No description available.

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

Cyclic cage compounds have attracted much attention in pharmaceutical studies. The lipophilic nature of these compounds plays an important role in facilitating the crossing of the cellular membranes, including the blood brain barrier (BBB) and the central nervous system (CNS). Several adamantane and pentacyclo[5.4.0.02,6.03,10.05,9]undecane (PCU) derivatives have shown great potential as antiviral, antibacterial and neuroprotective compounds. The aim of this study includes the synthesis of hydantoin derivatives of adamantane and PCU as anticonvulsant compounds. Fosphentoin sodium (Cerebyx) 48 is a commercial anticonvulsant drug. Structurally, compound 51 and 52 are similar to Cerebyx 48, where the two phenyl groups have been replaced with PCU or adamantane skeleton respectively. The cage skeleton should increase the lipophilic character of the drug whilst the phosphate group should retain the water solubility of the substrate. The attempted synthesis of these compounds is described in Chapter 2. The PCU hydantoin is readily converted to the PCU amino acid. The synthesis of the PCU amino acid 41 and its Fmoc derivative 106 is described in Chapter 3. This compound was incorporated into small peptides, namely Ala-Ala-Ala-PCU-Ala-Ala-Ala-Fmoc and Ala-Val- PCU-Ile for future testing as a potential anti-cancer agent. NMR studies of these peptides are also reported. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2008.

A estrutura da DPC (Difenilciclopropenona) e espectro Raman simulado foram obtidos usando os métodos HF (Hartree - Fock) e DFT (Density Functional Theory). Os espectros Raman e IR foram obtidos, e suas medidas experimentais em acetonitrila mostram vibrações em ca. 1630 e 1850 cm-1 na região do est. (C=O). Estes modos apresentam uma mistura entre o est. (C=O) e movimentos do anel de três membros. O modo em ca. 1630 cm-1 apresenta uma intensidade atípica no IR. Em fase gasosa molécula DPC possui um mínimo global com os anéis fenila dispostos simetricamente fora do plano, o sistema possui uma simetria C2. A comparação entre a molécula DPC e seus precursores, CP (CicloPropenona) e DMC (DiMetilCiclopropenona), destaca a semelhança estrutural e vibracional entre o sistema DPC e DMC. O estudo do efeito de solvente é executado, utilizando-se o sistema DMC para mimetizar os resultados observados para o DPC nos solventes, CCl4, n-hexano, clorofórmio, metanol e a mistura CCl4 com metanol. Os resultados teóricos (HF e DFT) apresentam uma boa correlação com os resultados experimentais. / The structure of DPC (DiphenylCycloPropenone), and its simulated Raman spectrum, are obtained using the HF (Hartree-Fock) and DFT (Density Functional Theory). The Raman and IR spectra are obtained, the experimental measurent in acetonitrile shows vibrations at ca. 1630 and 1850 cm-1 in the carbonylic stretching region. These modes show a mixture between the stretching C=O and the three member ring motions. The mode at ca. 1630 cm-1 shows an anomalous intensity in the IR spectrum. The DPC molecule has a global minimum in the gas phase, with the phenyl rings symmetrically out of plane, the system having a C2 symmetry. The comparison betwen DPC and its analogs, CP (Cyclopropenone) and DMC (DiMethylCyclopropenone), highlights the vibrational and structural similarity between DPC and DMC. The study of the solvent effect is carried out using the DMC system to simulate the results observed for DPC in the solvents, CCl4, n-hexane, CCl3H, CH3OH and the CH3OH and CCl4 mixture. The calculations (HF e DFT) show good correlation with the experimental results.

Thesis. 1975. Ph.D.--Massachusetts Institute of Technology. Dept. of Chemistry. / Vita. / Includes bibliographical references. / Ph.D.

Thesis. 1975. Ph.D.--Massachusetts Institute of Technology. Dept. of Chemistry. / Vita. / Bibliography: leaves [95]-99. / by Stephen Koch. / Ph.D.

No description available.

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1991. / Vita. Abstract. Includes bibliographical references (leaves 169-194). Also available via the Internet.

Title from title page of PDF (University of Missouri--St. Louis, viewed March 22, 2010). Non-Latin script record Includes bibliographical references.

The complexation properties of the two isomers of the cyclic polyether dicyclohexyl-18-crown-6 are examined in aqueous solution for a series of metal ions at various reaction temperatures. The results are discussed in terms of size relationships and salvation characteristics of both polyether and metal ions. ΔCp° values are determined from the temperature dependence of the ΔH° values. A discussion of the errors involved in the determination of ΔH° from the temperature dependence of log K values is also included. Comparisons are made between the results of this study and those of a similar study by H. K. Frensdorff, E. I. duPont de Nemours and Co., Wilmington, Delaware, in press. The complexation reactions of dicyclohexyl- and dibenzo-18-crown-6 and benzo-15-crown-5 with Na^+ and K^+ ions are reported in non-aqueous solvents and methanol-water mixtures. The results are discussed with reference to their application in model systems of ion transport. In general the stabilities of the polyether-cation complexes were found to increase with decreasing dielectric constant of the solvent medium. In the methanol-water mixtures large compensating ΔH° and ΔS° changes were observed above 70 weight percent methanol, while the log K values showed a nearly linear increase with increasing methanol concentration. Salvation of the polyethers and metal ions and complexation of ion pairs in non-aqueous solvents are discussed.