C-24 stereochemistry of marine sterols: (22E)-24-(isopropenyl)-22-dehydrocholesterol and 24-isopropenylcholesterol

The C-24 configuration of (22E,24xi)-24-isopropenyl-22-dehydrocholesterol (1), which was recently isolated from the Colombian Caribbean sponge, Topsentia ophiraphidites, was investigated. Synthesis of the stereodefined (24R)- and (24S)-(22E)-24-isopropenyl-22-dehydrocholesterols (1a, 1b) followed by (1)H- and (13)C-NMR data comparison of these sterols established the (24R)-configuration of 1. In addition, (24R)- and (24S)-24-isopropenylcholesterols (2a and 2b) were also synthesized and their NMR data are provided. The C-24 configurations of the samples of 24-isopropenylcholesterol reported previously are discussed.     

Total synthesis of COPD biomarker desmosine that crosslinks elastin

Desmosine, a crosslinking amino acid of elastin, is an attractive biomarker for diagnosis of chronic obstructive pulmonary disease (COPD). In this study, the first total synthesis of (+)-desmosine was achieved in 11% overall yield in 13 steps utilizing stepwise and regioselective Sonogashira cross-coupling reactions.     

On the Abel–Jacobi maps of Fermat Jacobians

We study the Abel–Jacobi image of the Ceresa cycle ${W_k-W_k^-}$ , where W _k is the image of the kth symmetric product of a curve X on its Jacobian variety. For the Fermat curve of degree N, we express it in terms of special values of generalized hypergeometric functions and give a criterion for the non-vanishing of ${W_k-W_k^-}$ modulo algebraic equivalence, which is verified numerically for some N and k.     

Phase-transfer reactions catalyzed by polymer-supported crown ethers

Polymer-supported crown ethers were prepared from chloromethylated or ω-bromoalkylated polystyrene resins and hydroxymethylbenzo-18-crown-6 and 15- or 18-membered monoazacrown ethers. Effects of the cavity size of crown ethers, the degree of crosslinking, the degree of ring substitution, particle size, spacer chains, and solvents on the activity of the polymer-supported crown ethers in the reaction of 1-chloro- or 1-bromo-octane with aqueous NaI or KI were investigated and mechanisms of the reaction were discussed in terms of mass transfer, intraparticle diffusion, and intrinsic reactivity.     

A new algorithm for surface tension model in moving particle methods

A new algorithm for the surface tension model was developed for moving particle methods. The algorithm is based on the link‐list search algorithm and the continuum surface tension (CST) model. The developed algorithm with the CST model was implemented to a kind of moving particle approach, the finite volume particle (FVP) method. The FVP method with the new algorithm was tested by oscillatory behaviour of a two‐dimensional droplet. The oscillatory period agrees well with analytical one, and the transient shape of the droplet is also in good agreement with that obtained by other numerical methods. The droplet impact on a liquid surface was also studied using the new algorithm. The deposition and splashing phenomena were clearly reproduced. Simulated spread radius of the splashing phenomena was consistent with a power law. Copyright © 2007 John Wiley & Sons, Ltd.     

Pulse radiolysis study of formation of poly(4-vinylbiphenyl) anions in 2-methyltetrahydrofuran solution at 100–120 K

The reactions of poly(4-vinylbiphenyl) (denoted as PVB) polymers and biphenyl molecules with solvated electrons in the 2-methyltetrahydrofuran (MTHF) solvent have been studied at 100–120 K by electron-pulse radiolysis. The formation of PVB polymer anions as well as biphenyl anions was observed by the electron-pulse irradiation of the MTHF-PVB(or biphenyl) solution. The anions are formed by two processes; a rapid formation during the pulse irradiation (<20 ns) and a slow formation after the pulse irradiation. The slow formation is due to a diffusion-controlled reaction between solutes, such as PVB and biphenyl, and solvated electrons. It was found that the reaction efficiency, expressed in monomer unit, of PVB polymers is 1/27 of that of biphenyl molecules. The reaction radius for the electron capture reaction of PVB polymers is estimated as 200–370 A, which is much larger than the gyration radius (107 A) of polymer coils in MTHF solution.     

UV-Vis spectroscopic study on effects of pressure for adsorption ofp-nitrotoluene at liquid-solid interface

The behavior ofp-nitrotoluene adsorbed at zeolite/n-heptane interface has been investigated by the electronic spectroscopy under pressure up to 300 MPa. The uv-vis absorption bands of adsorbedp-nitrotoluene were deconvoluted into ones for the species adsorbed on the cation sites, and one for that on the pore wall of zeolite. The peak of adsorbed species on the cation site red-shifted by 20–80 nm from the position of the same species in the liquid phase, and their magnitudes of shift depended on the strength of electric field generated by the cation in zeolites. The peak intensities of adsorbed species on the cation site were enhanced but these or the pore wall site were reduced with the increase in pressure, suggesting that a part ofp-nitroluene molecules on the pore wall site desorbed and the adsorption on the cation site was enhanced by compression. The pressure dependence of peak intensity indicated that the behavior of this adsorption system was strongly governed by the solvation structure of the adsorbate in the zeolite pore. In particular, it was found that the adsorption of solvent molecules on the cation site strongly affected the volume change of the adsorption system.     

Bismuth‐ and Hafnium‐Catalyzed Hydroamination of Vinyl Arenes with Sulfonamides,Carbamates, and Carboxamides

Catalytic intermolecular hydroamination of vinyl arenes is described. Our initial investigation revealed that a Bi(OTf)₃/[Cu(CH₃CN)₄]PF₆ system previously developed for catalytic intermolecular hydroamination of 1,3‐dienes was suitable for hydroamination of a styrene with sulfonamides, but the substrate generality of this system was unsatisfactory. Several metals were screened to expand the substrate scope, and a new Hf(OTf)₄/[Cu(CH₃CN)₄]PF₆ system was determined to be highly suitable. The combination of Hf(OTf)₄ and [Cu(CH₃CN)₄]PF₆ efficiently promoted the hydroamination of various vinyl arenes, including less‐reactive vinyl arenes with electron‐withdrawing groups. This strategy was applied to sulfonamides, carbamates, and carboxamides, and products were obtained in up to 99 % yield with 0.3–10 mol % catalyst loading.     

Characterization of cryptic plasmids from marine cyanobacteria and construction of a hybrid plasmid potentially capable of transformation of marine cyanobacterium,Synechococcus sp., and its transformation

Applied Biochemistry and Biotechnology - Among forty strains of marine cyanobacteria isolated in our laboratory, five strains had 1–3 different plasmids. The unicellular marine...