Novel 3-deoxy analogs of the anti-HBV agent entecavir: synthesis of enantiomers from a single chiral epoxide

A synthesis of novel 3^′-deoxy analogs of the anti-HBV agent entecavir (BMS-200475) was devised using regioselective ring opening of suitable cyclopentene epoxides as the key step. This versatile approach afforded access to an enantiomeric pair of carbocyclic nucleosides from a single chiral intermediate.     

1,3,5-Tri- and 1,3,4,5-tetra-substituted 1,4-diazepin-2-one solid-phase synthesis

Solid-phase syntheses of 1,3,5-tri-substituted and 1,3,4,5-tetra-substituted 1,4-diazepin-2-ones 15-18 have been accomplished by employing inexpensive commercially available alpha- and beta-amino acids on Wang resin. Reductive amination of the imine formed by condensation of Wang aldehyde resin respectively with beta-alaninate 2 and beta-homophenylalaninate 3, followed by aminoacylation with a set of alpha-N-Boc amino acids (Phe epsilon-( Z)-Lys, and Leu) gave tertiary amide resins 7 and 8. Exposure of resins 7 and 8 to an excess of vinyl magnesium bromide in the presence of copper cyanide gave the corresponding gamma,delta-unsaturated ketone resins 9 and 10 by way of a cascade addition. Diazepinones were made by Boc deprotection and intramolecular reductive amination. To diversify the heterocycle, N-alkylation was performed using a series of alkyl halides. Alternatively, diazepinones 15e-g were obtained from treatment of methyl beta-alaninate resins 4 and 20 under similar copper-catalyzed cascade conditions to afford the gamma,delta-unsaturated ketone 21, which was acylated using alpha-N-Fmoc-amino acids (Phe, Trp, gamma-(t-Bu)-Glu). Formation of diazepinones 15 followed a similar protocol, after Fmoc removal with piperidine. Cleavage of the heterocycles with TFA/TES 95:5 gave the N1-p-hydroxybenzyl diazepinones 15-18 in overall isolated yields from 6 to 24% after purification in purities ranging from 81 to 100% according to LCMS analysis.     

Novel 3',6'-anhydro and N12,N13-bridged glycosylated fluoroindolo[2,3-a]carbazoles as topoisomerase I inhibitors. Fluorine as a leaving group from sp3 carbon

[reaction: see text] Both 6'- and 4'-fluoro-glycosylated indolo[2,3-a]carbazoles are substrates for base-induced loss of fluorine as a leaving group from sp3 carbon. In the case of alpha-N-glycosylated substrate 3, loss of fluorine from the 6'-position leads to 3,6-anhydroglucose analogue 1. A novel N12,N13-bridged sugar analogue 2 results from loss of 4'-fluorine from beta-N-glycosylated analogue 4. Both analogues 1 and 2 display topo I inhibitory potencies similar to camptothecin.     

Reconfigurable wavefront sensor for ultrashort pulses

A highly flexible Shack-Hartmann wavefront sensor for ultrashort pulse diagnostics is presented. The temporal system performance is studied in detail. Reflective operation is enabled by programming tilt-tolerant microaxicons into a liquid-crystal-on-silicon spatial light modulator. Nearly undistorted pulse transfer is obtained by generating nondiffracting needle beams as subbeams. Reproducible wavefront analysis and spatially resolved second-order autocorrelation are demonstrated at incident angles up to 50° and pulse durations down to 6 fs.     

Microscale analysis of proteins in inner ear tissues and fluids with emphasis on endolymphatic sac, otoconia, and organ of Corti

Here we describe preparatory techniques adapted for the study of proteins of inner ear tissues and fluids that have allowed us to apply state-of-the-art analytical techniques in spite of the minute size and anatomical complexities of this organ. Illustrative examples address unresolved issues of functional and clinical significance. First, we demonstrate how quick-freezing and freeze drying prevents artifacts that arise from sampling endolymphatic sac (ES) content in the liquid state. This set the stage for the generation of the first protein profile of the ES. Identification of crucial proteins will help elucidate mechanisms of endolymph volume regulation and pathogenesis of Meniere's disease. Second, we show how a unique situation allowed identification of otoconial proteins by mass spectrometric analysis without prior separation and we discuss possible roles for these minor otoconins in otoconial development and prevention of degenerative diseases that affect balance. Finally, we demonstrate techniques for the precise dissection of organ of Corti and its substructures, while preserving their near normal chemical state. We extended an earlier study in which we identified a novel calcium-binding protein by IEF, oncomodulin, localized in the outer hair cells and show here the applicability of prefractionation for the screening of calcium-binding proteins of organ of Corti. These studies demonstrate how advanced preparatory and analytical techniques can be applied to studies of the inner ear.     

Functionality and Observed Versus Predicted Gel Points

An ambiguity in use of the term functionality is pointed out. The two most widely used relations (Flory, and Stockmayer and Kahn) connecting extent of reaction at the gel point and functionality are examined. The relations are shown mathematically to lead to the same result when all assumptions and definitions are considered. Measured gel points of polyesters are compared with those predicted by the equation. Deviations were less than 10% of the predicted values.

An ambiguity in definition has been observed for the word functionality which has led to unnecessary confusion of thought. It is believed that this confusion has often occurred and has been seen in the literature quite recently [1,2]. On the one hand, functionality has been used to mean the number of chain ends united at the branch points in a polymer network. Since branch points can unite no fewer than three chain ends, functionality in this sense can take on values of three or greater. Networks are most often three or four functional. If more than one type of branch point is present, the average functionality can be calculated as a fraction with a value above three.