Total synthesis of (±)-hibiscone B and (±)-acyl hibiscone B

The first total syntheses of the furanosesquiterpenoids hibiscone B and acyl hibiscone B are reported. The chemistry used to prepare hibiscone B solves an important challenge to the synthesis of other members of the furanosesquiterpenoid family of natural products, for which the parent molecule, hibiscone C, has shown promising biological activity.     

Effect of pressure and temperature on chromophore reorientation in a new syndioregic main‐chain hydrazone nonlinear optical polymer

Second harmonic generation (SHG) was used to measure the temperature dependence of the reorientation activation volume (ΔV*) of a syndioregic main‐chain hydrazone (SMCH) nonlinear optical polymer. The decay of the SHG signal from poled films of SMCH was recorded at hydrostatic pressures up to 2924 atm and at temperatures between 25 °C below the glass‐transition temperature (T_g) to 20 °C above it. ΔV* for pressures less than 500–1000 atm and T > T_g decreased as the temperature was increased. For pressures greater than 1000 atm, ΔV* was essentially constant for all temperatures. In addition, the size of ΔV* indicated that the chromophore in this main chain was internally flexible. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 895–900, 2001     

Liquid chromatography at critical conditions in ternary mobile phases: Gradient elution along the critical line

In ternary mobile phases consisting of acetone, methanol, and water, the retention of PEG on reversed‐phase columns is independent on molar mass at certain compositions of the mobile phase. Along this critical adsorption line, the retention of polypropylene glycol varies quite strongly, which can be utilized in the separation of block copolymers. Gradient elution along the critical line allows a baseline separation of all oligomers in polypropylene glycol up to approximately 25 propylene oxide units. The same resolution can be achieved in the separation of ethylene oxide‐propylene oxide block copolymers, regardless of the length of the ethylene oxide block.     

Direct patterning of microelectrode arrays using femtosecond laser micromachining

Micron-resolution microelectrodes and microelectrode arrays are commonly used in Lab-on-a-chip applications, typically for particle and fluidic sensing or pumping applications. The common method of fabricating such structures is to use conventional photolithography, which involves several steps, any of which can affect the quality and dimension of the final structure. Here we present an alternative method of creating microelectrodes using direct laser patterning. This is a significantly simpler and faster fabrication route requiring a single patterning step, and which also allows design changes to be implemented quickly, without having to re-manufacture a photolithographic mask. To confirm the suitability of this approach to fabricating microelectrodes, a complex multielectrode array design for neuron stimulation was directly laser-patterned.     

Origins of selectivity in pericyclic reaction cascades for the synthesis of gambogin and lateriflorone

[reaction: see text] Quantum mechanical calculations demonstrate that the second step of a Claisen-Diels-Alder reaction cascade controls regioselectivity that gives advanced intermediates for the synthesis of gambogin and 1-O-methyllateriflorone.     

High-throughput synthesis and screening of ternary metal alloys for electrocatalysis

We report the application of a new method for the high-throughput synthesis and screening of thin film materials and its application to the discovery of electrocatalysts. Results are presented for the PtPdAu ternary alloy system with respect to activity for oxygen reduction. The results reveal an enhancement in activity for a range of PtPd alloy compositions over either of the pure elements. An optimum composition range of ternary alloys with significant activity was also identified. A correlation was also investigated between the surface reduction potential and the activity for oxygen reduction in both binary and ternary alloys. The results demonstrate the potential of the methodology for the discovery and optimization of electrocatalysts for a wide range of applications.