Stereoselective formation of N-acyliminium ion via chiral N,O-acetal TMS ether and its application to the synthesis of beta-amino acids

[reaction: see text] The highly stereoselective synthesis of beta-amino acids via the chiral 4-phenyloxazolidinone-controlled linear N-acyliminium ion reaction has been achieved by employing chiral N,O-acetal TMS ethers. In addition, the mechanism of the excellent stereochemical outcome has been elucidated. The oxazolidinone auxiliary plays a dual role in stereocontrol: the E/Z geometry control of the N-acyliminium ion induced by an initial stereoselective amide reduction, leading to the chiral N,O-acetal TMS ether, and face control of the nucleophile attack in the N-acyliminium ion reaction.     

Thermal Properties of the Aquadimethylsulfoxide Complexes [Ln(DMSO)n(H2O)m][Mo3S7Br7] where Ln=Pr,Nd, Eu,Tm

Synthesis, X-ray structural investigation, and study of the thermal properties of new aquadimethylsulfoxide complexes [Ln(DMSO)n(H2O)m][Mo3S7 Br7] containing the rare earth metals (Ln=Pr, Nd, Eu, Tm) were performed. In all complexes DMSO is co-ordinated through the O atoms. Thermal transformations of these salts were studied by quasi-equilibrium thermogravimetry a variant of CRTA (Controlled Rate Thermal Analysis) with constant rate of mass loss (0.3 mg min-1); helium flow keeps the partial pressure of self-generated DMSO/H2O atmosphere ~0.01 atm. [Pr(DMSO)6H2O]X where X=[Mo3S7Br7] decomposes with the formation of the intermediate phases Pr(DMSO)5X at 100-190°C and Pr(DMSO)3X at 250-270°C. Thermal decomposition of [Nd(DMSO)6(H2O)X·CH3CN leads to the intermediate phase Nd(DMSO)5X at 200-210°C. [Eu(DMSO)7(H2O)]X forms the intermediate phases Eu(DMSO)6X at 50-150°C and Eu(DMSO)5X at 190-210°C. Thermal decomposition of [Tm(DMSO)6(H2O)]X gives the intermediate phases Tm(DMSO)5X at 170-200°C and Tm(DMSO)4X at 240-250°C. The further decomposition takes place continuously for all phases. This revised version was published online in July 2006 with corrections to the Cover Date.     

Asymmetric total synthesis of bacillariolide III, a marine oxylipin

[reaction: see text] The asymmetric total synthesis of bacillariolide III has been achieved via 15 linear steps in 14.6% overall yield. The key feature of this synthetic route involves the highly stereoselective construction of the vinyl-substituted bicyclic lactone by an intramolecular Pd(0)-catalyzed allylic alkylation and its facile conversion to the hydroxy bicyclic lactone skeleton of bacillariolide III, induced by stereoselective vinylcerium addition to the aldehyde. In addition, the (Z)-pentenoic acid was efficiently introduced by the internal hydroxy group tethered ring-closing metathesis (RCM).     

Methyl Jasmonate Induce Enhanced Production of Soluble Biophenols in PANAX GINSENG Adventitious Roots from Commercial Scale Bioreactors

The contents of soluble biophenols such as protocatechuic, gentisic, vanillic, caffeic, syringic, p-coumaric, ferulic, salicylic, and cinnamic acids were screened and quantified from the adventitious roots of Panax ginseng by HPLC-MS. Control adventitious roots which showed the greatest accumulation of ferulic acid (0.09 mg/g DW) were observed in our experiments. An increase in the total soluble biophenol content of adventitious roots was observed 5 days after treatment with elicitor 200 μM/L methyl jasmonate (MeJa) i.e., 35 to 40 days of inoculation. Among the biophenols investigated, the salicylic acid content was higher (0.44 mg/g DW) in MeJa treated adventitious root culture in the bioreactor. MeJa might apparently increase soluble biophenols production in adventitious roots by enhancing the biosynthesis pathway from phenylalanine to salicylic acid and other simple biophenols. __________ Published in Khimiya Prirodnykh Soedinenii, No. 6, pp. 551–554, November–December, 2005     

Photoinduced refractive-index change in Sm(+2)/Sm(+3) codoped aluminosilicate fiber by irradiation of an Ar-ion laser

A Sm(+2)/Sm(+3) codoped aluminosilicate glass optical fiber was fabricated by use of modified chemical-vapor deposition in conjunction with an aerosol-delivery technique. A permanent index change of 7.6 x 10(-5) was induced in the fiber by irradiation of 1 W of multiline output from an Ar-ion laser. Bleaching of a broad absorption band of Sm(+2) in the visible range was also observed, and it is believed that photoionization of Sm(+2)? Sm(+3)+e plays an important role in the induced photorefractivity.     

Preferential regrowth of indium–tin oxide (ITO) films deposited on GaN (0001) by rf-magnetron sputter

Effects of thermal treatments on the electrical properties and microstructures of indium–tin oxide (ITO)/GaN contacts have been investigated using a rf-magnetron sputter deposition followed by rapid thermal annealing. ITO films annealed at 800 °C revealed Schottky contact characteristics with a barrier height corresponding to ITO’s work function of 4.62 eV. The evolution of electrical properties of ITO/GaN contacts was attributed to the preferential regrowth of In₂O₃ (222)//GaN (0001) with an ideal metal–semiconductor Schottky contact. The feasible use of ITO/GaN as a transparent Schottky contact would be realized by the enhanced regrowth of In₂O₃ at high temperature. Received: 1 September 2000 / Accepted: 15 November 2000 / Published online: 28 February 2001     

Use of capillary electrophoresis with UV detection as a screening method to determine histamine in fish samples.

Histamine levels in fish, extracted with methanol, were determined by capillary electrophoresis (CE) using phosphate buffer pH 2.5 and U.V. detection at 210 nm. Histamine was well separated from the other co-extracted components under the given CE condition without any cleanup of the methanol extract. The average recovery of spiked histamine in various types of fish samples was 96%. Using the same methanol extracts from various fish samples, we then compared histamine concentration obtained by CE and fluorometric methods.     

Relationship between alignment layer polymer surface structures and liquid crystal display parameters

The polar alignment layer (AL) surface provided relatively small liquid crystal (LC) pretilt angles while polyimides with long alkyl side chains gave relatively large LC pretilt angles. The results suggest that LC pretilt angles, in addition to an anchoring effect, are greatly affected by both electronic and steric interactions between LC molecules and a polyimide alignment layer surface. Rubbing with a cotton cloth induces functional groups, side chains, and repeat units at the surface of a liquid crystal polyimide AL to re-orient. It was discovered that rubbing induced polar functional groups and repeat units to re-orient out-of-the-plane of the surface, and it made non-polar aliphatic side chains partially re-orient inwards, toward the bulk of the film.     

Uranium recovery via melt separation of rare earth elements and chemical oxidation

Journal of Radioanalytical and Nuclear Chemistry - Pyroprocessing of spent fuels, especially the recovery of U, improves the overall efficiency of nuclear recycling. The recovery of U/Transuranic...