Enantioselective and diastereoselective syntheses of cyanohydrin carbonates

A new and general synthesis of alkyl cyanoformates is presented starting from the appropriate alcohol and oxalyl chloride. This is used to prepare enantiomerically pure cyanoformates from enantiomerically pure primary and secondary alcohols. Optimal conditions for the addition of various achiral cyanoformates to aldehydes catalysed by an enantiomerically pure titanium(salen) catalyst in the presence of potassium cyanide as a cocatalyst are developed. Under these conditions, two chiral cyanoformates also reacted with aldehydes to give cyanohydrin carbonates. The stereochemistry of this process is predominantly determined by the stereochemistry of the titanium(salen) catalyst and the stereochemistry of two of the cyanohydrin carbonates was confirmed by X-ray crystallography. In a further extension of the chemistry, a homogeneous system in which the potassium cyanide/18-crown-6 complex is used as the cyanide cocatalyst has been developed and the kinetics of this reaction show that it displays first order kinetics, provided at least 2 mol % of the potassium cyanide complex are employed.     

Charged pion production in 70 GeV/cK + p interactions

Inclusive charged pion production is studied in an exposure of BEBC, filled with hydrogen, to an incidentK ⁺ beam of 70 GeV/c. Total cross sections for pion production and inclusive longitudinal and transverse momentum distributions of π^?'s and of positive particles are presented and compared with data at lower energies. Earlier evidence for scaling in the fragmentation regions is confirmed. The central region π^? cross section increases proportionally top _LAB ^?1/4 ; positive particles show almost no energy dependence atx=0. Particle ratios π⁺/π^? are studied as a function ofx andy ^* and a comparison with 70 GeV/cK ^? p data is made. Analysis of structure functions for (ππ) pairs and of particle production associated with π^± triggers at large |x| in the context of quark/parton models, provides qualitative evidence for the diquark-quark structure of the proton.     

An estimation of the fine structure constant using fiber bundles

We calculateg ₀/e whereg ₀ is the strength of an elementary magnetic monopole ande the charge on the electron, in terms of a ratio of loop sizes in the twisted and untwisted principal fiber bundles withU(1) the structure group andR ³-{0} the base space. The result involves the present distance around theU(1) space and, rather surprisingly, the structure of the quantum gravitational vacuum. Combining our result with the expression foreg ₀ from the Dirac quantization condition gives a final estimate for the fine structure constant,1/100.     

Quadratic-Like Dynamics of Cubic Polynomials

A small perturbation of a quadratic polynomial f with a non-repelling fixed point gives a polynomial g with an attracting fixed point and a Jordan curve Julia set, on which g acts like angle doubling. However, there are cubic polynomials with a non-repelling fixed point, for which no perturbation results into a polynomial with Jordan curve Julia set. Motivated by the study of the closure of the Cubic Principal Hyperbolic Domain, we describe such polynomials in terms of their quadratic-like restrictions.     

PASADENA hyperpolarization of succinic acid for MRI and NMR spectroscopy

We use the PASADENA (parahydrogen and synthesis allow dramatically enhanced nuclear alignment) method to achieve 13C polarization of approximately 20% in seconds in 1-13C-succinic-d2 acid. The high-field 13C multiplets are observed as a function of pH, and the line broadening of C1 is pronounced in the region of the pK values. The 2JCH, 3JCH, and 3JHH couplings needed for spin order transfer vary with pH and are best resolved at low pH leading to our use of pH approximately 3 for both the molecular addition of parahydrogen to 1-13C-fumaric acid-d2 and the subsequent transfer of spin order from the nascent protons to C1 of the succinic acid product. The methods described here may generalize to hyperpolarization of other carboxylic acids. The C1 spin-lattice relaxation time at neutral pH and 4.7 T is measured as 27 s in H2O and 56 s in D2O. Together with known rates of succinate uptake in kidneys, this allows an estimate of the prospects for the molecular spectroscopy of metabolism.     

Electrochemical characterization of 17β-estradiol with fast-scan cyclic voltammetry

We have developed a sensitive and stable electrochemical method for 17β-estradiol (E2) detection using fast-scan cyclic voltammetry (FSCV). Recently, E2 was proposed to function as a rapid synaptocrine signaling molecule in the brain; however, methods to directly monitor subsecond fluctuations in E2 are currently unavailable, limiting our understanding of the dynamics and mechanism of rapid E2 release. FSCV at carbon-fiber microelectrodes enables subsecond detection of electroactive neurochemicals directly in tissues like the brain. Here, we have electrochemically characterized E2 using FSCV for use in a tissue matrix. The limit of detection of E2 is 31.2±2.5 nM with FSCV, which will enable low nanomolar fluctuations in extracellular E2 to be monitored with hundred millisecond temporal resolution. We also identify specific parameters for waveform modification to improve future detection. This method will significantly improve E2 sensing capabilities and will have far-reaching impacts on improving our understanding of dynamic E2 signaling in the brain.     

Highly active mesostructured silica hosted silver catalysts for CO oxidation using the one-pot synthesis approach

A facile one-pot approach gave isolated silver nanoparticles anchored on a mesostructured silica matrix in a self-assembled way; these gave 100% CO conversion in CO oxidation at room temperature, which is higher than or comparable to the conversion obtained using noble metal catalysts.