Preparation of enol ethers by carbonyl olefination utilizing an alkoxymethyl chloride-titanocene(II) system

Aldehydes, ketones, esters and lactones are transformed into enol ethers or 1,2-dialkoxy-1-alkenes by treatment with organotitanium species prepared from alkoxymethyl chlorides and a titanocene(II) complex.     

Proteomic LC-MS systems using nanoscale liquid chromatography with tandem mass spectrometry

Current nano-scale liquid chromatography-tandem mass spectrometry (nanoLC-MS/MS) approaches in proteome research are reviewed from an analytical perspective. For comprehensive analysis of cellular proteins, analytical methods with higher resolution, sensitivity, and wider dynamic range are required. Miniaturized LC coupled with tandem mass spectrometry is currently one of the most versatile techniques. In this review, the current status of nanoLC-MS/MS systems as well as data management systems is addressed. In addition, the future prospects for complete proteomics are discussed.     

Synthesis of Optically Active Vasicinone Based on Intramolecular Aza-Wittig Reaction and Asymmetric Oxidation(1)

Both optical isomers of a quinazoline alkaloid, vasicinone, were synthesized by two different methods. The first method used (3S)-3-hydroxy-gamma-lactam as a chiral synthon, which was, after O-TBDMS protection, o-azidobenzoylated followed by treatment with tri-n-butylphosphine to afford (S)-(-)-vasicinone via the tandem Staudinger/intramolecualr aza-Wittig reaction. The second method utilized asymmetric oxygenation of deoxyvasicinone with (1S)-(+)- or (1R)-(-)-(10-camphorsulfonyl)oxaziridine (the Davis reagent), respectively. The aza-enolate anion of deoxyvasicinone was treated with (S)-(+)-reagent to afford (R)-(+)-vasicinone in 71% ee, while the reaction with (R)-(-)-reagent gave (S)-(-)-vasicinone in 62% ee. The optical purity was analyzed by HPLC on specially modified cellulose as a stationary phase. These results provided a facile method to prepare both optical isomers of vasicinone and confirmed the recently reversed stereochemistry of natural (-)-vasicinone.     

Molecular orientation of azobenzene chromophores in ultrathin polymer nanosheets studied by attenuated total reflection spectroscopy

This paper describes characterization of molecular orientation for azobenzene moieties in a polymer nanosheet. Copolymers of N-[4-(phenylazo)phenyl] acrylamide (PAZoA) with tert-pentyl acrylamide (tPA) were synthesized and the monolayers deposited on tapered quartz waveguides by Langmuir–Blodgett (LB) technique. Spectroscopic properties of the copolymer (p(tPA/PAZoA)) monolayers were monitored by integrated optical waveguide technique on the molecular level. Molecular orientation of the azobenzene was precisely determined by polarized absorption spectra. It was found that the azobenzene groups took a horizontal orientation and distributed uniformly in the p(tPA/PAZoA) monolayer without significant PAZoA aggregation. Photoisomerization process from trans to cis form was also investigated. More than half of the trans form (60–70%) was photoisomerized under unpolarized light irradiation, and the photoisomerization rate was independent on the PAZoA contents. This implies that the microenvironment of PAZoA moieties was almost the same in three different p(tPA/PAZoA) monolayers.     

One-dimensional ion transport in self-organized columnar ionic liquids

New fan-shaped ionic liquids forming columnar liquid crystalline phases have been prepared to obtain one-dimensional ion-transporting materials. The ionic liquids consist of two incompatible parts: an imidazolium-based ionic part as an ion-conducting part and tris(alkyloxy)phenyl parts as insulating parts. Two compounds having octyl and dodecyl chains have been synthesized. Self-assembly of these materials leads to the formation of thermotropic hexagonal columnar liquid crystalline states at room temperature. Anisotropic one-dimensional ionic conductivities have been successfully measured by the cells having comb-shaped gold electrodes. The self-organized columns have been aligned macroscopically in two directions by shearing perpendicular and parallel to the electrodes. The ionic conductivities parallel to the column axis are higher than those perpendicular to the axis. The incorporation of lithium salts in these columnar materials leads to the enhancement of the ionic conductivities and their anisotropy. These materials would be useful for anisotropic transportation of ions at the nanometer level.     

Concise synthesis of anti-HIV-1 active (+)-inophyllum B and (+)-calanolide A by application of (-)-quinine-catalyzed intramolecular oxo-Michael addition

(-)-Quinine-catalyzed intramolecular oxo-Michael addition (IMA) of 7-hydroxy-5-methoxy-8-tigloylcoumarins was developed for the enantioselective construction of 2,3-dimethyl-4-chromanone systems in the context of the asymmetric synthesis of anti-HIV-1 active Calophyllum coumarins. Combination of the IMA and MgI(2)-assisted demethylation of the 5-methoxy group along with isomerization of the formed chromanone systems as key steps successfully led to the concise synthesis of (+)-inophyllum B and (+)-calanolide A, possible candidates for AIDS drugs. Further examination of the asymmetric IMA with cinchona alkaloids lacking a methoxy group on the quinoline skeleton suggested the influence of the methoxy substituent on stereoselectivity at the stereogenic centers of the chromanone systems.     

Linear NiII-MnIII2-NiII tetramers: an oligomeric component of the MnIII2NiII single-chain magnets

Heterometallic linear tetramers [Mn(5-R-saltmen)Ni(pao)(bpy)(2)](2)(ClO(4))(4) (5-R-saltmen(2-) = N,N'-1,1,2,2-tetramethylethylene bis(5-R-salicylideneiminate); pao(-) = pyridine-2-aldoximate; bpy = 2,2'-bipyridine, R = H, 1; Cl, 2; Br, 3; MeO, 4) have been synthesized and structurally characterized. These compounds exhibit a [Ni(II)-NO-Mn(III)-(O)(2)-Mn(III)-ON-Ni(II)] skeleton where -ON- is an oximate bridge between Mn(III) and Ni(II) ions and -(O)(2)- is a bi-phenolate bridge between Mn(III) ions. These tetramers can be seen as oligomeric units of the heterometallic Mn(III)(2)-Ni(II) chain observed in a family of single-chain magnets (Clérac, R.; Miyasaka, H.; Yamashita, M.; Coulon, C. J. Am. Chem. Soc. 2002, 124, 12837. Miyasaka, H.; Clérac, R.; Mizushima, K.; Sugiura, K.; Yamashita, M.; Wernsdorfer, W.; Coulon, C. Inorg. Chem. 2003, 42, 8203.). Magnetic measurements on these tetramers confirm the nature of the magnetic interactions reported for the Mn(III)(2)-Ni(II) chains: a strong antiferromagnetic Mn(III)/Ni(II) coupling via the oximate bridge (J(Ni-Mn) ranges from -23.7 to -26.1 K) and a weak ferromagnetic Mn(III)/Mn(III) coupling through the bi-phenolate bridge (J(Mn-Mn) ranges from +0.4 to +0.9 K). These magnetic interactions lead to tetramers with an S = 2 ground state.     

Lannotinidines A-G, new alkaloids from two species of Lycopodium

Seven new Lycopodium alkaloids, lannotinidines A-G (1-7), have been isolated from the club moss Lycopodium annotinum and L. annotinum var. acrifolium. Stereochemistry of 1-7 was elucidated by combination of NOESY correlations and chemical transformation. Lannotinidines B-E (2-5) elevated NGF mRNA expression.     

MnIII2 (5-Rsaltmen)2NiII(pao)2(L)]2+: an S(T)=3 building block for a single-chain magnet that behaves as a single-molecule magnet

Mn(III)-Ni(II)-Mn(III) linear-type trinuclear complexes bridged by oximate groups were selectively synthesized by the assembly reaction of [Mn2(5-Rsaltmen)2(H2O)2](ClO4)2 (5-Rsaltmen2-=N,N'-(1,1,2,2-tetramethylethylene) bis(5-R-salicylideneiminate); R=Cl, Br) with [Ni(pao)2(phen)] (pao-=pyridine-2-aldoximate; phen=1,10-phenanthroline) in methanol/water: [Mn2(5-Rsaltmen)2Ni(pao)2(phen)](ClO4)2 (R=Cl, 1; R=Br, 2). Structural analysis revealed that the [Mn(III)-ON-Ni(II)-NO-Mn(III)] skeleton of these trimers is in every respect similar to the repeating unit found in the previously reported series of 1D materials [Mn2(saltmen)2Ni(pao)2(L1)2](A)(2) (L(1)=pyridine, 4-picoline, 4-tert-butylpyridine, N-methylimidazole; A=ClO4-, BF4-, PF6-, ReO4-). Recently, these 1D compounds have attracted a great deal of attention for their magnetic properties, since they exhibit slow relaxation of the magnetization (also called single-chain magnet (SCM) behavior). This unique magnetic behavior was explained in the framework of Glauber's theory, generalized for chains of ferromagnetically coupled anisotropic spins. Thus, in these 1D compounds, the [Mn(III)-ON-Ni(II)-NO-Mn(III)] unit was considered as an S(T)=3 anisotropic spin. Direct-current magnetic measurements on 1 and 2 confirm their S(T)=3 ground state and strong uniaxial anisotropy (D/k(B) approximately -2.4 K), in excellent agreement with the magnetic characteristic deduced in the study on the SCM series. The ac magnetic susceptibility of these trimers is strongly frequency-dependent and characteristic of single-molecule magnet (SMM) behavior. The relaxation time tau shows a thermally activated (Arrhenius) behavior with tau0 approximately 1x10(-7) s and Delta(eff)/k(B) approximately 18 K. The effective energy barrier for reversal of the magnetization Delta(eff) is consistent with the theoretical value (21 K) estimated from |D| S2T. The present results reinforce consistently the interpretation of the SCM behavior observed in the [Mn2(saltmen)2Ni(pao)2(L1)2](A)2 series and opens new perspectives to design single-chain magnets.