoproteins, were successfully identified. This is the first successful application of an on-line automated phosphoproteome analysis system to complex biological samples.     

Equiaffine immersions of general codimension and its transversal volume element map

With an equiaffine immersion of codimension 1 into the affine space with the natural equiaffine structure, the conormal map is associated. In this paper, for an equiaffine immersion of general codimension into the space, we shall define the map corresponding to the conormal map, which is called the transversal volume element map. And we shall investigate if, an equiaffine immersion of general codimension into the space is determined by its affine fundamental form and its transversal volume element map.     

Scattering of flexural waves by a cracked Mindlin plate of soft ferromagnetic material in a uniform magnetic field

Consider the impingement of time harmonic flexural waves on a through crack in a soft ferromagnetic plate the surface of which is subjected to a uniform magnetic field at normal incidence. Mindlin's plate theory is used to account for the magneto-elastic interaction. For an incident wave that gives rise to moments symmetric about the crack plane, Fourier transforms are applied reducing the mixed boundary value problem to a Fredholm integral equation that can be solved numerically. The dynamic moment intensity factor versus frequency is computed to exhibit the influence of the magnetic field.     

Synthesis and magnetic properties of ALnO2 (A=Cu or Ag; Ln=rare earths) with the delafossite structure

Synthesis, structures, and magnetic properties of ternary rare earth oxides ALnO₂ (A=Cu or Ag; Ln=rare earths) have been investigated. CuLnO₂ (Ln=La, Pr, Nd, Sm, Eu) were synthesized by the direct solid state reaction of Cu₂O and Ln₂O₃, and AgLnO₂ (Ln=Tm, Yb, Lu) were obtained by the cation-exchange reaction of NaLnO₂ and AgNO₃ in a KNO₃ flux. These compounds crystallized in the delafossite-type structure with the rhombohedral 3R type (space group: R-3m). Magnetic susceptibility measurements showed that these compounds are paramagnetic down to 1.8 K. Specific heat measurements down to 0.4 K indicated that CuNdO₂ ordered antiferromagnetically at 0.8 K.     

A comparative study on acute toxicity of methylarsonic acid,dimethylarsinic acid and trimethylarsine oxide in mice

The acute toxicity of methylarsonic acid, CH₃AsO(OH)₂ (MAA), dimethylarsininc acid, (CH₃)₂AsO(OH) (DMAA), and trimethylarsine oxide, (CH₃)₃AsO (TMAO), were examined in mice with oral administration. The LD₅₀ values of MAA, DMAA and TMAO were 1.8, 1.2 and 10.6 g kg^?1 respectively. The toxicity of MAA and DMAA was very much lower than that for inorganic arsenic compounds. It was shown that TMAO has a similar acute toxicity to arsenobetaine. On the other hand, when the mice were administered 14.4 g kg^?1 of TMAO once only orally, a garlic-like odor (trimethylarsine, (CH₃)₃As) was definitely detectable in the exhalation of the animals by the human olfactory sense within about a few minutes.     

Decorated ising model with classical vector spins

A decorated Ising model with classical vector spins on a square lattice is investigated in detail. The partition function is reduced to the one of the Ising model with effective exchange integrals. Three successive phase-transition temperatures are obtained and four states, namely, paramagnetic, antiferromagnetic, again paramagnetic and ferromagnetic states are realized as the temperature is decreased. For systems on other two- and three-dimensional loose-packed lattices, the situation is the same as the system on the square lattice.