Enantioselective epoxidation by the chiral auxiliary approach: Asymmetric total synthesis of (+)-Ambrisentan

Enantioselective and a highly concise total synthesis of Ambrisentan are described. The chiral auxiliary controlled enantioselective epoxidation (Azerad protocol), photochemical regioselective epoxide opening, and base mediated ester hydrolysis reactions are the key reactions.     

Traveling-wave atom cavity interaction in the single-atom microlaser

We demonstrated traveling-wave atom-cavity interaction in the single-atom microlaser by tilting the atomic beam from its usual orientation of normal incidence with respect to the cavity mode. Laser-tuning curves, measured for various excitation pulse areas, are in good agreement with one-atom microlaser-maser theory.     

Modeling of a continuous pretreatment reactor using computational fluid dynamics

Computational fluid dynamic simulations are employed to predict flow characteristics in a continuous auger driven reactor designed for the dilure acid pretreatment of biomass. Slurry containing a high concentration of biomass solids exhibits a high viscosity, which poses unique mixing issues within the reactor. The viscosity increases significantly with a small increase in solids concentration and also varies with temperature. A well-mixed slurry is desirable to evenly distribute acid on biomass, prevent buildup on the walls of the reactor, and provides an uniform final product. Simulations provide flow patterns obtained over a wide range of viscosities and pressure distributions, which may affect reaction rates. Results provide a tool for analyzing sources of inconsistencies in product quality and insight into future design and operating parameters.     

Total Synthesis of a Mevinic Acid Analog

Total synthesis of mevinic acid analog 1 has been achieved efficiently starting from chiral 2,3‐O‐isopropylidene‐D ‐glyceraldehyde ( 2 ). The synthesis involves Mitsunobu reaction and Evans' intramolecular oxa‐Michael syn‐addition reactions as key steps.     

Fourier phase microscopy for investigation of biological structures and dynamics

By use of the Fourier decomposition of a low-coherence optical image field into two spatial components that can be controllably shifted in phase with respect to each other, a new high-transverse-resolution quantitative-phase microscope has been developed. The technique transforms a typical optical microscope into a quantitative-phase microscope, with high accuracy and a path-length sensitivity of lambda/5500, which is stable over several hours. The results obtained on epithelial and red blood cells demonstrate the potential of this instrument for quantitative investigation of the structure and dynamics associated with biological systems without sample preparation.     

Crystal structure and conformation of Tilorone monohydrate [2,7-{bis1-oxo-4-(1-piperidinyl)butyl}-9H-fluoren-9-one] monohydrate: an antiviral agent and an interferon inducer

Tilorone is an orally active pharmacological agent that protects mice against infections with RNA and DNA viruses. It is also the only known small molecule that is an interferon inducer. It has anti-tumor and anti-inflammatory properties and was shown to interact and influence the immune mechanisms in human and animals. Structure-function studies of Tilorone and its several analogs have been undertaken in our laboratories with an objective to correlate the structural features with the immuno-suppressive activity. Crystals of the title compound are triclinic, space group , with the following crystallographic parameters: a = 7.068(2), b = 9.030(3), c = 23.635(3) Å, = 103.91(2), = 108.49(2), = 93.84(4)°, V = 1371.9 ų, _obs = 1.17 Mg/m³, _calc = 1.168 Mg/m³ and Z = 2. The structure was solved with CAD-4 data, using SHELX-86 program and refined to a final R value of 0.063. The oxobutyl groups are in an extended zig-zag conformation and are co-planar with the central fluorenone chromophore. The two terminal piperidine rings are in the preferred chair conformation. The crystal structure lends support to the intercalative mechanism of action for Tilorone. We hypothesize that the stereochemistry and molecular geometry of these drugs and/or their active metabolites affect both the receptor interaction and the mode of immunomodulation. Comparison of the biological effects of the various tilorone analogs should allow us to obtain some more insight into their structure-function correlations.     

Photon recyclers

We present a radical approach for improving the efficiency of optically pumped NMMW lasers in which the Manley-Rowe limit is transcended by recycling pump photons. The resulting new class of lasers, called photon recyclers, can be described as heat engines in which heat is converted into coherent NMMW radiation using pump photons as a catalyst. Practical implementation of the proposed schemes by combining features of optically pumped NMMW lasers and gas dynamic expansion is discussed. Such systems may yield high power c.w. NMMW output.Work supported by U.S. Army Research Office, Durham, NC.