Generation of 10- microJ coherent extreme-ultraviolet light by use of high-order harmonics

We demonstrate the generation of 10-microJ coherent extreme-ultraviolet (XUV) light at wavelengths from 73.6 to 42.6 nm, using high-order harmonics. The peak power of this coherent XUV light is estimated to be 0.13 GW at 62.3 nm, and the peak brightness achieved was 3x10(28) photons/(mm(2)mrad(2)s) . To our knowledge, this XUV energy is the highest value achieved with high-order harmonics.     

Synthesis of polycyclic compounds utilizing the nickel-catalysed alkynylstannylation of 1,2-dienes

Polycyclic compounds having linearly-fused six-membered rings can be readily prepared by various modes of cyclization from dienediynes, which were synthesized through the nickel-catalysed alkynylstannylation of 1,2-dienes followed by the palladium-catalysed oxidative homocoupling of the resulting alkenylstannanes.     

First determination of the absolute stereochemistry of a naturally occurring 1,1'-biphenanthrene, (--)-blestriarene C,and its unexpected photoracemization

A naturally occurring 1,1'-biphenanthrene, blestriarene C, was prepared and its absolute stereochemistry was determined to be Sa-(-) by an empirical method, during which the compound was found to undergo rapid photoracemization even under ambient light exposure.     

Reflection high-energy electron diffraction real-time monitoring of an etch process implemented in molecular beam epitaxy technology: hydrogen chloride versus GaAs(001) epilayers

Received: 13 November 1997/Accepted: 19 January 1998     

Anionic polymerization of methyl methacrylate initiated with lithium diphenylamide (Ph2NLi) in the presence of divalent transition metal halide

Anionic polymerization of methyl methacrylate (MMA) in the presence of divalent transition metal halide (MX₂ = FeBr₂, MnCl₂, CoCl₂, NiBr₂) was investigated. Initiating systems with various combinations of MX₂, lithium diphenylamide (Ph₂NLi), and organolithium (RLi, where R = nBu, Me) were effective to giving a high yield of poly(methyl methacrylate)s (PMMAs) at ?78 °C in toluene. The tacticity of the resulting PMMAs was highly dependent on the combination of the reagents used for the generation of the initiating systems within a syndiotactic (rr = 59%) to isotactic (mm = 65%) range. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 31–37, 2004     

Direct vinylogous Mannich-type reactions via ring opening and rearrangement of vinyloxiranes

[reaction: see text] The first synthetic application of 2-methyl-2-vinyloxirane as a masked dienolate has been successfully demonstrated in the direct vinylogous Mannich-type reaction with an alpha-imino ester as an electrophile. The Mannich adduct was a useful intermediate en route to cis-5-substituted pipecolinic acid ethyl ester under simple hydrogenation conditions.     

Stability of stationary interfaces of binary-tree type

We consider the curvature-driven motion of an interface on a bounded domain that contacts with the boundary at the right angle and has triple junctions with prescribed angles. We derive a linearized system at a stationary interface, and obtain a characteristic function whose zeros correspond to the eigenvalues of the linearized operator. From the characteristic function, it is shown that the unstable dimension is not relevant to the topology of the stationary interface but depends mainly on the curvature of the boundary.Received: 8 December 2003, Accepted: 5 April 2004, Published online: 16 July 2004     

A p-phosphinophenolate ligand for the palladium-catalysed arylation of alkenes

A triphenylphosphine having a strong electron-donating group, an oxyanion, at the para position of one of the benzene rings was found to show much higher efficiency compared with other structurally related triarylphosphines in the palladium-catalysed arylation of alkenes.     

Enhanced responses in matrix-assisted laser desorption/ionization mass spectrometry of peptides derivatized with arginine via a C-terminal oxazolone

We have developed a novel method for enhancing the response of a peptide in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) by activating the C-terminal carboxyl group through an oxazolone with which is coupled an amine containing a functional group to help ionize the peptide. The reactions consist of dehydration with acetic anhydride to give an oxazolone, followed by aminolysis with an appropriate amino acid derivative such as arginine methyl ester. The MALDI signal of Ac-Tyr-Gly-Gly-Phe-Leu-Arg-OMe, thus converted from leucine-enkephalin, was detected while completely excluding the responses of arginine-deficient peptides coexisting in the reaction mixture. Some less intense peaks corresponding to a few sequential degradation products, also terminated with the arginine derivative, were also observed. The side-chain groups potentially that are reactive were conveniently protected by acetylation simultaneous with the C-terminal activation, and those that remained unprotected were reduced to virtually negligible proportions when the reaction was conducted in a peptide solution of concentration less than 1 mM. The greatly increased responses of such arginine-terminated peptides could possibly be exploited to discern the C-terminal tryptic peptide of a protein that is otherwise almost insensitive to MALDI-MS in general. The simplicity of the post-source decay spectrum of enkephalin derivatized by arginine methyl ester characteristically accentuated z- and b-type ions, and this should facilitate sequencing of such derivatized peptides. Remaining problems with practical applications of this approach are discussed.