S’han sintetitzat quatre alquil i aril (9 anthry1) carbinol (metil, fenil isopropil, terc-butil, i) que van revelar la rotació restringida al voltant de l'enllaç C9-C11. La seva energia lliure d'activació per a la rotació s'ha determinat, sent 11.0, 14.0, 21.7, i 9.8 kcal / mol, respectivament. Es descriuen l’aplicació mètodes de mesura del NOE i del temps de relaxació per a la determinació de l'energia d'activació per a la rotació de bons. El bon acord amb els valors obtinguts amb el mètode de la temperatura de coalescència confirma que l'enfocament basat NOE és una bona alternativa per a la determinació de les elevades barreres de rotació. Els càlculs de Mecànica Molecular (MM2) donen valors propers als experimentals. S’han preparat els carbamats homoquirals del 9-anthryl-terc-butylcarbinol i s’ha estudiat el seu equilibri conformacional. La configuració absoluta es va determinar mitjançant la comparació de les dades de RMN amb càlculs de MM. Els enantiòmers de l'alcohol es van obtenir després de la separació cromatogràfica dels derivats de carbamat i la seva hidròlisi. Els alcohols homoquirals van ser preparats per columna de cromatografia quiral directa. S’han detectat i o separat a temperatura ambient els confòrmers cisoid i transoid del 9,10 dipivaloylantracè i del 9,10-bis(1-imino-2,2-dimetilpropil)antracè. La transformació entre dues atropisómers va ser estudiada per RMN i modelat pels mètodes de MM. La difracció de raigs X es va realitzar per als derivats imino. El 9-antril-terc-butilcarbinol es va provar com a agent de solvatació quiral (CSA) en presència de formes racèmica de p-toluenesulfinate de mentil, 9-(1-amino-2,2- dimetilpropil)-9,19-dihydroantracè, àcid R-methoxyfenylacetic i 1-phenyl-1,2- ethanediol. Es formaren els complexes diastereòmers entre el reactiu quiral i cada enantiòmer d'aquests últims compostos. Un dels enantiòmers de 9-antril-tertbutylcarbinol va ser estudiat mitjançant NOE intermolecular i càlculs de dinàmica molecular. Es trobaren les principals diferencies termodinàmiques i estructurals. / Se han preparado Cuatro alquil- y aril- (9-antril)carbinols (metil, isopropil, tert-butil, y fenil) y mostraron la rotación restringida del enlace de C9-Cll. Su energía libre de activación para la rotación ha sido determinada, siendo 11.0, 14.0, 21.7, y 9.8 kcal/mol, respectivamente. Hemos determinado la energía de activación para la rotación de enlace C9-C11 por la aplicación de medidas de NOE y de tiempo de relajación. El buen acuerdo con los valores obtenidos con el método de temperatura coalescencia confirma que el método basado en el NOE es una buena alternativa para la determinación de barreras de rotatorión altas. La Mecánica Molecular (MM2) da valores cercanos a los experimentales. Se ha preparado el carbamato homochiral de 9-antril-tert-butilcarbinol y se ha estudiado su equilibrio conformacional. La configuración absoluta fue determinada por la comparación de los datos NMR con cálculos de MM. Los enantiomers del alcohol fueron obtenidos después de la separación cromatográfica de los carbamatos y tres su hidrólisis. Los mismos alcoholes se obtuvieron a través de una columna HPLC quiral Se han detectado o separado, a temperatura ambiente, los confórmeros cisoide y transoide del 9,10 dipivaloylantraceno y del 9,10-bis(1-imino-2,2- dimetilpropil)antraceno. La transformación entre los dos atropoisómeros se estudió por RMN i se modeló por métodes de MM. La difracción de rayos X se realitzó con los derivados imino. Se ha probado el 9-anthryl-tert-butylcarbinol como agente solvatación chiral (CSA) en presencia de las formas de racemicas de p-toluenesulfinato de mentilo, 9-(1-amino-2,2- dimetilpropil) - 9,19-dihydroanthracene, ácido de R-methoxyphenylacetic y 1-phenyl- 1,2-ethanediol. Se formaron los complejos diastereoisómericos el reactivo quiral y cada enantiomer de estos últimos compuestos. Uno de los enantiomers de 9-anthryltertbutylcarbinol fue estudiado por medio de NOE intermolecular y cálculos de dinámica moleculares. Las diferencias termodinámicas y estructurales principales fueron encontradas. / Four alkyl- and aryl-(9-anthry1)carbinols (methyl, isopropyl, tert-butyl, and phenyl) were synthesized and revealed restricted rotation about the C9-Cll bond. Their free energy of activation for rotation has been determined, being 11.0, 14.0, 21.7, and 9.8 kcal/mol, respectively. The application of NOE enhancement and relaxation time measurements for the determination of the activation energy for bond rotation is described. The good agreement with the values obtained with the coalescence temperature method bears out that the NOE based approach is a good alternative for the determination of high rotational barriers. Molecular Mechanics (MM2) calculations give values close to the experimental ones. The homochiral carbamates of 9-anthryl-tert-butylcarbinol were prepared and their conformational equilibrium was studied. The absolute configuration was determined by comparison of the NMR data with MM calculations. The enantiomers of the alcohol were obtained after chromatographic separation of carbamate derivatives and their hydrolysis. The same homochiral alcohols were prepared by direct chiral column chromatography Cisoid and transoid conformations of 9,10-dipivaloylanthracene and 9,10-bis(1-imino- 2,2-dimethylpropyl) anthracene were separated and detected for the former and isolated for the latter at room temperature. The transformation between two atropisomers was studied by NMR and modeled by MM methods. X-ray diffraction was performed for the imino derivatives. The 9-anthryl-tert-butylcarbinol was tested as a chiral solvating agent (CSA) in the presence of racemic forms of mentil-p-toluenesulfinate, 9-(1-amino-2,2- dimethylpropyl)-9,19-dihydroanthracene, R-methoxyphenylacetic acid and 1-phenyl- 1,2-ethanediol. Diastereomeric complexes were found to form between each enantiomer of these last two compounds. One of the enantiomers of 9-anthryltert-butylcarbinol was studied by means of intermolecular NOE and molecular dynamics calculations. Major thermodynamic and structural differences were found.

No description available.

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.

Heavy ions are collided at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) in an effort to create a unique state of nuclear matter, where quarks and gluons can freely move over volumes larger than the typical size of a nucleon (typical scale of Quantum Chromodynamics, QCD). In this state, called a "Quark Gluon Plasma" (QGP), it is proposed Chiral symmetry is restored. The fact that Chiral symmetry is a symmetry of the Standard model and is broken at low energy (current energy scale of universe) makes the study of its possible very interesting. The analysis in this dissertation searches for signatures of chiral symmetry restoration at the phase transition between the QGP and the hadronic gas phase by using resonance particles as probes. Resonances may decay inside of hot dense matter due to their short lifetimes, and therefore their decay daughters carry away dynamical information such as the mass and decay width. Mass shift and width broadening are predicted signatures of chiral symmetry restoration. The [phi](1020) resonances reconstructed from the dielectron decay channel are investigated in this dissertation. This decay channel does not suffer scattering from the late hadronic medium due to the relatively small interaction cross section of leptons with hadrons. The disadvantage of this channel comes from the small branching ratio. Therefore, large statistics and clean Particle IDentification (PID) are necessary for this analysis. Those requirements were fulfilled with high luminosity beams at RHIC and the newly developed and installed Time Of Flight (TOF) detectors, which provide clear particle identification up to momentum of 2-3 GeV/c, as well as the large acceptance of the Solenoidal Tracker At RHIC (STAR) detector. In this dissertation, measurements of mass, width, transverse momentum spectrum, and yields of [phi][right arrow] e⁺e⁻ at mid-rapidity [mathematical symbols] from the STAR experiment in Au+Au collisions at [mathematical symbols]=200 GeV are presented and compared to a previously measured [phi] meson result from a hadronic decay channel. The possibility of medium modification which implies Chiral symmetry restoration is discussed. / text

In chapter 1 the principles behind circular dichroism spectroscopy and exciton coupled circular dichroism spectroscopy are outlined, and examples are cited that illustrate the utility of these methods in the determination of absolute configuration and ee of chiral amines. This provides background and context for this thesis, which mostly pertains to the sensing of chirality in amines. An exciton coupled circular dichroism method based on the induction of helical chirality in an organometallic host for sensing chiral amines is presented in chapter 2. The method can be used to determine absolute configuration by relating the sign of the first Cotton effect of the host-amine complex to the handedness of the amine. Analysis of the primary circular dichroism optical data is by principal component analysis allows for differentiation of the analytes based on their idendity and handedness. A novel circular dichroism method for detecting chiral amines is discussed in chapter 3. The method uses a highly efficient derivatization method to convert the primary amine into a bidentate imine. Three equivalents of the imine are then assembled together by coordination to Fe(II). The proximity and chiral orientation of the imines leads to exciton coupled circular dichroism, which is of utility in the determination of absolute configuration. Additionally, there is a metal-to-ligand charge transfer band in the visible region that can be used to develop calibration curves, which allow for the determination of the enantiomeric excess of unknown samples with an absolute error of ±5%. Chapter 4 details another imine based circular dichroism method for chiral amines. The method uses a commercially available aldehyde, Fe(II), and circular dichroism spectrometry to sense chirality in amines. It is shown that the circular dichroism signals in the ultraviolet spectrum vary predictably with the handedness of the chiral amine, which has potential applications in the determination of absolute configuration. By developing calibraton curves, signals in the visible spectrum can be used to determine enantiomeric excess with an absolute error of ±6%. Analyzing the primary circular dichroism optical data with linear discriminant analysis allows for differentiation between amines based on their identity and handedness. Finally, chapter 5 illustrates the potential of using the thermodynamic parameters of partitioning between water and octanol as a predictive tool for estimating the contributions of hydrophobicity to host-guest binding events. This is done by showing a relationship between the thermodynamics of partitioning and thermodynamics of hydrophobic binding events for a series of guests and cyclodextrin. A plot of the thermodynamic parameters of binding of a variety of guests to cyclodextrin as a function of the thermodynamic parameters of partitioning between water and octanol shows a linear relationship for a series of alcohols. / text

Pseudoephedrine is well established as a chiral auxiliary in the alkylation of amide enolates to form tertiary and quaternary carbon stereocenters. However, due to its facile transformation into the illegal narcotic methamphetamine, pseudoephedrine is either illegal or highly regulated in many countries, which limits its use in academic and industrial settings. To address this issue, pseudoephenamine has been developed as a replacement for pseudoephedrine in organic synthesis. This new auxiliary suffers no regulatory issues and exhibits several practical advantages over pseudoephedrine, including the high diastereoselectivities observed in alkylation reactions forming quaternary carbon stereocenters, the propensity for pseudoephenamine amides to be free-flowing crystalline solids, and the sharp, well-defined peaks that typically compose the 1H NMR spectra of these amides. / Chemistry and Chemical Biology

A polymer photodetector is fabricated using polythiophene with chiral alkyl side chains. The Cotton effect is observed in the CD spectrum of the photodetector, indicating an unequal absorbance of left- and right-handed circular polarized light (CPL). The photodetector is proven to be able to identify incident left- and right-handed CPL. Polymer photodetectors that are made from R- and S-limonene induced achiral polymers are fabricated. A “hot spin-coating” process is introduced to cast uniform limonene induced polymer films. As a result of chirality transfer, Cotton effects are also observed in these photodetectors’ CD spectra. A model is suggested to explain the chirality generation of the polythiophene with chiral alkyl side chains and limonene induced achiral polymers. / Thesis (Master, Chemistry) -- Queen's University, 2014-03-25 14:37:23.168

En el curso de esta Tesis Doctoral, se sintetizaron librerías de (1,2)-diaminas enantiopuras y 2,2’-bifenoles pro-quirales. La transferencia de quiralidad desde la diamina al bifenol, mediante puentes de hidrógeno o coordinación a un metal (ZnII, CuII), fue demostrada por dicroísmo circular (DC). El comportamiento en disolución de los complejos supramoleculares (usando puentes de hidrógeno), así como sus constantes de asociación, fue estudiado mediante valoraciones de RMN, UV-vis y ITC. La determinación de las configuraciones absolutas de los complejos de ZnII se consiguió mediante la resolución de las estructuras de rayos-X y los estudios de DC, tanto a un nivel teórico como experimental. Un nuevo ligando fosforado, potencialmente catalítico, fue preparado a partir de 2,2’-bifenol, mostrando el camino para el desarrollo de nuevos catalizadores supramoleculares. / During the course of the thesis libraries of chiral (1,2)-diamines and prochiral 2,2’-biphenol derivatives were synthesised. The transfer of chirality from the diamine to the biphenol moiety mediated either by hydrogen bonding or coordination to a metal centre (ZnII, CuII) was demonstrated by CD (circular dicroism). The behaviour in solution of the hydrogen bonded complexes was investigated by NMR spectroscopy, UV-vis and ITC titrations (determination of association constants. The determination of absolute configurations of the ZnII complexes was achieved by X-ray structure determination and CD analyses both on the experimental and theoretical level. Last but not least, a new potentially catalytic phosphane ligand was derived from a dynamically racemic 2,2’-biphenol derivative.

The Whelk-O1 chiral stationary phase is widely used in liquid and supercritical chromatography for the separation of enantiomers. The enantioselective mechanism of the Whelk-O1 chiral stationary phase is the main focus of this thesis. Semi-flexible models are developed based on ab initio calculations for the Whelk-O1 selector and a series of chiral analytes. Extensive molecular dynamics simulations are then applied to study the solvation, selectivity and in silico optimization of the chiral stationary phase. The solvation of the Whelk-O1 chiral stationary phase has been explored in a normal phase n-hexane/2-propanol solvent, a reversed phase water/methanol solvent, and a supercritical CO2/methanol solvent. We found that, in all three solvents, the Whelk-O1 selectors are open to the bulk, indicating readiness for docking of analyte. Significant solvent partitioning at the interfaces was noticed, which generates a polarity gradient between the stationary phase and the bulk, and may encourage a high analyte concentration at the interface. Hydrogen bonding activities on the amide hydrogen, amide oxygen, and nitro oxygen of the Whelk selector have also been analyzed. The selectivity of the Whelk selector was studied by molecular dynamics simulations of analyte docking on the chiral stationary phase. The elution orders and the separation factors for a series of analytes were predicted successfully. We found that hydrogen bonding and π-π stacking interactions are essential for the enantioselectivity as they are strong and specific, and they hold analytes to the cleft region of the Whelk selector. Other interactions, both stabilizing interactions such as the CH-π interaction and the edge-to-face π-π interaction, and destabilizing interactions such as steric hindrance and unfavorable conformational changes also contribute to the enantioselectivity. We identified a dominant docking arrangement for the most retained enantiomers. Other docking arrangements were found to be more frequent for the least retained enantiomers and these involve interactions with alternative selector sites. Based on the identified enantioselective mechanism obtained from the study, an optimization of the Whelk-O1 chiral stationary phase was undertaken and in silico evaluation of the modified chiral stationary phases was carried out. It was demonstrated that restriction of the alternative docking arrangements for the least retained enantiomers could possibly improve the enantioselectivity of the chiral stationary phase. / Thesis (Ph.D, Chemistry) -- Queen's University, 2008-10-08 11:54:20.249

Biocatalysts are increasingly prevalent in the large-scale synthesis of enantiomerically pure compounds. However, many sought-after reactions lack a suitable enzymatic production route. This work describes the development of a novel amine dehydrogenase through the application of directed evolution altering the substrate specificity of an existing leucine dehydrogenase scaffold. Eleven rounds of directed evolution completely altered the enzyme’s specificity and successfully created amination activity. The resulting amine dehydrogenase asymmetrically catalyzes methyl isobutyl ketone and free ammonia to 1, 3-dimethyl butyl amine. The enantioselectivity of the wild-type enzyme was maintained despite the drastic changes to the binding pocket and yielded (R)-1,3-DMBA with nearly complete conversion making it an attractive catalyst in the synthesis of chiral amines. This was the first example of a cofactor-dependent amine dehydrogenase capable of selectively synthesizing chiral amines from a prochiral ketone and free ammonia. Additionally, knowledge gained altering the specificity of the leucine dehydrogenase scaffold was applied to an analogous phenylalanine dehydrogenase scaffold allowing for rapid evolution of novel activity. A single mutational library resulted in a second amine dehydrogenase with enhanced activity toward significantly different substrates, while maintaining comparable conversion and enantioselectivity. These two scaffolds provide examples of the broad applicability of the identified mutations in creating amine dehydrogenase activity.