Preparation of perfluorocyclopentenylmetal species and their cross-coupling reaction with electrophiles—Remarkable accesses to versatile perfluorocyclopentene derivatives

On treating perfluorocyclopentene with bis(tributylstannyl)cyanocuprate in THF at −78 °C for 1 h, perfluorocyclopentenylstannane was obtained in good yield. The reaction of the fluorinated vinylstannane with n-BuLi in THF at −78 °C for 1 h, followed by addition of carbonyl compounds, gave the corresponding allyl alcohols in good yields. On the other hand, Pd(0)-catalyzed cross-coupling reaction of perfluorocyclopentenylstannane with benzyl chloroformate in THF at reflux temperature for 2 h proceeded smoothly to form the decarbonated coupling product in high yield.     

Post-column derivatization capillary electrochromatography for detection of biogenic amines in tuna-meat

A system to perform post-column derivatization capillary electrochromatography (CEC) was developed for the first time. The system mainly included a 4-microm (O.D.) silica packed column (200 mm effective length x 0.1 mm inner diameter I.D.) with micro-magnetic particles (MMPs) frits, a T-junction connector, an in-line fluorescence detector and a high-voltage power supply. The system was evaluated by using histamine (HA) as a standard biogenic amine for this study. A 5 microM HA solution was loaded at the anodic site of the capillary column by applying 3 kV for 5s. Then, HA was electrophoretically eluted with a 20mM phosphate buffer (pH 7) by applying 3 kV, and was derivatized with 3mM o-phthalaldehyde (OPA)/N-acetylcysteine (NAC) in 100 mM borate (pH 10), which was continuously delivered through the reagent-loading capillary tube by gravity into the T-junction connector. HA derivative was finally detected with the in-line fluorescence detector (lambda(Ex)=340 nm, lambda(Em)=450 nm) at 9.7 min after sample loading. To test the utility of this system, it was next employed for its ability to detect the presence of HA and other kinds of biogenic amines, including cadaverine (Cad), spermidine (Spm) and tyramine (Tyr) in tuna-meat, once the validity of the method had been confirmed.     

An efficient transformation of cyclic ene-carbamates into omega-(N-formylamino)carboxylic acids by ruthenium tetroxide oxidation

The ruthenium tetroxide (RuO(4)) oxidation of cyclic ene-carbamates resulted in the endo-cyclic carbon-carbon double bond cleavage to afford the corresponding omega-(N-formylamino)carboxylic acids in good yields. Substituted cyclic ene-carbamates derived from (3R)-3-hydroxypiperidine hydrochloride were converted into the N-Boc 4-aminobutyric acids by utilization of the RuO(4) oxidation as the key step, which were further transformed into (3R)-4-amino-3-hydroxybutyric acid, an important key intermediate for the synthesis of L-carnitine.     

Do specular highlights and the daylight locus act as cues for estimating illumination color from a single object?

Optical Review - Specular highlights on the surface of an object can serve as cues for estimating illumination color, because highlights on many objects directly reflect illumination colors. In...     

Effect of dielectric properties of solvents on the quality factor for a beyond 900 MHz cryogenic probe model

A previous report by Kelly et al. [J. Am. Chem. Soc. 124 (2002) 12013] indicated that the ionic conductivity of aqueous solution produces a significant contribution to the sensitivity loss in high-resolution NMR equipped with a cryogenically cooled probe. The loss in a sample solution contains two contributions: one from the ionic conductivity and the other from the dielectric loss; the latter is especially important at high frequencies such as above 900 MHz. Here, we investigated the effect of the dielectric conductivity on the quality factor of a 930 MHz cryogenic probe model; in particular, it deals with the ionic aqueous solutions and organic solvents commonly used for NMR in biological research and the chemistry of natural compounds. The sample quality factor, Qs, at first increases with the real part of the relative dielectric permittivity epsilon' and then saturates. In the case of polar organic solvents, the transverse electric field on the sample decreases with epsilon', resulting in an increase of Qs. In the case of non-polar organic solvents, the dielectric conductivity is so small that the gradient of the increase is steep, resulting in much larger Qs though the epsilon' is small. The effect of the transverse electric field is negligible if the epsilon' becomes large, thus the loss for ionic aqueous solution is mainly governed by a loop current induced in the sample solution. As the induced electromotive force is independent of the epsilon', the Qs is saturated at high values of epsilon'. Based on the Qs obtained with the cryogenic probe model, the sensitivity for the cryogenic probe is expected to be as follows: the loss in sensitivity by loading water is more than 66%, i.e., the effect of the dielectric conductivity of water is remarkable at high frequencies; polar organic solvent suffers much larger losses, which is due to the enhancement of the effective sample resistance by the effect of epsilon'; a non-polar organic solvent is nearly free of the sensitivity loss as the dielectric conductivity is negligible; the reverse micelle behaves similarly.     

A facile and versatile preparation of bilindiones and biladienones from tetraarylporphyrins

Bilindiones and biladienones carrying aryl groups at the meso positions were prepared using coupled oxidation reactions of iron tetraarylporphyrins in 20-63% yield.     

Surface-active particles with microstructured surfaces

Interfaces adsorbing solid particles have recently attracted great attentions in the field of materials science, because they are useful as templates of well-ordered particle arrays or of microstructured hollow spheres. The solid particles are adsorbed at the interfaces and form self-assembled structures when the particles have suitable wettability to both fluids. Here, we show theoretically how the microstructure on the particle surface affects their adsorption properties. The physical properties of the interface adsorbing a particle will be described with consideration for surface area magnification due to the microstructure. The microstructure on the surface changes drastically the wettability and the equilibrium position of the adsorbed particle and prevents the particle from adsorption at the interface. The range of the interfacial tensions at which the particle is adsorbed becomes narrower with the increase of the magnification. On the other hand, the particle which is partially covered with the microstructured surface is adsorbed firmly at the interface in an oriented state. We should consider not only the interfacial tensions but also the surface structure to control the adsorption behavior of the particle.     

Comparative Investigation on the Concentration-Dependences of the Half-Band Widths of Infrared Absorption and Raman Bands

It is demonstrated that the fashions of the concentration-dependences of half-band widths are markedly different between the corresponding bands in i.r. absorption and Raman spectra when the i.r. absorption intensities of the bands are extremely large. On the other hand, when the i.r. intensities are not so great, the similar behaviour is observed for the changes in the half-band widths. In this study, these phenomena have been discussed in terms of the vibrational relaxation of resonance type and the local field effect.