Efficient synthesis of piperidine derivatives using dendrimer based catalytical pockets

The synthesis of highly functionalized piperidine derivatives using amine functionalized maltitol-cored dendritic polymer (MAL-G0) in acetonitrile as the reaction medium is reported. A variety of piperidine derivatives were synthesized and the reaction gave an excellent yield of 89%–95%. The highly functionalized nature of the catalyst provided large number of active sites which resulted in good yield within a short period of time. Maltitol is a carbohydrate polyol system which was chosen here as the core for the synthesis of the dendritic catalyst; it was an effective approach for the preparation of piperidine like medicinal compounds. Maltitol-cored dendritic polymer was effectively synthesized and characterized using GPC, TG, UV–Visible, IR, and NMR techniques and also all the synthesized piperidine derivatives were characterized using LCMS, IR, and NMR techniques.     

Synthetic studies on indolocarbazoles: total synthesis of staurosporine aglycon

A synthesis of staurosporine aglycon and its analogs was achieved in a 28-36% overall yield starting from 2-methylindole. The prominent key steps for the synthesis of the indolocarbazole alkaloids involved electrocyclization and nitrene insertion reactions.     

Perfect equilibrium and lexicographic beliefs

We extend the results of Blume, Brandenberger, and Dekel (1991b) to obtain a finite characterization of perfect equilibria in terms of lexicographic probability systems (LPSs). The LPSs we consider are defined over individual strategy sets and thus capture the property of independence among players' actions. Our definition of a product LPS over joint actions of the players is shown to be canonical, in the sense that any independent LPS on joint actions is essentially equivalent to a product LPS according to our definition. Received February 2002/Final version June 2002 We would like to thank Adam Brandenburger, Eddie Dekel, Arthur Robson, Peter Streufert, and Robert Wilson for their helpful comments. Govindan acknowledges research support from the Social Sciences and Humanities Research Council of Canada.     

The multi-cavity free-electron laser

Analysis is made of a free-electron laser with many optical cavities where the cavities communicate with each other, not optically, but through the electron beam. Analytic analysis is made in a one-dimensional, linear approximation. A general expression is given for the growth rate in the exponential (high current) regime. In the regime where lethargy is important expressions are given in the two opposite limits of small and large numbers of cavities and bunches. Numerical simulation results, still in the one-dimensional approximation, but including nonlinearities, are presented. Three examples of the multi-cavity free-electron laser (MC/FEL) are presented.     

Synthesis of 5-trifluoromethyl-5,8-dideazafolic acid and 5-trifluoromethyl-5,8-dideazaisofolic acid

The target folate analogue 5-trifluoromethyl-5,8-dideazafolic acid has been elaborated in a seven-step reaction sequence beginning with 2-fluoro-6-trifluoromethylbenzonitrile. The bridge-reversed isomer 5-trifluoromethyl-5,8-dideazaisofolic acid was prepared in six steps using the common intermediate 2,6-diamino-3,4-dihydro-4-oxo-5-trifluoromethylquinazoline. The key intermediate 2-amino-3,4-dihydro-4-oxo-5-trifluoromethyl-quinazoline was prepared using two distinct synthetic routes and the resulting products were found to be identical.     

Enhanced sensitivity of self-assembled-monolayer-based SPR immunosensor for detection of benzaldehyde using a single-step multi-sandwich immunoassay

This paper describes the fabrication and sensing characteristics of a self-assembled monolayer (SAM)-based surface plasmon resonance (SPR) immunosensor for detection of benzaldehyde (BZ). The functional sensing surface was fabricated by the immobilization of a benzaldehyde–ovalbumin conjugate (BZ–OVA) on Au-thiolate SAMs containing carboxyl end groups. Covalent binding of BZ–OVA on SAM was found to be dependent on the composition of the base SAM, and it is improved very much with the use of a mixed monolayer strategy. Based on SPR angle measurements, the functional sensor surface is established as a compact monolayer of BZ–OVA bound on the mixed SAM. The BZ–OVA-bound sensor surface undergoes immunoaffinity binding with anti-benzaldehyde antibody (BZ-Ab) selectively. An indirect inhibition immunoassay principle has been applied, in which analyte benzaldehyde solution was incubated with an optimal concentration of BZ-Ab for 5 min and injected over the sensor chip. Analyte benzaldehyde undergoes immunoreaction with BZ-Ab and makes it inactive for binding to BZ–OVA on the sensor chip. As a result, the SPR angle response decreases with an increase in the concentration of benzaldehyde. The fabricated immunosensor demonstrates a low detection limit (LDL) of 50 ppt (pg mL⁻¹) with a response time of 5 min. Antibodies bound to the sensor chip during an immunoassay could be detached by a brief exposure to acidic pepsin. With this surface regeneration, reusability of the same sensor chip for as many as 30 determination cycles has been established. Sensitivity has been enhanced further with the application of an additional single-step multi-sandwich immunoassay step, in which the BZ-Ab bound to the sensor chip was treated with a mixture of biotin-labeled secondary antibody, streptavidin and biotin–bovine serum albumin (Bio–BSA) conjugate. With this approach, the SPR sensor signal increased by ca. 12 times and the low detection limit improved to 5 ppt with a total response time of no more than ca. 10 min. Figure A single-step multi-sandwich immunoassay step increases SPR sensor signal by ca. 12 times affording a low detection limit for benzaldehyde of 5 ppt     

Ammonium uranyl carbonate (AUC) based process of simultaneous partitioning and reconversion for uranium and plutonium in fast breeder reactors (FBRs) fuel reprocessing

Ammonium uranyl carbonate (AUC) based process of simultaneous partitioning and reconversion for uranium and plutonium is developed for the recovery of uranium and plutonium present in spent fuel of fast breeder reactors (FBRs). Effect of pH on the solubility of carbonates of uranium and plutonium in ammonium carbonate medium is studied. Effect of mole ratios of uranium and plutonium as a function of uranium and plutonium concentration at pH 8.0–8.5 for effective separation of uranium and plutonium to each other is studied. Feasibility of reconversion of plutonium in carbonate medium is also studied. The studies indicate that uranium is selectively precipitated as AUC at pH 8.0–8.5 by adding ammonium carbonate solution leaving plutonium in the filtrate. Plutonium in the filtrate after acidified with concentrated nitric acid could also be precipitated as carbonate at pH 6.5–7.0 by adding ammonium carbonate solution. A flow sheet is proposed and evaluated for partitioning and reconversion of uranium and plutonium simultaneously in the FBR fuel reprocessing.     

Analytical methods for selected emerging contaminants in human matrices—a review

Emerging contaminants are a broad category of chemicals, previously unknown or unrecognized as being of concern, but which, because of their potential health effects associated with human exposure, are under increasing scrutiny. To accurately measure their levels in biological matrices, specific and sensitive analytical methods have recently been developed. We have reviewed here the methods used for analysis of selected emerging organic contaminants, for example metabolites of organophosphate triesters, metabolites of new phthalates or phthalate substitutes, perchlorate, organic UV filters, and polycyclic siloxanes, in human matrices. Although the use of new techniques and approaches has been emphasized, we also acknowledge methods previously used for other contaminants and adapted for the emerging contaminants listed above. In all cases, chromatography and mass spectrometry were the techniques of choice, because of their selectivity and sensitivity for measurements at ng?g^?1 levels. Critical issues and challenges have been discussed, together with recommendations for further improvement in particular cases (e.g. metabolites of phthalates or their substitutes). In particular, the use of labeled internal standards, the availability of certified reference materials, and the need for interlaboratory comparison exercises are key aspects of further development of this field of research.