Stereoselective modification of N-(α-Hydroxyacyl)-Glycine esters via palladium-catalyzed allylic alkylation and studies toward the total synthesis of Callipeltin A and C

This PhD thesis describes the development of a novel method for palladium-catalyzed allylic alkylation of titanium chelated enolates of N-(α-Hydroxyacyl)-glycine esters. The reaction could be performed with a variety of allylic electrophiles and generally proceeds with high stereoselectivity. A multitude of functional groups is tolerated such as halogenides or vinyl stannanes, which allows for subsequent modification of the side chain. By choice of reaction conditions, both diastereomers are accessible in a selective fashion. The second part of this thesis describes the effort toward the first total synthesis of the natural products callipeltin A and C. These complex depsipeptides contain a multitude of non-proteinogenic amino acids and a rare terminal hydroxy acid. During this project, several stereoselective approaches toward the amino acid and hydroxy acid building blocks could be developed. The research culminated in the development of a route toward the cyclic heptapeptide core of callipeltin A and the synthesis of a protected version of callipeltin C. However, the coupling of the peptide core with the side chain was unsuccessful and the final deprotection of the benzyl amide group proved impossible. While the total synthesis was ultimately unsuccessful, this thesis described an unprecedented synthetic route toward callipeltin C precursors. This route should allow for straightforward access to the natural product by slight variations in the protection group strategy.Die vorliegende Doktorarbeit beschreibt die Entwicklung einer neuen stereoselektiven Methode der Palladium-katalysierten allylischen Alkylierung. Als Nukleophile fungieren hierbei Titan-chelatisierte Enolate von N-(α-Hydroxyacyl)-glycinestern welche mit einer Vielzahl an allylischen Elektrophilen umgesetzt werden konnten. Die Methode toleriert dabei eine Reihe an funktionellen Gruppen wie Halogenide oder Vinylstannane, wodurch die nachträgliche Funktionalisierung der Seitenkette ermöglicht wurde. Durch die Wahl der Reaktionsbedingungen ist der selektive Zugang zu beiden Diastereomeren möglich. In einem weiteren Projekt wurde eine Syntheseroute für die Depsipeptide Callipeltin A und C untersucht. Im Rahmen dieses Projekts gelang die Entwicklung neuer asymmetrischer Synthesen für die Aminosäure und Hydroxysäure Bausteine der Callipeltine. Die einzelnen Bausteine wurden nachfolgend durch sukzessive Peptidknüpfungen miteinander verkuppelt. Dabei gelang die Synthese des Peptidkerns in exzellenten Ausbeuten, allerdings scheiterten jegliche Versuche der Knüpfung des cyclischen Depsipeptids mit der Seitenkette. Eine leichte Variation der Strategie ermöglichte zudem die Synthese eines vollständig geschützten Derivats von Callipeltin C. Im Rahmen der globalen Entschützung erwies sich die Spaltung der letzten Benzyl Schutzgruppe jedoch als unmöglich. Die Totalsynthese der beiden Naturstoffe gelang somit nicht, jedoch konnte eine robuste Strategie entwickelt werden, welche den Zugang zu dem geschützten Naturstoff in guten Ausbeuten erlaubt. Durch die Wahl einer alternativen Schutzgruppe sollte die vorliegende Syntheseroute somit die erste Totalsynthese von Callipeltin C ermöglichen

Jump Rope Vortex in Liquid Metal Convection

Understanding large scale circulations (LSCs) in turbulent convective systems is important for the study of stars, planets and in many industrial applications. The canonical model of the LSC is quasi-planar with additional horizontal sloshing and torsional modes [Brown E, Ahlers G (2009) J. Fluid Mech. 638:383--400; Funfschilling D, Ahlers G (2004) Phys. Rev. Lett. 92(19):194502; Xi HD et al. (2009) Phys. Rev. Lett. 102(4):044503; Zhou Q et al. (2009) J. Fluid Mech. 630:367--390]. Using liquid gallium as the working fluid, we show via coupled laboratory-numerical experiments that the LSC in a tank with aspect ratios greater than unity takes instead the form of a "jump rope vortex", a strongly three-dimensional mode that periodically orbits around the tank following a motion much like a jump rope on a playground. Further experiments show that this jump rope flow also exists in more viscous fluids such as water, albeit with a far smaller signal. Thus, this new jump rope mode is an essential component of the turbulent convection that underlies our observations of natural systems

noteEd - A web-based lecture capture system

Electronic capture and playback of lectures has long been the aim of many academic projects. Synote is an application developed under MACFoB (Multimedia Annotation and Community Folksonomy Building) project to synchronise the playback of lecture materials. However, Synote provides no functionality to capture such multimedia. This project involves the creation of a system called noteEd, which will capture a range of multimedia from lectures and make them available to Synote. This report describes the evolution of the noteEd project throughout the design and implementation of the proposed system. The performance of the system was checked in a user acceptance test with the customer, which is discussed after screenshots of our solution. Finally, the project management is presented containing a final project evaluation

On the efficiency of Hamiltonian-based quantum computation for low-rank matrices

We present an extension of Adiabatic Quantum Computing (AQC) algorithm for the unstructured search to the case when the number of marked items is unknown. The algorithm maintains the optimal Grover speedup and includes a small counting subroutine. Our other results include a lower bound on the amount of time needed to perform a general Hamiltonian-based quantum search, a lower bound on the evolution time needed to perform a search that is valid in the presence of control error and a generic upper bound on the minimum eigenvalue gap for evolutions. In particular, we demonstrate that quantum speedup for the unstructured search using AQC type algorithms may only be achieved under very rigid control precision requirements.Comment: 17 pages, no figures, to appear in JM

MICROSTRUCTURING IN PLATINUM AND STAINLESS STEEL MATERIAL USING PICOSECOND Nd:YAG LASER

The number of products manufactured in micro- and nano-size is increasing every year. In electronics, medicine, biology and other industries, because of the rapid development of technologies, is possible to produce new or already used products in very small sizes, maintaining or even improving the efficiency of the product or giving an opportunity to use them for new purposes. Currently available pico- and femtosecond lasers ensure the production of such products in very small sizes. In this study, the treatment of platinum and stainless steel using a picosecond Nd:YAG laser with a wavelength of 1064nm, was considered. The obtained results for the laser ablation process of these materials will be useful for further research in the field of laser microprocessing

Covering triangular grids with multiplicity

Motivated by classical work of Alon and F\"uredi, we introduce and address the following problem: determine the minimum number of affine hyperplanes in $\mathbb{R}^d$ needed to cover every point of the triangular grid $T_d(n) := \{(x_1,\dots,x_d)\in\mathbb{Z}_{\ge 0}^d\mid x_1+\dots+x_d\le n-1\}$ at least $k$ times. For $d = 2$, we solve the problem exactly for $k \leq 4$, and obtain a partial solution for $k > 4$. We also obtain an asymptotic formula (in $n$) for all $d \geq k - 2$. The proofs rely on combinatorial arguments and linear programming.Comment: 23 pages, 3 figure

Draft Genome Sequences of Chlamydiales Bacterium STE3 and Neochlamydia sp. Strain AcF84, Endosymbionts of Acanthamoeba spp.

Chlamydiales bacterium STE3 and Neochlamydia sp. strain AcF84 are obligate intracellular symbionts of Acanthamoeba spp. isolated from the biofilm of a littoral cave wall and gills from striped tiger leaf fish, respectively. We report the draft genome sequences of these two environmental chlamydiae affiliated with the family Parachlamydiaceae