Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references (leaves 266-280). Available also in a digital version from Dissertation Abstracts.

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Thesis (Ph. D.)--Virginia Polytechnic Institute, 1966. / Vita. Abstract. Includes bibliographical references (leaves 121-125). Also available via the Internet.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1947. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 167-171).

Thesis--Universität Heidelberg, 1894.

The scope of microwave induced synthesis of various cyclic compounds was investigated and considerably expanded. The advantages of this synthetic method were clearly demonstrated when compared to conventional heating methods of organic synthesis. The exposure of organic compounds to continual Ultraviolet (UV) radiation damages the materials and reduces their chemical and physical properties and in most cases irreversibly and this is not only a concern for industry but for consumers as well. Particularly prevalent are incidences of skin cancer now linked to UV radiation. Research efforts are directed towards finding cheap and efficient UV-absorbers to protect such light sensitive materials. Phenyl salicylates and hydroxybenzophenones constitute families of UV-absorber compounds, and this has necessitated this research. The condensation of differently substituted phenols with salicylic acid, catalyzed by either phosphoric acid (PPA), POCl3/ZnCl2 or ZnCl2 afforded the anticipated phenolic type UV -absorber molecules such as phenyl salicylate, 4-hydroxyphenyl-2-hydroxybenzoate, 2,3-dihydroxyphenyl-2-hydroxyphenylbenzoate, 3-hydroxyphenyl-2-hydroxybenzoate, (2,4-dihydroxyphenyl)(2-hydroxyphenyl)methanone, (2,3-dihydroxyphenyl)(2-hydroxyphenyl) methanone and 1,3-dihydroxyxanthone. PPA proved to be a more efficient catalyst for the condensation of salicylic acid with phenol, hydroquinone, pyrogallol and catechol while POCl3/ZnCl2 gave higher yields for resorcinol and phloroglucinol. In all cases, ZnCl2 alone did not show significant yield enhancement. The second part of this research work describes a convenient one-pot synthesis of NMethyl-2-pyrrolidone (NMP) an important industrial solvent by a conventional heating process and by microwave irradiation. The intermediate N-Methyl-hydroxybutyramide formed from the exothermic reaction of =-butyrolactone with aqueous monomethylamine, underwent an intramolecular condensation reaction catalyzed by highly active copper powder to form the anticipated product in very good yields.

The isomers of cyclo(Trp-Pro) (cyclo(L-Trp-L-Pro), cyclo(L-Trp-D-Pro), cyclo(D-Trp-LPro) and cyclo(D-Trp-D-Pro)) have been successfully synthesized and screened for biological activity. High percentage yields were obtained by using the three phase synthesis system, which involves the synthesis of the intermediate protected linear dipeptides, followed by the removal of the protecting Boc groups. This step is followed by cyclization and crystallization of the isomers. The diketopiperazines rings of cyclo(L-Trp-L-Pro) and cyclo(D-Trp-D-Pro) contain cisamide bonds, while cyclo(L-Trp-D-Pro) and cyclo(D-Trp-L-Pro) contain trans-amide bonds. These bonds govern the conformation of the diketopiperazines ring. The isomers have shown different degrees of biological activity, possibly as a result of the orientation of the side chain of tryptophan and this difference in conformation, leading to varying interactions between isomer and a range of receptors. Under experimental conditions, 10-3 M cyclo(L-Trp-D-Pro) and cyclo(D-Trp-L-Pro) showed effective anticancer activity against the cervical cancer cell line, HeLa, resulting in a <50% reduction in cell viability. Cytotoxicity screening with cyclo(D-Trp-L-Pro) indicated that it was hepatocyte-specific in its toxicity, whilst the other isomers were cytotoxic against the other cell types tested. At 1mg/ml, cyclo(L-Trp-L-Pro) proved to be an effective antimicrobial agent against Gram positive bacteria, while cyclo(L-Trp-DPro) effectively inhibited the growth of the Gram negative bacteria, Esherichia coli. Cyclo(D-Trp-L-Pro) proved to be effective against Streptococcus, while cyclo(D-Trp-DPro) effectively reduced viability of the yeast, Candida albicans. Cyclo(D-Trp-L-Pro) was the only isomer to show Ca2+-channel antagonism, whilst the other isomers resulted in opening of the Ca2+-channel. No effects were observed on K+-channel activity for all the isomers tested. The isomers also proved to be valuable antiarrhythmic agents by effectively reducing the time spent in ventricular tachycardia and arrhythmia, as well as decreasing the time for the heart rate to return to a normal sinus rhythm. Furthermore, cyclo(L-Trp-D-Pro) showed positive chronotropic activity, while cyclo(D-Trp-L-Pro) ii showed negative chronotropic activity. In addition, cyclo(L-Trp-D-Pro) and cyclo(D-Trp- L-Pro) also increased the coronary flow rate. 0.125 –1 mM Cyclo(L-Trp-D-Pro) decreased aggregation in washed platelets induced by thrombin. All isomers increased adhesion to an artificial surface when the platelets were stimulated by ADP, yet caused reduced adhesion when the platelets were stimulated by thrombin. These results prove the potential of these compounds as novel agents in a range of biological fields, indicating that a combination of L- and D- amino acids may prove more effective than an agent consisting solely of L-amino acids.