Indole diterpenoid synthetic studies. Part I. Optimization of the synthetic sequence leading to the eastern hemisphere subtarget of nodulisporic acids A, D, and F. Part II. Construction of the highly strained CDEF parent tetracycle of nodulisporic acids A and B

Chapter one of this dissertation gives an overview of the isolation and structure determination of nodulisporic acids and details their biological activity. Then the optimization of the synthetic sequence leading to the Eastern Hemisphere Subtarget of Nodulisporic Acids A, D and F is described.* Chapter two gives a detailed account of the development of a new modular indole synthesis using a sequential Stille cross-coupling/Buchwald-Hartwig Union/Cyclization tactic. The new modular indole synthesis was successfully applied for the preparation of several highly substituted and strained indoles, including the CDEF parent tetracycle of Nodulisporic Acids A and B.* *Please refer to dissertation for diagrams

Indole diterpenoid synthetic studies. Part I. Optimization of the synthetic sequence leading to the eastern hemisphere subtarget of nodulisporic acids A, D, and F. Part II. Construction of the highly strained CDEF parent tetracycle of nodulisporic acids A and B

Chapter one of this dissertation gives an overview of the isolation and structure determination of nodulisporic acids and details their biological activity. Then the optimization of the synthetic sequence leading to the Eastern Hemisphere Subtarget of Nodulisporic Acids A, D and F is described.* Chapter two gives a detailed account of the development of a new modular indole synthesis using a sequential Stille cross-coupling/Buchwald-Hartwig Union/Cyclization tactic. The new modular indole synthesis was successfully applied for the preparation of several highly substituted and strained indoles, including the CDEF parent tetracycle of Nodulisporic Acids A and B.* *Please refer to dissertation for diagrams

Characteristics of bamboo defects in peapod-grown double-walled carbon nanotubes

Single-walled carbon nanotubes can function as nanoscale reaction chambers for growing smaller nanotubes within the host tube from encapsulated fullerenes by annealing. The diameter of the host outer tube restricts the diameter of the inner tube due to van der Waals interactions but not its chirality: it is possible that inner tubes with different chiralities start to grow in different places at the same time. A straight junction occurs at the connection of these two tubes which we refer to as bamboo defects. We show that localized states appear in the calculated density of states associated with these bamboo defects, some of them close to the Fermi level, and present a detailed theoretical study of ballistic transport through double-walled tubes where the inner shell contains bamboo defects. We find that the presence of bamboo defects should be possible to detect through electronic-transport measurements and the number of bamboo defects per unit length can be extracted from the structure of the resonances appearing in the transmission coefficient

Total Synthesis and Structural Verification of Isatindigotindoline C

Total synthesis of the polycyclic alkaloid isatindigotindoline C is achieved in two steps using an exo-selective [3+2]-dipolar cycloaddition. The synthesis verifies the originally computationally assigned relative stereochemistry

TROUBLESHOOTING BASEL II: THE ISSUE OF PROCYCLICALITY

A widespread concern about Basel II capital requirements is that it might amplify business cycle fluctuations, forcing banks to restrict their lending when the economy goes into recession. Under the IRB approach of Basel II, capital requirements are increasing functions of the probability of default (PD), loss given default (LGD) and exposure at default (EAD) parameters estimated for each borrower, and these inputs are likely to rise in economic downturns. In this paper, we compare two alternative procedures that are designed to somehow moderate the procyclical effects induced by Basel II - type capital regulation. The starting points of our analysis consist Jokivuolla, Kiema and Vesala (2009) and Repullo and Suarez (2009), who both examined the impact of regulatory capital's procyclical effects. It's vital to note remarks of Caprio (2009), that is, making regulatory capital levels countercyclical could worsen the state of an economy during a recession. As we do not have access to the Romanian Central Credit Register database, we compute a model-economy that stands as a proxy for the Romanian firms' sector. Our simulated Romanian economy can be characterised by all Romania-specific macroeconomic controls. Then we estimate a model of PDs during the period 2000 - 2010, and based on the estimated probabilities of default we compute the corresponding series of Basel II capital requirements. After the diagnosis of procyclicality, we analyze two procedures that try to mitigate the cyclical effects of capital regulation: smoothing the output of the Basel II formula, and smoothing the input, by construction of through-the-cycle (TTC) PDs. The comparison of the different procedures is based on the criterion of minimizing the root mean square deviations of each adjusted series. Our results show that the best ways to moderate procyclicality are either to smooth the input of the Basel II formula by using through-the-cycle PDs, or to smooth the output with a multiplier based on GDP growth. We conclude that the GDP-based smoothing may be more efficient than the use of TTC PDs in terms of simplicity and transparency. In terms of the GDP adjustment, regulatory capital levels should increase with approx. 1,31% during an economic growth period and decrease with 4,03% during a recession, in order to mitigate the cyclical effects induced by Basel II - type capital regulation

Arylboronic Acid-Catalyzed C-Allylation of Unprotected Oximes

Unprotected keto- and aldoximes are readily C-allylated with allyl diisopropyl boronate in the presence of arylboronic acid catalysts to yield highly-substituted N-alpha-secondary (2°) and tertiary (3°) hydroxylamines. The method’s synthetic utility is demonstrated with the total synthesis of the trace alkaloid N-methyl-euphococcine. Preliminary experimental and computational mechanistic studies point toward the formation of a boroxine as the active allylating species.<br /

Separation of 2-naphthol atropisomers on cyclofructan-based chiral stationary phases

International audienceA set of fifteen 2-naphthol-derived atropisomers were evaluated on three different cyclofructan-based chiral stationary phases (CSP). The cyclofructan CSPs were a dimethylphenyl-derivatized cyclofructan 7 (CF7-DMP), a isopropyl (CF6-P) and a R-naphthylethyl cyclofructan 6 (CF6-RN) derivative, all bonded to 5-mu m spherical fully porous silica particles packed into three 25cmx4.6mm columns (commercially available as Larihc columns). The 15 atropisomers were analyzed in the normal-phase mode with heptane/alcohol mobile phases. The CF7-DMP column was the most effective partially or fully separating 14 of the 15 compounds (93%). All 15 compounds could be separated by at least one cyclofructan column. Five compounds could be partially or fully separated by all three CSPs. The effect of ethanol, 2-propanol and butanol as 5 and 10% v/v polar modifiers in heptane was studied. A prototype 15cmx4.6mm column packed with superficially porous 2.7 mu m CF6-P bonded particles was tested with the same set of compounds and a standard HPLC system. The increased efficiency and solvent saving were significant

Density of states deduced from ESR measurements on low-dimensional nanostructures; benchmarks to identify the ESR signals of graphene and SWCNTs

Electron spin resonance (ESR) spectroscopy is an important tool to characterize the ground state of conduction electrons and to measure their spin-relaxation times. Observing ESR of the itinerant electrons is thus of great importance in graphene and in single-wall carbon nanotubes. Often, the identification of CESR signal is based on two facts: the apparent asymmetry of the ESR signal (known as a Dysonian lineshape) and on the temperature independence of the ESR signal intensity. We argue that these are insufficient as benchmarks and instead the ESR signal intensity (when calibrated against an intensity reference) yields an accurate characterization. We detail the method to obtain the density of states from an ESR signal, which can be compared with theoretical estimates. We demonstrate the success of the method for K doped graphite powder. We give a benchmark for the observation of ESR in graphene

Catalyst-Free Transfer Hydrogenation of Activated Alkenes Exploit-ing Isopropanol as the Sole and Traceless Reductant

Both metal-catalyzed and organocatalytic transfer hydrogenation reactions are widely employed for the reduction of C=C, C=O and C=N bonds. Described herein is an unconventional catalyst-free transfer hydrogenation reaction of activated al-kenes using isopropanol as an eco-friendly reductant and solvent. The reaction gives convenient synthetic access to a wide range of substituted malonic acid half oxyesters (SMAHOs) in moderate to good yields. Mechanistic investigations point to-wards an unprecedented hydrogen bond-assisted transfer hydrogenation process