Photoionization-induced water migration in the hydrated trans-formanilide cluster cation revealed by gas-phase spectroscopy and ab initio molecular dynamics simulation

Photoionization-induced water migration in the trans-formanilide-water 1:1 cluster, FA-(H(2)O)(1), has been investigated by using IR-dip spectroscopy, quantum chemical calculations, and ab initio molecular dynamics simulations. In the S(0) state, FA-(H(2)O)(1) has two structural isomers, FA(NH)-(H(2)O)(1) and FA(CO)-(H(2)O)(1), where a water molecule is hydrogen-bonded (H-bonded) to the NH group and the CO group, respectively. In addition, the S(1)-S(0) origin transition of FA(CO)-(H(2)O)(2), where a water dimer is H-bonded to the CO group, was observed only in the [FA-(H(2)O)(1)](+) mass channel, indicating that one of the water molecules evaporates completely in the D(0) state. These results are consistent with a previous report [Robertson, E. G. Chem. Phys. Lett., 2000, 325, 299]. In the D(0) state, however, [FA-(H(2)O)(1)](+) produced by photoionization via the S(1)-S(0) origin transitions of FA(NH)-(H(2)O)(1) and FA(CO)-(H(2)O)(1) shows essentially the same IR spectra. Compared with the theoretical calculations, [FA-(H(2)O)(1)](+) can be assigned to [FA(NH)-(H(2)O)(1)](+). This means that the water molecule in [FA-(H(2)O)(1)](+) migrates from the CO group to the NH group when [FA-(H(2)O)(1)](+) is produced by photoionization of FA(CO)-(H(2)O)(1). [FA-(H(2)O)(1)](+) produced by photoionization of FA(CO)-(H(2)O)(2) also shows the IR spectrum corresponding to [FA(NH)-(H(2)O)(1)](+). In this case, the water migration from the CO group to the NH group occurs with the evaporation of a water molecule. Ab initio molecular dynamics simulations revealed the water migration pathway in [FA-(H(2)O)(1)](+). The calculations of classical electrostatic interactions show that charge-dipole interaction between FA(+) and H(2)O induces an initial structural change in [FA-(H(2)O)(1)](+). An exchange repulsion between the lone pairs of the CO group and H(2)O in [FA-(H(2)O)(1)](+) also affects the initial direction of the water migration. These two factors play important roles in determining the initial water migration pathway.     

Hg2+-sensing system based on structures of complexes

The first example of a new Hg(2+)-sensing system based on the structures of complexes is reported. The system uses a combination of a new chiral bidentate ligand and CD spectroscopy. Significant CD spectral changes are observed when Hg(2+) is added, whereas no CD spectral changes are observed in the cases of Li(+), Na(+), K(+), Mg(2+), Ca(2+), Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Rb(+), Ag(+), Cd(2+), La(3+), Gd(3+), and Pb(2+).     

Preparation of a variety of fluoroalkyl end‐capped N‐(1,1‐dimethyl‐3‐oxobutyl)acrylamide oligomer/silica nanocomposites possessing no weight loss characteristic at 800°C

A variety of fluoroalkyl end‐capped N‐(1,1‐dimethyl‐3‐oxobutyl)acrylamide oligomer [R_F‐(DOBAA)_n‐ R_F]/silica nanocomposites, in which the oligomer contents are 18–96%, were prepared by reactions of the corresponding fluorinated oligomer with tetraethoxysilane and silica nanoparticles under alkaline conditions. Each fluorinated oligomer/silica composite thus obtained is nanometer size‐controlled very fine particles (22–68 nm) possessing a good dispersibility and stability in a variety of solvents including water. Interestingly, the weight loss of R_F‐(DOBAA)_n‐R_F/silica nanocomposites, in which the oligomer contents are 18–72%, were not observed at all even at 800°C, as well as the original silica nanoparticles, although the corresponding sub‐micrometer size‐controlled R_F‐ (DOBAA)_n‐R_F/silica composites (particle size: 359 nm) decomposed completely at 800°C to afford the weight loss in proportion to the content of R_F‐(DOBAA)_n‐R_F oligomer in composites. On the other hand, a slight weight loss of R_F‐(DOBAA)_n‐R_F/silica nanocomposites, in which the oligomer contents are 75–94%, was observed at 800°C compared to that of the original silica nanoparticles. Copyright © 2008 John Wiley & Sons, Ltd.     

Electronic stress tensor analysis of molecules in gas phase of CVD process for gesbte alloy

We analyze the electronic structure of molecules which may exist in gas phase of chemical vapor deposition process for GeSbTe alloy using the electronic stress tensor, with special focus on the chemical bonds between Ge, Sb, and Te atoms. We find that, from the viewpoint of the electronic stress tensor, they have intermediate properties between alkali metals and hydrocarbon molecules. We also study the correlation between the bond order which is defined based on the electronic stress tensor, and energy‐related quantities. We find that the correlation with the bond dissociation energy is not so strong while one with the force constant is very strong. We interpret these results in terms of the energy density on the “Lagrange surface,” which is considered to define the boundary surface of atoms in a molecule in the framework of the electronic stress tensor analysis. © 2015 Wiley Periodicals, Inc.     

New constituents from the leaves of Morinda citrifolia

A new iridoid glycoside, citrifoside (1), and a new anthraquinone, 1,5,15-trimethylmorindol (2), together with 24 known compounds, were isolated from the leaves of Morinda citrifolia. The structures of the new compounds were elucidated by spectral data. 1,5,15-Trimethylmorindol (2) did not show significant cytotoxic activity by itself but showed cytotoxicity when combined with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), while citrifoside (1) did not show any activity even with TRAIL.     

Efficient synthesis from d-lyxonolactone of 2-acetamido-1,4-imino-1,2,4-trideoxy-l-arabinitol LABNAc, a potent pyrrolidine inhibitor of hexosaminidases

The synthesis from d-lyxonolactone of 2-acetamido-1,4-imino-1,2,4-trideoxy-l-arabinitol LABNAc proceeded in an overall yield of 25%; the enantiomer, 2-acetamido-1,4-imino-1,2,4-trideoxy-d-arabinitol DABNAc, was prepared from l-lyxonolactone. LABNAc and N-benzyl LABNAc are potent non-competitive inhibitors of d-hexosaminidase, whereas N-benzyl DABNAc exhibits weak competitive inhibition of the enzyme; this provides further evidence in support of Asano’s hypothesis that while d-imino sugar mimics inhibit d-glycohydrolases competitively, their l-enantiomers show non-competitive inhibition and in the case of iminofuranoses l-enantiomers are usually more potent inhibitors.     

Efficient functional molecule incorporation method to functionalized peptide nucleic acid (PNA): use in synthesis of labeled PNA oligomers

A novel efficient synthetic method for a functionalized PNA (peptide nucleic acid) is described, in which a functional molecule is incorporated in place of a nucleobase. Novel ω-AA-^BocPNA-OH (20-24, AA=amino acid) were designed as PNA precursor monomer units into which functional molecules could be incorporated efficiently. Compounds 20-24 reacted quantitatively with OSu (N-hydroxysuccinimidyl) active ester derivatives and isothiocyanate derivatives of commercial functional molecules to give target functionalized PNA monomer units 25-53. Various types of functionalized PNA monomer units could be efficiently incorporated into multiple predetermined positions in a PNA oligomer by SPPS (solid phase peptide synthesis) in the same way as for the four A(Cbz), G(Cbz), C(Cbz), and T PNA monomer units.     

Pentalenolactone biosynthesis. Molecular cloning and assignment of biochemical function to PtlH, a non-heme iron dioxygenase of Streptomyces avermitilis

The hydroxylase encoded by the ptlH (SAV2991) gene from the pentalenolactone gene cluster of Streptomyces avermitilis was cloned by PCR and expressed in Escherichia coli as an N-terminal His6-tag protein. Incubation of recombinant PtlH with (+/-)-1-deoxypentalenic acid (5) in the presence of Fe(II), alpha-ketoglutarate, and O2 gave (-)-11beta-hydroxy-1-deoxypentalenic acid (8), whose structure and stereochemistry were determined by a combination of 1H, 13C, COSY, HMQC, HMBC, and NOESY NMR. The steady-state kinetic parameters were kcat = 4.2 +/- 0.6 s-1 and Km (5) = 0.57 +/- 0.19 mM. 8 is a new intermediate in the conversion of the sesquiterpene pentalenene (3) to pentalenolactone (1).     

Dicationic (BINAP)palladium-catalyzed enantioselective aldol reaction of aldehydes with a silyl enol ether: a simplified practical procedure

The dicationic ((R)-BINAP)palladium-catalyzed enantioselective aldol reaction of benzaldehyde with 1-phenyl-1-trimethylsilylethene has been reinvestigated regarding the reaction conditions in the presence of ((R)-BINAP)palladium chloride and AgSbF₆ with 3 Å molecular sieves. The simplified practical procedure with 1 mol % catalyst loading realized the high performance of 98% yield and 76% ee with reliable reproducibility.