Stereoselective synthesis of the macrolactone core of (+)-neopeltolide

A stereoselective synthesis of the macrolactone core of the potent anticancer agent neopeltolide is disclosed. The key steps of the synthesis include asymmetric allylation using Krische' protocol, conjugate reduction using MacMillan's methodology, and an asymmetric hetero-Diels-Alder reaction using Jacobsen's catalyst. Substrate controlled diastereoselective 1,3-anti reduction of a keto alcohol, Luche reduction followed by Ireland-Claisen rearrangement, oxymercuration, and reductive lithiation are other key steps.     

Negative muon capture in3He

We compute the partial capture rate of negative muons in³He by following the analysis of Peterson to include the relativistic corrections and the exchange effects, for various values of theg _p /g _A ratio. We also calculate the total capture rate. The ground state of³He is assumed to be spherical. The radial dependence of the ground state wave function is taken to be (a) one parameter Irving function, (b) a modified three-parameter Irving function and (c) a function having ‘soft-core’, whose parameters have been fixed in a variational calculation of the binding energy of the triton using a non-local momentum-dependent potential involvingp ² terms. The calculated values of the capture rates are compared with the experimental data to find a value for theg _p /g _A ratio.     

Strategy for purifying maltose binding protein fusion proteins by affinity precipitation

The maltose binding protein (MBP) affinity tag has been extensively used for protein purification. A commercial grade cationic starch could precipitate MBP or an MBP-tagged protein quantitatively by simultaneous addition of 10% (w/v) polyethylene glycol (PEG) and 50 mM calcium chloride. The precipitated MBP or MBP-tagged protein could be selectively dissociated by suspending the precipitate in 1 M NaCl. In the case of a soluble MBP fusion with a fragment of human immunodeficiency virus protein gp120, 38% of the contaminating proteins could be removed by precipitation with PEG/CaCl(2) and 100% of the fusion protein was recovered. In all cases, the purified proteins showed a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the expected changes in fluorescence emission spectra upon binding to maltose.     

Collaboration in tool development and capacity investments in high technology manufacturing networks

The procurement of capital intensive tools for hi-tech industries is one of the most complex tasks. Astronomical amounts of capital are invested in the processing equipment. Further, there is a large effort from the original equipment manufacturer (OEM) in customizing the high capital intensive equipment to suit their production process. This problem has received little attention from the quantitative decision making literature. For the first time we analyze the problem of OEM deciding on collaborating with the tool supplier via a special type of contract which we refer as “collaboration options”. We show that there are benefits to both the OEM and the tool suppliers from the collaboration.     

The sulfinyl moiety as an internal nucleophile. 2. Stereoselective synthesis of (-)-galantinic acid via 1,3-asymmetric induction

A stereoselective synthesis of (-)-galantinic acid is disclosed. The key steps include hydrolytic kinetic resolution of a racemic epoxide and regio- and stereoselective heterofunctionalization of an olefin, using a pendant sulfinyl group as the nucleophile. The participation of the sulfinyl group was unambiguously proven by conducting the reaction in the presence of H(2)(18)O.     

A new coordination mode of the photometric reagent glyoxalbis(2-hydroxyanil) (H2gbha): bis-bidentate bridging by gbha2- in the redox series [(mu-gbha)[Ru(acac)2]2]n (n = -2, -1, 0, +1, +2), including a radical-bridged diruthenium(III) and a Ru(III)/Ru(IV) intermediate

The bis-bidentate bridging function of gbha2- with N,O-/N,O- coordination was observed for the first time in the complex (mu-gbha)[Ru(III)(acac)2]2 (1). Density functional theory calculations of 1 yield a triplet ground state with a large (deltaE > 6000 cm(-1)) singlet-triplet gap. Intermolecular antiferromagnetic coupling was observed (J approximately -5.3 cm(-1)) for the solid. Complex 1 undergoes two one-electron reduction and two one-electron oxidation steps; the five redox forms [(mu-gbha)[Ru(acac)2]2]n (n = -2, -1, 0, +1, +2) were characterized by UV-vis-NIR spectroelectrochemistry (NIR = near infrared). The paramagnetic intermediates were also investigated by electron paramagnetic resonance (EPR) spectroscopy. The monoanion with a comproportionation constant K(c) of 2.7 x 10(8) does not exhibit an NIR band for a Ru(III)/Ru(II) mixed-valent situation; it is best described as a 1,4-diazabutadiene radical anion containing ligand gbha*3-, which binds two ruthenium(III) centers. A Ru(III)-type EPR spectrum with g1 = 2.27, g2 = 2.21, and g3 = 1.73 is observed as a result of antiferromagnetic coupling between one Ru(III) and the ligand radical. The EPR-active monocation (K(c) = 1.7 x 10(6)) exhibits a broad (deltanu(1/2) = 2600 cm(-1)) intervalence charge-transfer band at 1800 nm, indicating a valence-averaged (Ru3.5)2 formulation (class III) with a tendency toward class II (borderline situation).     

Crystal structure of triphenylphosphine-(1-(di(trifluoromethyl)-hydroxymethyl)-cyclopentadienyl)-(1,2-di(carboxymethyl) ethylene-1-yl) ruthenium (0)

The structure of triphenylphosphine — (1 — (di(trifluoromethyl) — hydroxymethyl) — cyclopentadienyl) — (1,2 — di(carboxymethyl)ethylene — 1 — yl) — ruthenium (0) has been studied by single-crystal X-ray diffraction techniques. This compound, [C₅ H₄(CF₃)2 COH] Ru(PPh₃)C2(CO₂Me)₂H, crystallizes in the triclinic space groupP¯1 witha =10.131,b= 15.107,c= 10.798 Å, = 102.14, = 107.04, = 89.64° andZ = 2. The structure was refined by block-diagonal least-squares methods to a finalR value of 0.042, including hydrogen atoms. The compound contains a dicarboxymethylethylene ligand coordinated to ruthenium both through a ketonic oxygen and through a metal--carbon -bond. An intramolecular hydrogen bond is observed. Details of the structure are reported, and the structures of several Ru(0) complexes are compared.     

Iron doped lithium cobalt oxides as lithium intercalating cathode materials

Layered transition metal oxides of the formula LiMO₂ have good lithium insertion properties for which reason LiCoO₂ and LiNiO₂ have been exploited in practical lithium rocking chair batteries. Another member of the LiMO₂ series, LiFeO₂, should be an attractive cathode material considering the cheapness and environment-friendliness of iron compounds. Its rock-salt structure, however, does not allow significant amounts of lithium to be reversibly intercalated in its structure. Synthesis of layered LiFeO₂ and study of its lithium intercalating properties have been of limited success. Therefore, an attempt has been made here to study LiCo_1−yFe_yO₂ solid solutions (0 ≤ y ≤ 0.4) as prospective cathode materials. XRD, FTIR, Atomic absorption spectroscopy, Particle size and Surface area analysis were carried out in this regard towards the physical characterization of the entire series of LiCo_1−yFe_yO₂ compounds. The electrochemical discharge capacity of these materials is explained as a function of the iron content.