No description available.

Thesis (doctoral)--Albert-Ludwigs-Universität Freiburg im Breisgau, 2003.

The letter-exchange between Josip Slavenski and Ludwig Strecker, one of the directors and owners of the renowned publishing house 'Schott's Söhne' in Mainz throws light not only on one specific case of the efforts of a composer coming from the European periphery to achieve international recognition, but also on the relations between composers and their publishers in the period between two world wars. This correspondence also reflects the effects that major political events - the most important at the time in Europe being the rise of national-socialism - had on the sphere of culture and music in particular.

De nouveaux β-aminoalcools chiraux ont été synthétisés en 3 à 4 étapes avec de bons rendements globaux (19-42%). Ils ont été testés en tant que ligands dans la réaction de réduction de cétones aromatiques par transfert d’hydrogène. Des excès énantiomériques jusqu’à 91% ont été obtenus avec de bonnes conversions jusqu’à 99%. La réduction asymétrique de cétones aromatique par le borane a été également étudiée. Ces β-aminoalcools se sont montrés actifs mais pas très énantiosélectifs. Ces composés ont également été utilisés en tant que ligands dans la réaction d’addition du diéthylzinc sur des aldéhydes aromatique conduisant aux produits désirés avec de bons rendements (jusqu’à 98%) et de bonnes énantiosélectivités (jusqu’à 80%). En revanche, la réaction d’addition d’autres organométalliques (l’organozincique, le silane, l’étain et le nickel) sur aldéhydes montre de faible énantiosélectivité dans la plupart de cas.Dans la dernière partie de ce travail, un des β-aminoalcools synthétisés a été évalué dans la réaction de cyanation catalytique énantiosélective d’aldimines. Malgré des bonnes conversions obtenues, des faible énantiosélectivités ont été observées. / Chiral β-aminoalcohol compounds were prepared in 3 or 4 steps from isosorbide in good overall yields (19-42%). These compounds were used as ligands in the asymmetric transfer hydrogenation of aromatic ketones giving good enantioselectivities (up to 91% ee) and excellent conversions (up to 99%). The asymmetric reduction of aromatic ketones by borane complexes using these aminoalcohols was also evaluated. Good catalytic activity but low enantioselectivity were observed. Asymmetric addition of diethylzinc to aromatic aldehydes using these β-aminoalcohols was also studied leading to desired products in good yields (up to 98%) and good enantioselectivities (up to 80%). However, no asymmetric induction was observed when using other organometallics (organozinc, silane, nickel, tin).The last part of this work consisted in evaluating one of these β-aminoalcohols in the Titanium-catalyzed asymmetric cyanation of aldimines. Despite good conversions, low enantioselectivities were observed.

No description available.

<p>The class of meteorites called carbonaceous chondrites are examples of material from the solar system which have been relatively unchanged from the time of their initial formation. We investigate the carbonaceous chondrite subclasses CI, CM, CR, CV, and CO, which contain high levels of water and organic material, including amino acids. These subclasses span petrologic types 1 through 3, indicating the degree of internal chemistry undergone by the meteoritic parent body. The goal of this thesis is two-fold: to obtain a comprehensive view of amino acid abundances and relative frequencies in carbonaceous chondrites, and to recreate these patterns via thermodynamic computational models.</p> <p>We collate available amino acid abundance data for a variety of meteorites to identify patterns in total abundance and relative frequencies. We consider only a set of 20 proteinogenic alpha-amino acids created via a specific chemical pathway called Strecker synthesis. We plot abundances of individual amino acids for each subclass, as well as total abundances across all subclasses. We see a predominance in abundance and variety of amino acids in the CM and CR subclasses, which contain concentrations of amino acids greater by several orders of magnitude than other carbonaceous subclasses. These subclasses correspond to an aqueous alteration temperature range of 200 deg. C to 400 deg. C. Within the CM2 and CR2 meteorites, we identify trends in the relative frequencies of amino acids in preparation for computational modeling.</p> <p>Now having a baseline observed amino acid abundance plot, we recreate both the total amino acid abundance pattern as well as the relative frequency of amino acids within the CM2 chondrite subclass using computational models. We use thermodynamic theory of Gibbs free energies to calculate the output of amino acids in a meteoritic parent body assuming chemical equilibrium and some set of initial concentrations of organic material. Our model recreates abundance patterns in the temperature range 200 deg. C to 400 deg. C, ~10⁵ parts-per billion (ppb), and the temperature range 400 deg. C to 500 deg. C, ~10² ppb. Our model does not fit well between temperatures of 150 deg. C to 200 deg. C. Our current model assumes a uniform composition of initial chemical reactants; likely an inhomogeneous composition would be a more accurate physical representation of a parent body. In addition, we match relative frequencies to observed frequencies for each amino acid in the CM2 subclass to well within an order of magnitude.</p> / Master of Science (MSc)

Combined thermodynamic/kinetic events amount to a kinetically controlled Dynamic Combinatorial Resolution (DCR) process, where the lability of themolecules/aggregates are used to generate dynamics, and the species experiencing the lowest activation energy is selected via kinetic process. Bothinter- and intramolecular processes can be performed using this concept,resulting in complete resolution and associated amplification of the selected species. When intermolecular processes are resolved using this method, an additional advantage is that only a catalytic amount of selector is required tocontrol the system.In this thesis, the Henry and Strecker reactions were developed as efficient C–C bond-forming routes to single and multi-level dynamic covalent systems.These methods efficiently provided a vast variety of substrates from smallnumbers of starting compounds. These dynamic systems, generated underthermodynamic control at mild conditions, were coupled in one-pot processes with kinetically controlled lipase-mediated transacylation. The enzym emediated resolution of the dynamic nitroaldol system led to enantiomericallypure β-nitroacetates in high yield. Furthermore, combination of multi-leveldynamic Strecker systems and lipase-mediated acylation resulted in theresolution of specific α-aminonitriles from the pool.In addition, the asymmetric synthesis of discrete β-nitroalkanol derivatives wassimply achieved, resulting in high yields and high enantiomeric purities through the direct one-pot procedure. Moreover, racemase type activity oflipase enzyme through N-substituted α-aminonitrile structure has been discovered. By use of control experiments together with molecular modeling,the mechanism of the racemization process has been established. Asymmetric synthesis of N-methyl α-aminonitriles was also performed through the dualfunction of lipase, resulting in high yield and good enantio selectivity. / <p>QC 20100818</p>