No description available.

No description available.

The starting material 3-sulfonyl-5-methoxy glutarimide was easily prepared via stepwise [3+3] annulation of N-benzyl R-sulfonylacetamide with unsaturated ester as we previously described. We wish we could build tetrahtdronaphthridine skeleton via stretching C-chain, modifying funtional group and RCM, then complete the synthesis of key intermediate of small molecule similar to RGD.

Abstract Chemistry for first year students has been identified by Tshwane University of Technology as one of the subjects with a low pass rate. It is apparent that students often memorize formulae and definitions, without understanding the underlying concepts required to work with abstract units of measure. We have found that the majority of students at this university are unable to balance reaction equations satisfactorily. They are also unable to predict the reaction yield, or identify limiting reagents. It is imperative that these and other related problems are overcome before any meaningful change to the high failure rate at first year level will be realized. All conventional forms of lecture presentation failed to make any significant impact on the success rate. Structured worksheets were developed and used, together with tactile models, to address the problems and the initial findings showed a marked improvement. It was discovered that the students’ problems originated from their inability to understand the meaning of subscripts and coefficients in chemical equations. The worksheets and the impact they have made on the students’ understanding of stoichiometry are shared in this paper.

A method for unsymmetric disulfide synthesis from carboxylic acids under photoredox conditions has been developed. N-Perthiophthalimide derivatives (Harpp reagents) are used as disulfurating reagents in a decarboxylative disulfuration. Though significant sulfide formation was observed when using less sterically-hindered (primary and secondary) Harpp reagents, tertiary Harpp reagents affording corresponding disulfides in good yields. At first glance, the reaction was expected to go through radical substitution directly on the Harpp reagent to obtain the observed disulfide and a phthalimidyl radical that would reoxidize the reduced photocatalyst. However, computational studies suggest a high barrier and endergonic reaction for such a mechanism due to the high energy of the liberated phthalimidyl radical (N-H BDE in phthalimide is predicted to be ~120 kcal/mol). Supported by calculation and experiments, an alternative mechanism was proposed: perthyl radicals generated from single electron reduction of Harpp reagent dimerized to form tetrasulfides, which are known to undergo efficient radical substitution to afford disulfides. Mechanistic studies on previously reported sulfurations using N-thiophthalimide derivatives suggested a similar mechanism - specifically that disulfides generated in situ undergo radical substitution to provide the sulfide products. Direct C-H disulfuration using Harpp reagents under a variety of conditions was also investigated, but found to have very limited substrate scope. It would appear that the instability of the disulfurating reagents, be they Harpp reagents or tetrasulfides generated therefrom, under the various oxidative conditions prevented the development of a general approach.

No description available.

Salvia divinorum is a hallucinogenic herb from the mint family, Lamiaceae. An estimated 1.8 million people over the age of 12 have used S. divinorum in their lifetime as of 2008. The abuse of S. divinorum is attractive to teens and young adults who wish to experiment with psychoactive materials. The plant material and extracts are widely available via the Internet, and it is known that S. divinorum will not show up on common drug screens. The active component in S. divinorum is salvinorin A, which is a non-nitrogenous diterpene that is a highly selective kappa opioid receptor (KOR) agonist, reported to be the most potent naturally occurring hallucinogen. Since salvinorin A is such a selective and potent agonist of the KOR, there is interest in researching analogues in efforts to develop and understand therapeutic drugs for depression, schizophrenia, and other mental illnesses, resulting in the discovery of analogues with increased potency. These semi-synthetic salvinorin analogues have been abused by spraying the drug on innocuous plant material or on cigarette papers as a substrate for smoking. This practice poses a significant health risk, as most new analogues will have little safety and toxicity data associated with common abuse routes. Chemical characterization of the potent analogue, salvinorin B ethoxymethyl ether (SB-EME) was performed in order to develop methods of differentiation from Salvia divinorum and salvinorin A. These characterization techniques include HPLC, UV/Vis, NMR, and a colorimetric assay with Ehrlich's reagent. Adulteration of other plant materials with salvinorin A and analogues was performed and analyzed to determine if fortified materials can be detected by colorimetric assay. The validation studies of the HPLC method for SB-EME were found to be accurate (%RE < 12%), precise (RSD = 12%), and linear (R2 = 0.9993) over the mass range of 0.038 µg - 4.8 µg. The LOD was determined to be 0.038 µg, and the LOQ was determined to be 0.113 µg. Significant matrix effects were observed when using Salvia officinalis as a blank matrix, affecting the accuracy and selectivity of the method. However, the purified solutions of SB-EME had baseline resolution from salvinorin A and salvinorin B, which allows for easy qualitative distinction if adulterated samples are suspected. UV/Vis analysis provided a rapid and facile SB-EME characterization method. The UV/Vis trace for SB-EME was distinguishable from both salvinorin A and salvinorin B. NMR analysis confirmed the structures of salvinorin A, salvinorin B and SB-EME, with resonances specific to each compound. The colorimetric assay with Ehrlich's reagent provided a red-orange result with salvinorin B and SB-EME, similar to salvinorin A. While this does not provide differentiation in the field, it does allow all materials related to Salvia divinorum to be identified and collected for further analysis in the lab, as this colorimetric analysis allows easy distinction from common kitchen herbs such as mint, basil, and sage. Characterization of the colored species in the assay with Ehrlich's reagent was performed with UV/Vis, HPLC, and NMR. The UV/Vis analysis showed a new peak at 500 nm in the aqueous layer, which would correspond to a red-orange color. HPLC analysis revealed a new, highly retained peak from the DCM layer of the assay. 1H NMR analysis indicated that the backbone of the salvinorins was not stable in acid, and the molecule that creates the color was likely a degraded analogue. The analysis of the adulterated plant materials by colorimetric assay was inconclusive, as color intensity decreased as concentration of spiked standard increased. HPLC analysis of the vial remnants after the colorimetric assay confirm recoveries of the spiking compounds up to an average of 22% for salvinorin A, 96% for salvinorin B, and 41% for SB-EME over all matrices, indicating incomplete deposition of standard material onto the plant material. In conclusion, salvinorin B ethoxymethyl ether can be detected in the field through the use of Ehrlich's reagent as a colorimetric assay. Further laboratory tests, including HPLC and UV/Vis, were shown to easily distinguish the ether derivative from salvinorin A and B.

This study determined the potential feasibility of surface catalyzed Fenton treatment to remediate soil and groundwater contaminated with bis(2-chloroethyl ether (BCEE), bis(2-chloroethoxy) methane (BCEM), and 1,2-dichloroethane (1,2-DCA) among other contaminants. Parameters that affect the contaminant loss rate such as pH, hydrogen peroxide concentration and solid/water ratio were systematically evaluated. Batch reactors were set-up utilizing either contaminated or uncontaminated soil that was mixed with synthetic groundwater containing the contaminants of interest. The results show an increase in contaminant reduction with a decrease in pH, an increase in hydrogen peroxide concentration, or an increase in the solid/water ratio. For the same set of conditions, contaminant reduction was greater for systems utilizing contaminated soil as compared to the systems containing uncontaminated soil. In addition, specific oxygen uptake rates were measured for an activated sludge exposed to different dilutions of untreated and surface catalyzed Fenton treated water to evaluate whether the residual BCEE, BCEM, and 1,2 DCA as well as their oxidation by products were potentially inhibitory or can potentially serve as a substrate for the activated sludge. The measured specific oxygen uptake rates show that the surface catalyzed Fenton treatment enhanced the biodegradability of the contaminated groundwater and served as a substrate for the activated sludge. / Master of Science

Steroid sulfatase (STS) catalyzes the desulfation of sulfated steroids such as estrone sulfate to the corresponding steroid such as estrone. Inhibitors of STS are believed to have potential for treating estrogen-dependent breast cancer. A new class of potential irreversible suicide inhibitors of STS, based on aryl sulfates bearing a monofluoromethyl or difluoromethyl group ortho to the sulfate group, was synthesized. Key to the success of these syntheses was the use of new sulfation methodology recently developed in the Taylor group. A new and efficient route to 4-formyl estrone, a time-dependent, irreversible STS inhibitor, is also reported. Several new classes of potential, reversible STS inhibitors were synthesized. These compounds are analogs of known STS substrates in which the sulfate group is replaced with an ???,??????-difluoromethylenesulfonamide group, a boronic acid group or a sulfinic acid group. We also report the synthesis of estrone sulfate analogs that bear a carboxylate moiety at the 17-position and a sulfate surrogate at the 3-position. It is anticipated that these compounds will inhibit STS by interacting with Arg98 which lies at the periphery of the active site. Key to the success of this synthesis was the use of the t-butyl group as a protecting group for the 2-position of estrone. Finally, our preliminary investigations into the synthesis of a new class of chiral electrophilic fluorinating agents are presented. These reagents are based on a chiral binaphthyl sulfonimide scaffold and are expected to be capable of performing enantioselective electrophilic fluorinations. Such reagents may be useful in synthesizing organofluorines of biological significance including STS inhibitors.

The recently proposed bioassay procedure that is based on the substrate induced quenching (SIQ) of an indicator fluorescence for the measurement of analyte concentrations is evaluated. In this type of assay a enzynatic reaction and a fluorescence quenching interaction are coupled together. Typically, an appropriate dehydrogenase enzyme reduces or oxidises the nicotinamide adenine dinucleotide cofactor. The change in the concentration of NADH results in variations in the excited fluorophore population as observed through fluorescence intensity. This latter aspect is used to monitor substrate (analyte) concentrations. Results on the investigation of the substrate induced quenching bioassay method and possibilities of using it as the basis of (i) a novel enzyme bioassay technique and (ii) a novel bioprobe format are presented. Ethanol was chosen as the model analyte, and a new assay procedure for its measurement was developed. A generic theoretical relation is discussed for the observed assay kinetics of substrate induced quenching (SIQ) and a model is described that includes the effects due to dynamic/static quenching of the fluorophore by either the enzyme substrate or product. The validity of the derived model is shown by comparison with experimental results for a SIQ based ethanol assay. The option of running the dehydrogenase reaction so as to consume NADH rather than generate it is also investigated. In order to demonstrate this approach acetaldehyde was chosen as the model analyte, and a assay procedure for its measurement was developed. The potential of the SIQ technique for incorporation into biosensor based upon a 'reservoir' format was demonstrated through the development of custom optical instrumentation and resevoir flowcell. Applicability of the SIQ technique to other biosensor formats such as flow-injection analysis and 'dry reagent' technology is discussed. The overall applicability of the SIQ technique is assessed through the generation of a number of SIQ assays on the following substrates: ethanol, glucose, glucose-6- phosphate, L-glutamic acid, isocitric acid, acetaldehyde, pyruvic acid, ot-ketoglutaric acid, and oxalacetic acid.