Second-order nonlinear optical properties from poled silicate channel-waveguide

Thin film waveguides of germanosilicate glass are fabricated byrf-sputtering. Second-order nonlinearity ofd ₃₃=3.2 pm/V is obtained from electrically poled film, and the lifetime of the nonlinearity is found to be310 years. The poled channel-waveguide is prepared and the Cerenkov-type phase-matched frequency doubling is successfully observed.     

On the space curves with the same image under the gauss maps

From an irreducible complete immersed curveX in a projective space ? other than a line, one obtains a curveX ^′ in a Graasmann manifoldG of lines in ? that is the image ofX under the Gauss map, which is defined by the embedded tangents ofX. The main result of this article clarifies in case of positive characteristic what curvesX have the sameX′: It is shown thatX is uniquely determined byX′ ifX, or equivalentlyX′, has geometric genus at least two, and that for curvesX ₁ andX ₂ withX ₁ ≠X ₂ in ?, ifX′₁ =X′₂ inG and eitherX ₁ orX ₂ is reflexive, then bothX ₁ andX ₂ are rational or supersingular elliptic; moreover, examples of smoothX ₁ andX ₂ in that case are given.     

Michael addition reactions of acetoacetates and malonates with acrylates in water under strongly alkaline conditions

Michael addition reactions of acetoacetates and malonates with acrylates in a 5 M KOH aqueous solution without using any other catalysts are described. When they are either tert-butyl or benzyl esters, the reaction proceeded very rapidly to afford moderate to high yields of the corresponding bis-Michael adducts that are unexpectedly stable under these conditions.     

Synthesis of 3-epi-6,7-dideoxyxestobergsterol A

3-Epi-6,7-dideoxyxestobergsterol A (2), an analogue of xestobergsterol A, has been synthesized from dehydroepiandrosterone (3) in 15 steps. The key synthetic intermediate, 15beta,16alpha-dioxypregn-17(20)E-ene derivative 8, was prepared from the corresponding 15beta,16beta-epoxide 6 by treating with acetic acid and titanium tetraisopropoxide. The 23-oxo side chain was constructed stereoselectively by orthoester Claisen rearrangement of 8 followed by introduction of an isobutyl group. Basic treatment of the 15,23-diketone 12 followed by deprotection gave the title compound 2.     

pH-regulated formation of amyloid-like beta-sheet assemblies from polyglutamate grafted polyallylamine

A novel artificial protein with simple primary structure, poly(gamma-methyl-L-glutamate)-grafted polyallylamine, has been prepared and the resultant peptide has shown a unique property of pH-regulated conformation and morphology.     

Efficient synthesis of isoplagiochin D, a macrocyclic bis(bibenzyls), by utilizing an intramolecular Suzuki-Miyaura reaction

Isoplagiochin D, a highly strained macrocyclic bis(bibenzyls) with two biaryl units isolated from the liverwort Pladiochila fruticosa, was prepared in 10.6% overall yield for the 11 steps by an efficient synthetic approach involving the construction of two bibenzyl and one biaryl units using Horner-Wadsworth-Emmons and Suzuki-Miyaura protocols.     

Effects of dipole moment, linkers, and chromophores at side chains on long-range electron transfer through helical peptides

Octadecapeptides carrying a ferrocene moiety at the molecular terminal were self-assembled on gold, and long-range electron transfer from the ferrocene moiety to gold was investigated by electrochemical methods. Effects on electron transfer of dipole moment of helical peptides, linkers connecting the peptide to gold, and chromophores introduced into the side chains were discussed. Cyclic voltammetry of the monolayers in an aqueous solution revealed that long-range electron transfer over 40 A occurred along the peptide molecule. Chronoamperometry showed that the long-range electron transfer should be ascribed to a hopping mechanism with use of amide groups as hopping sites. Electron transfer through the long peptide was not significantly accelerated by the dipole moment. However, the linker remarkably affected electron transfer depending on whether it was a methylene chain or a phenylene group, suggesting that local electron transfer between gold and the peptides should be the slowest step to determine the overall rate. Pyrenyl groups introduced into the side chains in the middle of the peptide molecule did not noticeably change electron transfer, probably because pyrenyl groups were too distant to allow direct electron transfer between them. Electrostatic potential profiles across the peptide monolayers were also calculated to explain reasonably the several interesting features in the present peptide systems.     

2,2′-Isopropylidenebis[(4S,5R)-4,5-di(2-naphthyl)-2-oxazoline] ligand for asymmetric cyclization-carbonylation of meso-2-alkyl-2-propargylcyclohexane-1,3-diols

The oxidative cyclization-carbonylation of meso-2-alkyl-2-propargylcyclohexane-1,3-diols mediated by Pd(II) with chiral bisoxazoline (box ligand) afforded bicyclic-β-alkoxyacrylates. Based on a ligand screening, 2,2′-isopropylidenebis[(4S,5R)-4,5-di(2-naphthyl)-2-oxazoline] ligand has been developed. The products with a chiral quaternary carbon were obtained in 71-100% yields with 85-95% ee.