Frequency measuring system using mirror gap stabilized Fabry-Perot interferometer

The mirror gap of a Fabry-Perot interferometer was stabilized with two laser diodes; one locked to the line frequency 385,243,555.14445 MHz of the F=3<--1 in 5D(3/2)<--5S(1/2) (87Rb) and the other to the 385,284,566.3663 MHz of the F=4<--2 in 5D(5/2)<--5S(1/2) (87Rb) [Opt. Commun. 102 (1993) 432]. The length of the mirror gap was adjusted to generate the zero-cross points simultaneously at both of the two line positions. The fringe signals obtained from an interferometer thus stabilized can be used as frequency markers having accuracies of the order of 10(10) depending on the finesse of the interferometer used. Based on measurement using Cs D1 hyperfine lines reported by Udem et al. [Phys. Rev. Lett. 82 (1999) 3568], the uncertainty of markers in the region 50 THz apart from the reference lines is +/- 5 MHz.     

Heteroatom-guided torquoselective olefination of alpha-oxy and alpha-amino ketones via ynolates

Ynolates were found to react with alpha-alkoxy-, alpha-siloxy-, and alpha-aryloxyketones at room temperature to afford tetrasubstituted olefins with high Z selectivity. Since the geometrical selectivity was determined in the ring opening of the beta-lactone enolate intermediates, the torquoselectivity was controlled by the ethereal oxygen atoms. From experimental and theoretical studies, the high Z selectivity is induced by orbital and steric interactions rather than by chelation. In a similar manner, alpha-dialkylamino ketones provided olefins with excellent Z selectivity. These products can be easily converted into multisubstituted butenolides and gamma-butyrolactams in good yield.     

Synthesis and self-aggregation of cyclic alkynes containing helicene

[structure: see text]. All stereoisomers of a cyclic alkyne containing three helicene units, 1,12-dimethylbenzo[c]phenanthrene, are synthesized using a building block. Isomeric [3 + 3]cycloalkynes aggregate in organic solvents. Vapor pressure osmometry reveals dimer formation of (M,M,M)-[3 + 3]cycloalkynes in chloroform and benzene at concentrations above 2 mM. No higher aggregation is observed. The chirality of helicenes plays an important role in self-aggregation, and diastereomeric (M,P,M)-[3 + 3]cycloalkyne forms a dimer only above 15 mM. Aggregation of racemic (M,M,M)-[3 + 3]cycloalkyne or (M,P,M)-[3 + 3]cycloalkyne is much weaker than that of a single enantiomer.     

Combinatorial synthesis of MUC1 glycopeptides: polymer blotting facilitates chemical and enzymatic synthesis of highly complicated mucin glycopeptides

The chemoselective polymer blotting method allows for rapid and efficient synthesis of glycopeptides based on a "catch and release" strategy between solid-phase and water-soluble polymer supports. We have developed a heterobifunctional linker sensitive to glutamic acid specific protease (BLase). The general procedure consists of five steps, namely (i) the solid-phase synthesis of glycopeptide containing BLase sensitive linker, (ii) subsequent deprotections and the release of the glycopeptide from the resin, (iii) chemoselective blotting of the glycopeptide intermediates in the presence of water-soluble polymers with oxylamino functional groups, (iv) sugar elongations using glycosyltransferases, and (v) the release of target glycopeptides from the polymer platform by selective BLase promoted hydrolysis. The combined use of the solid-phase chemical syntheses of peptides and the enzymatic syntheses of carbohydrates on water-soluble polymers would greatly contribute to the production of complicated glycopeptide libraries, thereby enhancing applicative research. We report here a high-throughput synthetic system for the various types of MUC1 glycopeptides exhibiting a variety of sugar moieties. It is our belief that this concept will become part of the entrenched repertoire for the synthesis of biologically important glycopeptides on the basis of glycosyltransferase reactions in automated and combinatorial syntheses.     

Shape-persistent cyclyne-type azamacrocycles: synthesis, unusual light-emitting characteristics, and specific recognition of the Sb(V) ion

Simple members of arene-azaarenecyclynes as a novel family of geometrically-controlled and shape-persistent azamacrocycles have been synthesized. Noteworthy is the specific recognition function for Sb(V). The synthesized azamacrocycles, in particular the Sb(V) complex, have unusually strong light-emitting property.     

Reduction of acetophenone using supercritical 2-propanol: the substituent effect and the deuterium kinetic isotope effect

The reductions of several substituted acetophenones using supercritical 2-propanol were carried out to estimate the Hammett's reaction constant (ρ=0.33). Also, the reduction of acetophenone using supercritical deuteriated 2-propanol was carried out to determine the rate-determining step. The kinetic isotope effects were observed in the reduction using 2-deuterio-2-propanol (k_H/k_D=1.6) and O-deuterio-2-propanol (k_H/k_D=2.0). These findings suggest that the reaction proceeds via a cyclic transition state between acetophenone and 2-propanol similar to that of the Meerwein-Ponndorf-Verley reduction.     

Asymmetric 1,4-addition of alkenylzirconium reagents to α,β-unsaturated ketones catalyzed by chiral rhodium complexes

Highly enantioselective 1,4-addition of alkenylzirconocene chlorides to α,β-enones was found to be catalyzed by a chiral rhodium complex generated from [Rh(cod)(MeCN)₂]BF₄ and (S)-BINAP. The reaction can be applied to either cyclic or acyclic enones and the optical yield was up to 99% ee. The reaction mechanism would involve the transmetalation between the alkenylzirconocene chloride and the rhodium complex to give the alkenylrhodium species as a key intermediate.     

Copolymerization of optically active N-bornylmaleimide with vinyl monomers

Optically active N-bornylmaleimide (NBMI) was copolymerized with styrene, methyl methacrylate, and vinylidene chloride with a free-radical catalyst to obtain optically active copolymers. The monomer reactivity ratios for the radical copolymerization of NBMI (M₂) with styrene, methyl methacrylate, and vinylidene chloride were: ST-NBMI, r₁ = 0.13, r₂ = 0.05; MMA-NBMI, r₁ = 2.02, r₂ = 0.16; VCl₂-NBMI, r₁ = 1.15, r₂ = 0.47. The Q-e values for NBMI were Q₂ = 0.48 and e₂ = +1.47. The specific rotation and optical rotatory dispersion of these copolymers were measured. The correlation between the specific rotation and composition of these copolymers was not linear. The value of λ_c for each copolymer was independent of the copolymer composition and the comonomer, being 260 mμ for the St-NBMI system, 262 mμ for the MMA-system, and 260 mμ for the VCl₂-NBMI system. The effects of solvents and temperature on the specific rotation of these copolymers were investigated.     

Formation of pyrazine derivatives from D-glucosamine and their deoxyribonucleic acid (DNA) strand breakage activity

Two pyrazine derivatives [fructosazine (3) and deoxyfructosazine (6)] were simultaneously formed in a solution of D-glucosamine hydrochloride under various conditions. They showed deoxyribonucleic acid (DNA) strand breakage activity in plasmid pBR322 comparable to that of D-glucosamine. The DNA strand breakage by fructosazine (3) was stimulated by Cu2+.     

Effect of explicit cationic size and valence constraints on the phase stability of 1:2 B-site-ordered perovskite ruthenates

The related parameters of cation size and valence that control the crystallization of Sr(3)CaRu(2)O(9) into a 1:2 B-site-ordered perovskite structure were explored by cationic substitution at the strontium and calcium sites and by the application of high pressure. At ambient pressures, Sr(3)MRu(2)O(9) stoichiometries yield multiphasic mixtures for M = Ni(2+), Mg(2+), and Y(3+), whereas pseudocubic perovskites result for M = Cu(2+) and Zn(2+). For A-site substitutions, an ordered perovskite structure results for Sr(3-x)Ca(x)CaRu(2)O(9), with 0 相似文献