Preparation of enantiomerically pure (R)-2-butyryloxymethylglycidol by lipase-catalyzed asymmetric hydrolysis

Optically active epoxy alcohol, (R)-2-butyryloxymethylglycidol3 which is the precursor of a tert-alcohol chiral building block was obtained in high enantiomeric purity, 98.7% e.e., by lipase-catalyzed asymmetric hydrolysis using a phosphate buffer and organic co-solvent system in 95% of chemical yield.     

Emergent rotational symmetries in disordered magnetic domain patterns

Uniaxial systems often form labyrinthine domains that exhibit short-range order but are macroscopically isotropic and would not be expected to exhibit precise symmetries. However, their underlying frustration results in a multitude of metastable configurations of comparable energy, and driving such a system externally might lead to pattern formation. We find that soft x-ray speckle diffraction patterns of the labyrinthine domains in CoPd/IrMn heterostructures reveal a diverse array of hidden rotational symmetries about the magnetization axis, thereby suggesting an unusual form of emergent order in an otherwise disordered system. These symmetries depend on applied magnetic field, magnetization history, and scattering wave vector. Maps of rotational symmetry exhibit intriguing structures that can be controlled by manipulating the applied magnetic field in concert with the exchange bias condition.     

Using ionic strength to control liquid-ordered/liquid-disordered separation

In this Letter, we will show that liquid-ordered/liquid-disordered separation can be controlled with ionic strength. Using this observation, a robust method was developed for creating visible, by fluorescence microscopy, liquid-ordered domains in supported lipid bilayers. The details of the method will be discussed.     

Synthesis of both the enantiomers of endo-brevicomin,the aggregation pheromone of Dryocoetes autographus

(1R,5S,7S)-(+)-endo-Brevicomin (7-ethyl-5-methyl-6,8-dioxabicyclo[3.2.1]octane) and its (1S,5R),7(R)-(?)-isomer were synthesised employing the Sharpless asymmetric epoxidation as the key-step.     

Regioselectivity and mechanism of dihalocarbene addition to benzocyclopropene

Dihalocarbenes add regioselectively to aryl-substituted benzocyclopropenes to produce dihalobenzocyclobutenes. The regioselectivity of addition is not due to steric effects but depends on the electronic donor or acceptor ability of the substituent. B3LYP/6-31G* calculations show preferential :CCl2 addition to substituted benzocyclopropene through electrophilic attack on the benzocyclopropene pi-system (Ea = 1.1-2.4 kcal/mol) rather than C-C sigma-bond insertion into the cyclopropenyl moiety (Ea = 5-24 kcal/mol). pi-Addition proceeds regioselectively through a single transition state to xylylene intermediates or directly to benzocyclobutene products.     

Electrocatalytic oxidation of formate by [Ni(P(R)2N(R')2)2(CH3CN)]2+ complexes

[Ni(P(R)(2)N(R')(2))(2)(CH(3)CN)](2+) complexes with R = Ph, R' = 4-MeOPh or R = Cy, R' = Ph , and a mixed-ligand [Ni(P(R)(2)N(R')(2))(P(R'(2))N(R'(2)))(CH(3)CN)](2+) with R = Cy, R' = Ph, R' = Ph, have been synthesized and characterized by single-crystal X-ray crystallography. These and previously reported complexes are shown to be electrocatalysts for the oxidation of formate in solution to produce CO(2), protons, and electrons, with rates that are first-order in catalyst and formate at formate concentrations below ～0.04 M (34 equiv). At concentrations above ～0.06 M formate (52 equiv), catalytic rates become nearly independent of formate concentration. For the catalysts studied, maximum observed turnover frequencies vary from <1.1 to 15.8 s(-1) at room temperature, which are the highest rates yet reported for formate oxidation by homogeneous catalysts. These catalysts are the only base-metal electrocatalysts as well as the only homogeneous electrocatalysts reported to date for the oxidation of formate. An acetate complex demonstrating an η(1)-OC(O)CH(3) binding mode to nickel has also been synthesized and characterized by single-crystal X-ray crystallography. Based on this structure and the electrochemical and spectroscopic data, a mechanistic scheme for electrocatalytic formate oxidation is proposed which involves formate binding followed by a rate-limiting proton and two-electron transfer step accompanied by CO(2) liberation. The pendant amines have been demonstrated to be essential for electrocatalysis, as no activity toward formate oxidation was observed for the similar [Ni(depe)(2)](2+) (depe = 1,2-bis(diethylphosphino)ethane) complex.     

The radar system for the exploration of Titan

Summary In the field of the exploration of the Solar System NASA and ESA have jointly planned two cornerstone missions whose aim is the close observation of two largely unknown planetary bodies: Titan (Cassini mission) and comet nuclei (Rosetta mission). Our attention in this paper will be devoted to the first one, however some results of this study can be applied also to the second one. Titan is one of Saturn's moons and is characterized by the presence of a dense atmosphere, opaque for optical sensors. Therefore radar data are the only ones at least theoretically capable of giving relatively detailed informations about the geomorphologic structure of Titan. As a matter of fact the radar cross-section depends on both the dielectric constant of the target by means of the Fresnel reflectivity and on its surface roughness. Moreover if the attenuation is sufficiently low, the radar in principle could be able to detect subsurface discontinuities as well. The above considerations hold true only if a well-suited analytical model accounting for surface backscattering is known. All throughout this paper the radar cross-section of planetary bodies will be evaluated in the case of high-resolution radars. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.     

Sensitivity enhancement of multidimensional NMR experiments by paramagnetic relaxation effects

One of the main goals of NMR method development is to increase the sensitivity of multidimensional NMR experiments or reduce the required acquisition time. In these experiments, more than 80% of the NMR instrument time is spent on the recycle delay, where the instrument idles to wait for the recovery of proton magnetization. In this study, we report a method of using paramagnetic relaxation effects to shorten the recycle delays required in multidimensional NMR experiments of biological macromolecules. This approach significantly reduces the NMR instrument time required. Ni(2+) ion, complexed with the chelating molecule DO2A, is used to decrease the proton T(1) relaxation time of biological macromolecules without the significant line-broadening effects that are associated with most paramagnetic ions. The Ni(DO2A) also significantly decreases the T(1) relaxation time of water, thus providing additional sensitivity gain by eliminating the saturation of labile amide resonances.     

Splitting of magnetic dipole modes in anisotropic TiO2 micro‐spheres

Monocrystalline titanium dioxide (TiO₂) micro‐spheres support two orthogonal magnetic dipole modes at terahertz (THz) frequencies due to strong dielectric anisotropy. For the first time, we experimentally detected the splitting of the first Mie mode in spheres of radii m through near‐field time‐domain THz spectroscopy. By fitting the Fano lineshape model to the experimentally obtained spectra of the electric field detected by the sub‐wavelength aperture probe, we found that the magnetic dipole resonances in TiO₂ spheres have narrow linewidths of only tens of gigahertz. Anisotropic TiO₂ micro‐resonators can be used to enhance the interplay of magnetic and electric dipole resonances in the emerging THz all‐dielectric metamaterial technology.