1,4-Addition of silicon dienoates to α,β-unsaturated aldehydes catalyzed by in situ-generated silicon Lewis acid

In situ-generated silyl methide species (R(3)Si-CTf(2)R') effectively catalyzed the reaction of β-substituted α,β-unsaturated aldehydes with silicon dienoates such as 3-bromo-2-TESO-furan to give the corresponding γ-adducts with excellent 1,4-selectivity and good anti selectivity.     

Specific crystal structure of poly(3-hydroxybutyrate) thin films studied by infrared reflection–absorption spectroscopy

Infrared reflection–absorption (IR-RAS) and transmission spectra were measured for poly(3-hydroxybutyrate) (PHB) thin films to explore its specific crystal structure in the surface region. As IR-RAS is sensitive to the vibration mode of perpendicular orientation of the surface, differences between IR-RAS and transmission spectra indicate an orientation of the lamella structure in the surface of PHB thin films. The relative intensity of the crystalline CO stretching band in the IR-RAS spectrum is significantly weaker than that in the transmission spectrum. It may be concluded that the transient dipole moment of the CO stretching mode of the crystalline state is not oriented perpendicular but nearly parallel to the substrate surface. On the other hand, the relative intensity of the band at 3009 cm⁻¹ due to the C–H stretching mode of the C–HOC hydrogen bonding is similar between the IR-RAS and transmission spectra, suggesting that the C–H bond is oriented neither perpendicular nor parallel to the substrate surface but in an intermediate direction. Since the CO group of the C–HOC hydrogen bonding is oriented nearly parallel to the surface and its C–H group is in the intermediate direction, it is very likely that the C–HOC hydrogen bonding has a somewhat bent structure. These results are in good agreement with our previous conclusion that the C–HOC hydrogen bonding of PHB exists along the a-axis (not the b-axis) between the CH₃ group of one helix and the CO group of another helix.     

Stereoselective one-pot three-component coupling approach towards the synthesis of the AC ring system of taxanes

The stereoselective one-pot three-component coupling reaction was accomplished by 1,4-addition of the protected cyanohydrin ether 9f to cyclohexenone 10g and subsequent addition of the resulting enolate to formaldehyde in high yield for the formation of the AC ring system of taxanes. We found that the bulky substituents at the 10-position in the A ring prevent the desired 1,4-addition. Similarly, the bulky trialkylsiloxy groups at the 4-position in the C ring prevent the 1,4-addition and electron-donating alkoxy groups at the same position induce the undesired retro-Michael reaction.     

Pulse radiolysis study of ion-species effects on the solvated electron in alkylammonium ionic liquids

The spectra and kinetic behavior of solvated electrons (e_sol⁻) in alkyl ammonium ionic liquids (ILs), i.e. N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide (DEMMA-TFSI), N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium tetrafluoroborate (DEMMA-BF₄), N,N,N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide (TMPA-TFSI), N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (PP13-TFSI), N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide (P13-TFSI), and N-methyl-N-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide (P14-TFSI) were investigated by the pulse radiolysis method. The e_sol⁻ in each of the ammonium ILs has an absorption peak at 1100 nm, with molar absorption coefficients of 1.5–2.3×10⁴ dm³ mol⁻¹ cm⁻¹. The e_sol⁻ decayed by first order with a rate constant of 1.4–6.4×10⁶ s⁻¹. The reaction rate constant of the solvated electron with pyrene (Py) was 1.5–3.5×10⁸ dm³ mol⁻¹ s⁻¹ in the various ILs. These values were about one order of magnitude higher than the diffusion-controlled limits calculated from measured viscosities. The radiolytic yields (G-value) of the e_sol⁻ were 0.8–1.7×10⁻⁷ mol J⁻¹. The formation rate constant of e_sol⁻ in DEMMA-TFSI was 3.9×10¹⁰ s⁻¹. The dry electron (e_dry⁻) in DEMMA-TFSI reacts with Py with a rate constant of 7.9×10¹¹ dm³ mol⁻¹ s⁻¹, three orders of magnitude higher than that of the e_sol⁻ reactions. The G-value of the e_sol⁻ in the picosecond time region is 1.2×10⁻⁷ mol J⁻¹. The capture of e_dry⁻ by scavengers was found to be very fast in ILs.     

Creation and application of psychoactive designer drugs data library using liquid chromatography with photodiode array spectrophotometry detector and gas chromatography-mass spectrometry

In order to quickly confirm a potentially hazardous psychoactive designer drug (a compound in which part of the molecular structure of a stimulant or narcotic has been modified), we created a psychoactive drugs data library by performing analysis using liquid chromatography with photodiode array spectrophotometry (LC/PDA) and gas chromatography-mass spectrometry (GC/MS). The data in this library consist of the LC capacity factor (k′) ratios in relation to the internal standard, the ultraviolet (UV) spectra and the MS spectra of 104 compounds. By performing a comparative study of the data in this report with the analytical data for commercial and illegal drug products, it is possible to quickly identify the psychoactive designer drugs in 205 purchased products by using the library. Further, it is possible to analogize the structure of drugs for which there is no matching data in the library using similar data.Furthermore, when structural isomers of controlled substances have detected from the presented library, similarity of their biological effects on human will be predicted, thus leading to regulate their public circulation. Examples of these types of isomers include, for instance, the narcotic 3,4,5-trimethoxyamphetamine (TMA) and its positional isomers 2,4,5-trimethoxyamphetamine (TMA-2) and 2,4,6-trimethoxyamphetamine (TMA-6), or the narcotic 1-(3-chlorophenyl)piperazine (3CPP) and its isomers 1-(o-chlorophenyl)piperazine (2CPP) and 1-(p-chlorophenyl)piperazine (4CPP). Differentiation of these compounds is necessary in regulating them, and we report here the results of a study of a method to confirm these compounds using the present library.     

Evolved gas analysis of Ti(C5H5)2Cl2 by means of Li+ ion attachment mass spectrometry

Characterization of the compound Ti(C(5)H(5))(2)Cl(2) was studied using Li(+) ion attachment mass spectrometry (IAMS) as an analytical methodology. Since this target compound is used as an anticancer drug in the treatment of leukemia, accurate and rapid monitoring methods for the determination of titanium drugs in a hospital environment are desirable. A quadrupole mass spectrometry system along with a Li(+) ion attachment technique and a direct inlet probe (DIP) produced the Li(+) adduct of Ti(C(5)H(5))(2)Cl(2), Ti(C(5)H(5))(2)Cl(2)Li(+). The DIP also was used to study the temperature-resolved behavior of this compound. The slope of the plot of signal intensity of Ti(C(5)H(5))(2)Cl(2)Li(+) versus temperature for Ti(C(5)H(5))(2)Cl(2) sublimation from 60 to 100 °C was used to determine an apparent activation energy (E(a)) of 124.43 kJ/mol for the sublimation of Ti(C(5)H(5))(2)Cl(2). This value is comparable to the reported value of 118.8 kJ/mol for molar enthalpy of sublimation of Ti(C(5)H(5))(2)Cl(2). These results demonstrate that the IAMS methodology can be used to study the enthalpy of sublimation for d-metal complex materials.     

Metachromins L-Q, new sesquiterpenoid quinones with an amino acid residue from sponge Spongia sp.

Six new sesquiterpenoid quinones with an amino acid residue, metachromins L-Q (1-6), have been isolated from an Okinawan marine sponge Spongia sp. The structures and stereochemistry of 1-6 were elucidated on the basis of the spectroscopic data and chemical correlations. Metachromins L (1) and M (2) showed modest cytotoxicity.     

Seven novel seco-prezizaane-type sesquiterpenes from the pericarps of Illicium merrillianum

Seven new seco-prezizaane-type sesquiterpenes were isolated from the methanol extract of the pericarps of Illicium merrillianum. Their structures were elucidated as 3-deoxypseudoanisatin (1), 2beta-hydroxy-3,6-dedioxypseudoanisatin (2), 8alpha-hydroxy-10-deoxycyclomerrillianolide (3), 10beta-hydroxypseudoanisatin (4), 10beta-hydroxycyclopseudoanisatin (5), 1,6-dihydroxy-3-deoxyminwanensin (6), and 8-deoxymerrilliortholactone (7) by analyses of their spectroscopic data and chemical transformation. Compounds 4 and 5 as well as 6 and 7 coexist as a keto/acetal equilibrated mixture in methanol solution.     

Preparation, structure, and properties of tetranuclear vanadium(III) and (IV) complexes bridged by diphenyl phosphate or phosphate

Three novel tetranuclear vanadium(III) or (IV) complexes bridged by diphenyl phosphate or phosphate were prepared and their structures characterized by X-ray crystallography. The novel complexes are [{V(III)(2)(μ-hpnbpda)}(2){μ-(C(6)H(5)O)(2)PO(2)}(2)(μ-O)(2)]·6CH(3)OH (1), [{V(III)(2)(μ-tphpn)(μ-η(3)-HPO(4))}(2)(μ-η(4)-PO(4))](ClO(4))(3)·4.5H(2)O (2), and [{(V(IV)O)(2)(μ-tphpn)}(2)(μ-η(4)-PO(4))](ClO(4))(3)·H(2)O (3), where hpnbpda and tphpn are alkoxo-bridging dinucleating ligands. H(3)hpnbpda represents 2-hydroxypropane-1,3-diamino-N,N'-bis(2-pyridylmethyl)-N,N'-diacetic acid, and Htphpn represents N,N,N',N'-tetrakis(2-pyridylmethyl)-2-hydroxy-1,3-propanediamine. A dinuclear vanadium(IV) complex without a phosphate bridge, [(VO)(2)(μ-tphpn)(H(2)O)(2)](ClO(4))(3)·2H(2)O (4), was also prepared and structurally characterized for comparison. The vanadium(III) center in 1 adopts a hexacoordinate structure while that in 2 adopts a heptacoordinate structure. In 1, the two dinuclear vanadium(III) units bridged by the alkoxo group of hpnbpda are further linked by two diphenylphosphato and two oxo groups, resulting in a dimer-of-dimers. In 2, the two vanadium(III) units bridged by tphpn are further bridged by three phosphate ions with two different coordination modes. Complex 2 is oxidized in aerobic solution to yield complex 3, in which two of the three phosphate groups in 2 are substituted by oxo groups.     

Fragmentation study of peptides using Fourier transform ion cyclotron resonance with infrared multiphoton dissociation: experiment and simulation

In this study, the fragmentation of gas-phase protonated Angiotensin II is investigated using electrospray ionization (ESI), Fourier-transform ion cyclotron resonance (FT-ICR), and mass spectrometry (MS) with a laser cleavage infrared multiphoton dissociation (IRMPD) technique. The experimental results show that the spectra peaks for the photoproducts are y2/b6- and y7-type ions, corresponding to the cleavage of His-Pro and Asp-Arg in the parent amino acid sequence. The fragmentation of the peptide under collision-free vacuum conditions is modeled using molecular dynamics simulations (MD). The binding energy for the peptide bonds (C'-N bond) of Angiotensin II is estimated from ab initio calculations. The calculations are directed at predicting experimental measurements of the product ions from the photodissociation of the peptide. The product distributions simulated by the MD dissociation trajectories include predominantly y7/b1 and y2/b6 pair ions.