(+)-9,10-Dibromocamphor 3̲7̲, prepared in three steps from (+)-3-e̲n̲d̲o̲-bromocamphor 1̲5̲a̲, was found to undergo facile ring cleavage to provide the cyclopentanoid ring systems 1̲5̲8̲, 1̲5̲9̲ and 1̲6̲1̲. The bromoacid 1̲5̲9̲ was readily lactonised to provide 1̲6̲0̲ in high yield. The hydroxyacid 1̲6̲1̲ was converted into the hydrindenone 1̲9̲0̲ in three steps and a further six steps were required to complete the total enantiospecific synthesis of (-)-estrone e̲n̲t̲4̲1̲. Studies directed toward the synthesis of vitamin D₃ (2̲1̲3̲) and metabolites have shown that diastereoselective alkylation of lactone 1̲6̲0̲ and ester 2̲8̲3̲ (derived from 1̲6̲1̲) can be accomplished in high yield and with almost complete stereoselectivity. As a result, diol 3̲2̲2̲, representing the structural sub-unit of ring D and side chain of vitamin D₃, has been synthesised. Ring cleavage of the bromoketone 3̲5̲0̲ (derived from 1̲5̲9̲) gave 3̲5̲2̲ which was transformed into the aldehyde 3̲3̲2̲ and the trienols 3̲4̲0̲a̲ and 3̲4̲0̲b̲ to complete a formal synthesis of 3̲2̲7̲a̲, one of the components of the California Red Scale pheromone. Methylation of camphor 1̲0̲ yielded the 3-e̲x̲o̲-methyI derivative 3̲6̲2̲b̲ as the major product. The thermodynamically most stable epimer was found to be 3-e̲n̲d̲o̲-methylcamphor 3̲6̲2̲a̲. In contrast, 3-methylcamphor 3̲6̲2̲a.̲b̲ undergoes preferential endo alkylation. The factors governing these results are discussed. (+)-3- e̲n̲d̲o̲-Bromocamphor 1̲5̲a̲ and (+)-3- e̲n̲d̲o̲-9-dibromocamphor 1̲8̲a̲ were found to rearrange to provide (-)-6- e̲n̲d̲o̲-bromocamphor 1̲7̲2̲ and (-)-6- e̲n̲d̲o̲-9-dibromocamphor 2̲6̲. Dehalogenation of 1̲7̲2̲ provided optically pure (-)-camphor e̲n̲t̲1̲0̲ while dehydrohalogenation gave (+)-5,6-dehydrocamphor 1̲7̲3̲.[formula omitted] / Science, Faculty of / Chemistry, Department of / Graduate

This thesis is concerned with an approach to the synthesis of the C/D ring system and side chain of steroids with 11-oxygen functionality. (+)-9,10-Dibromocamphor (18) [prepared in three steps from (+)-endo-3-bromocamphor (4)] was converted to the diester 144 in six steps. The diester 144 underwent a modified acyloin reaction to provide the silylated enediolate 154. A novel methanolysis of the acyloin intermediate 154 gave a 1:1 mixture of the isomeric tricyclic methoxy-ketones 168 and 176. Oxidative cleavage of these methoxyketones 168 [Formula Omitted] and 176 provided the isomeric aldehydes 178 and 180 which were then transformed into the corresponding isomeric esters 181 and 182. This represents a synthesis of the C/D ring system of steroids with 11-oxygen functionality and establishment of the correct absolute stereochemistry at C(13) and C(17). [Formula Omitted] / Science, Faculty of / Chemistry, Department of / Graduate

Camphor has been functionalized at the C-(8) position by treating (+)-3,3-dibromocamphor with bromine and chlorosulphonic acid. A mechanistic rationalization is proposed for this transformation which accounts for the presence of the minor side products that form during 8- and 9-bromination. (+)-8-Bromo-camphor produced by this method was subsequently used as a key intermediate in sesquiterpenoid synthesis. Approaches to the synthesis of both the longicamphane and picrotoxane carbon frameworks are discussed. Our approach to the synthesis of the longicamphane framework involved intramolecular Michael-addition of 9-oxocampherenone. While investigating a proposed synthesis of 9-oxocampherenone via Meyer-Schuster rearrangement of 8-(3-hydroxy-3-methyl-l-butynyl)camphor ethylene acetal an interesting new reaction occurred providing the polycyclic ring system (+)-6,7-dimethyl-6-(l-oxo-2-methylpropyl)tricycle [4 • 2 • 1 • 0³ ' ⁷] nonan-9-one whose structure was determined by X-ray erystallographic analysis. A mechanism for its formations is proposed. Attempts to synthesize 9-oxocampherenone by allylic oxidation of 9-hydroxycam-pherenone and its ethylene acetal derivative are also discussed. Our synthetic approach to the picrotoxane framework involves Baeyer-Villiger oxidation-translactonization of a suitable copacamphor-type derivative. In our first approach the attempted synthesis of 4-hydroxycopacamphor via intramolecular epoxide cyclization of 8-(1,2-epoxy-3-methylbutyl)camphor provided the tricyclic ketol 1,6-dimethyl-4-(l-hydroxy-2-methylpropyl)tri-cyclo [4 • 3 • 0 • 0³ ' ⁷] nonan-2-one . This 5-membered ring cyclization product was formed exclusively during the reaction. The strategy was revised to exclude 5-membered ring formation; the cyclization would be performed on 8-acetoxycampherenone epoxide. The synthesis of 8-acetoxycampherenol methyl ether is discussed and its potential conversion to 8-acetoxycampherenone epoxide is described. / Science, Faculty of / Chemistry, Department of / Graduate

Chiral monoterpenes such as camphor have been widely used in the development of asymmetric catalysts with varying degrees of success. Pyridyl N-donor ligands derived from camphor have been extensively studied and have proven to be very successful. C3 pendant pyridyl alcohol ligands have been neglected until this study. Herein the synthesis of a series of six novel C3 pendant ligands is described. The ligands were synthesised in six steps (seven for ligand 4) using R-(+)-camphor as the starting material. Two alternative methods for the synthesis were investigated with the second method (Method B) proving to be superior. Several difficulties with regards to regioisomers and diastereomers were overcome in establishing the procedure for the synthesis of the ligands. The final compounds were successfully synthesised in moderate yields with absolute regio- and stereo-control. The ligands were evaluated as chiral catalysts in a series of different reactions. The first of these was the alkylation of a series of aldehydes using diethylzinc. This reaction was investigated in order to compare the efficacy of the novel compounds to previous camphor derived pyridyl alcohol ligands. All previous molecules of this type have been evaluated as catalysts in this reaction with varying degrees of success. The novel ligands successfully catalysed this reaction with moderate to good enantioselectivity (up to 85% ee). The results obtained showed these compounds to be significantly superior to a previous analogous C2 pendant β-amino alcohol reported in literature. The results were also comparable to other camphor derived pyridyl alcohol ligands reported previously. The synthesis of ligands 1-4 as well as their evaluation as catalysts in the alkylation of aldehydes with diethylzinc is discussed in detail in chapter 2 (Paper 1). The second reaction in which the ligands were evaluated was the Henry (Nitroaldol) reaction. This reaction has not seen many camphor derived ligands applied as catalysts. Two additional derivatives (5-6) were synthesized and all the compounds were screened as catalysts in this reaction. The ligands successfully catalyzed the reaction with good to excellent yields but only moderate selectivity (up to 56% ee). The details of this evaluation are discussed in chapter 3 (Paper 2). The final reaction in which the ligands were evaluated was the Diels-Alder reaction of 2- acrolyloxazolidinone with cyclopentadiene. The reaction was again successfully catalysed in moderate to good yields with good endo:exo selectivity but fairly poor stereoselectivity (up to 43% ee). Computational models of the proposed complexes were developed in order to explain the poor observed selectivity. The details of this study are reported in chapter 4 (Paper 3). Chapter 5 (Paper 4) involves a NMR and computational investigation of some of the ligands. Complete NMR elucidation using 2D NMR techniques were carried out for the selected ligands. Optimisation of the ligands using high level DFT calculations was carried out in order to aid in the visualisation of potential through space interactions within each molecule. / Thesis (Ph.D.)-University of KwaZulu-Natal, 2009.

Thesis (Ph. D.)--Ohio state University, 1926. / Autobiography. Bibliography: p. 22.

Thesis (Ph. D.)--Ohio state university, 1926. / Autobiography. Bibliography: p. 22.

by Tsoi Yeung-pang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaves 105-106). / Chapter I. --- Acknowledgements --- p.i / Chapter II. --- Abstract --- p.ii / Chapter III. --- Table of contents --- p.iv / Chapter IV. --- List of Tables and Figures --- p.v / Chapter Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Modes of chromatography / Chapter 1.2 --- Objective of the present study / References / Chapter Chapter 2. --- Instrumentation and theory --- p.8 / Chapter 2.1 --- Instrumentation of HPLC / Chapter 2.2 --- Theory of liquid chromatography / References / Chapter Chapter 3. --- Determination of citrate in pharmaceutical preparations by HPLC using indirect photometric detection --- p.21 / Chapter 3.1 --- Introduction / Chapter 3.2 --- Review of the analytical methods / Chapter 3.3 --- Theory of detection / Chapter 3.4 --- Experimental / Chapter 3.5 --- Results and discussion / Chapter 3.6 --- Conclusion / References / Chapter Chapter 4. --- Determination of camphor and menthol by HPLC using indirect conductometric detection --- p.74 / Chapter 4.1 --- Introduction / Chapter 4.2 --- Review of the analytical methods / Chapter 4.3 --- Theory of detection / Chapter 4.4 --- Experimental / Chapter 4.5 --- Results and discussion / Chapter 4.6 --- Conclusion / References

No description available.

Thesis (M.Sc. (Chemistry)) - Rhodes University, 2007.

Mémoire : Sciences : Paris, Faculté des sciences : 1832. / Titre provenant de l'écran-titre.