Role of the K 1 Meson in K 0 Photoproduction off the Deuteron

Neutral kaon photoproduction off the nucleon and deuteron has been reinvestigated by utilizing the new experimental data on both targets. An isobar model for elementary operator and impulse approximation for the reaction on the deuteron have been used. The available free parameters in the elementary model have been extracted from both elementary and deuteron data. In contrast to the elementary reaction, fitting the deuteron data requires an inclusion of weighting factor. The result indicates that the angular distribution of the elementary ${K^0\Lambda}$ process does not show backward peaking behavior.     

Synthesis of 2,4,6-trisubstituted chiral piperidines and (-)-dendroprimine by one-pot asymmetric azaelectrocyclization protocol

[reaction: see text] Stereocontrolled synthesis of 2,4,6-trisubstituted piperidine diastereomers has been realized from common intermediates, obtained by a one-pot azaelectrocyclization protocol. Based on the method, the asymmetric synthesis of an indolizidine alkaloid, (-)-dendroprimine, was achieved.     

Development of dual gradient column in liquid chromatography

The dual gradient column, in which both the chemical property of the stationary phase and the flow velocity in the mobile phase are heterogeneous longitudinally along the column, is developed to obtain the mobile phase gradient-like elution in an isocratic condition. Here, the step-wise dual gradient columns were prepared by connecting an inlet column (I.D. 50 microm, packed with ODS) serially to an outlet column (I.D. 100-200 microm, packed with the mixture of ODS and C1 [9:1]). The retention behavior of alkylbenzenes was able to be controlled in the dual gradient column depending on the variation in the flow velocity. Moreover, the change in retention behavior induced by the flow velocity variation for the dual gradient columns was quite different from that by the variation in organic modifier content of the mobile phase in isocratic elution for a single gradient column and can induce the similar effect with an ordinary gradient elution in a mobile phase composition.     

Asymmetric total synthesis of antileukemic sesquiterpene (+)-ivalin

The one-pot double alkylation reaction of a chiral α,β-unsaturated imine (6) with isopropenyl Grignard reagent followed by methyl iodide has been shown to proceed highly asymmetrically. Subsequent stereoselective transformation of the derived adduct (10) has culminated in a first asymmetric total synthesis of the optically pure eudesmane sesquiterpene (+)-ivalin (1).     

Negative ENDOR study of the radiation damage in triglycine sulphate

An ENDOR study of irradiated TGS crystals was conducted, and it was found that in the ferroelectric phase the splitting of a proton signal decreased with increasing doses of irradiation. This decrease was interpreted in terms of a reduction in a parameter $\text{σ }\text{ΔE°}\text{2Γ}$, where ΔE° is the energy difference between the two minima of the effective tunneling potential for the proton and Γ is the exchange (tunneling) integral. Furthermore, it was shown that the reduction in σ originates predominantly from the paramagnetic centers resulting from irradiation.     

Vis‐sensitive photopolymer containing vinyl ether compound and pyrromethene dye

A visible light(vis)‐sensitive photoresist based on the concept of chemical amplification was developed utilizing poly(p‐hydroxystyrene) (PHS), 2,2‐bis[4‐(2‐(vinyloxy)‐ethoxy)phenyl]propane (BPA‐DEVE) as a crosslinking agent, N‐trifluoromethylsulfonyloxy‐1,8‐naphthalimide (NIT) as a photoacid generator (PAG) and pyrromethene dyes such as 1,3,5,7,9‐pentamethylbipyrromethene difluoroborate (PRH) and 2,8‐diethyl‐1,3,5,7,9‐pentamethylbipyrromethene difluoroborate (PRE) and 3,3′‐carbonylbis(7,7′‐diethylaminocoumarin) (KCD). On irradiation with an argon ion laser, the photopolymer comprising PRH and PRE exhibited a high sensitivity of 65 and 46 mJ cm^?2, respectively. It is suggested that the sensitization mechanism of the pyrromethene dye/PAG system involves singlet electron transfer. The sensitivity of the photoresist increased with the decreasing molecular weight of PHS because of the high dissolution rate. Copyright © 2002 John Wiley & Sons, Ltd.     

Enantioselective esterification of prochiral phosphonate pendants of a polyphenylacetylene assisted by macromolecular helicity: storage of a dynamic macromolecular helicity memory

A poly(phenylacetylene) bearing a phosphonic acid monoethyl ester as the pendant forms a one-handed helical structure induced by an optically active amine, and this helicity can be "memorized"after the amine is replaced by achiral diamines. The helicity memory lasts for an extremely long time but spontaneously disappears after the achiral diamines are removed by a stronger acid, indicating the dynamic nature of the helicity memory. Here we report that such a dynamic memory could be "stored" after the pendant was converted to its methyl ester with diazomethane, resulting in the generation of a phosphorus stereogenic center with optical activity. The esterification enantioselectively proceeded through chirality transfer from the induced helical conformation or the helicity memory of the polyacetylene backbone. Although the enantioselectivity was low, the pendant chirality was significantly amplified in the polymer backbone at low temperatures, resulting in higher optical activity as an excess single-handed helix than that expected from the enantiomeric excess of the pendants.     

Negative‐working photoresist of methacrylate polymers based on the transesterification of the 2‐hydroxyethyl group in the presence of an acid

This article reports a novel crosslinking functionality of the 2‐hydroxyethyl methacrylate unit (HEMA) in the presence of an acid. The polymeric compositions, consisting of a polymer containing the HEMA unit and a photoacid generator, were insolubilized in an aqueous base developer on exposure to UV light and a successive baking process to provide a negative‐working photoresist. A series of poly(benzyl methacrylate‐co‐methacrylic acid‐co‐2‐hydroxyethyl methacrylate) terpolymers with various contents of HEMA were prepared to elucidate the photopolymeric characteristics. The polymer behavior in films was examined by a comparison of the photosensitivity and IR spectroscopic method. Experiments with a model compound were also carried out. On the basis of the results, we found that the resist was insolubilized by crosslinking through the transesterification of HEMA segments due to acid generated from the photoacid generator and subsequent heating. The advantage of using the 2‐hydroxyethyl group is that in the terpolymer, the HEMA unit is transparent at a short‐wavelength region and is a promising crosslinking unit for ArF lithographic photoresists. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1858–1867, 2002     

Capillary high-performance liquid chromatography/electrospray ion trap time-of-flight mass spectrometry using a novel nanoflow gradient generator

A type of high-performance liquid chromatography (HPLC) based on a novel nanoflow gradient generator (Asymptotic-Trace-10-Port-Valve (AT10PV) nanoGR generator) was developed and coupled with an electrospray ion trap time-of-flight mass spectrometer (ESI-IT-TOF MS). Stability of the nanoflow GR HPLC system was tested at flow rates of 20 and 50 nL/min by using a nanoflow meter. Average flow rates in a 2-h run were 51.2 nL/min with RSD 0.7% and 21.0 nL/min with RSD 1.8%. Repeatability of analysis of the nanoHPLC/ESI-IT-TOF MS system was also tested by injecting 1.0 microL of trypsin digested bovine serum albumin (BSA) (100 fmol) into a monolithic silica-ODS column (30 microm i.d., 150 mm in length) through a packed silica-ODS trapping column (particle size 5 microm, 150 microm i.d., 10 mm in length). At a flow rate of 50 nL/min, the result demonstrated a reasonably good repeatability of peak retention times (RSD: 0.32-1.1%) and base-ion peak areas (RSD: 4.4-6.6%).