Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Nebraska, 1933. / Bibliography: p. 18.

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A number of 14-membered lactones, derived from 42 or 43 were used to investigate a series of alkylation, hydride reduction and hydrogenation reactions. These reactions yielded diastereoselective product distributions which were rationalized as proceeding through a [3434] conformation. A simple model for determining these low energy conformations was developed using MM2 calculations, energy trends of acyclic molecules, X-ray crystallography and NMR spectroscopy. In order to unambiguously identify ring conformations, a method to generate polar maps of the large ring lactones was developed. These polar maps quickly differentiated complex ring conformations as well as identifying the symmetry elements of a conformation. With the aid of polar maps, a new solid state conformation for 14-membered rings was discovered for two macrolides synthesized in this project. Furthermore, three additional unidentified examples of this conformation were recognized from the literature. Energy calculations showed this twisted conformation to be of very low energy. The discovery of the twist conformation led to an improved nomenclature for large rings which considers the number of bonds separating both corner and pseudo corner atoms. Under this proposed nomenclature, the twist conformation was designated the [34'3'4'] conformation. During this investigation, a useful technique for assigning the stereochemistry of E and Z-trimethylsilyl (TMS) enol ethers was developed using ¹H NMR nuclear Overhauser effect difference spectroscopy (NOEDS) experiments. One advantage of this technique over the widely used ¹³C NMR method is that only one isomer is required to accurately assign the Eor Z. stereochemistry. [Formula Omitted] / Science, Faculty of / Chemistry, Department of / Graduate

The preparation of the β-keto lactones 1̲9̲ via intramolecular alcoholysis of hydroxy Meldrum's acid derivatives was examined. Good yields of the 6- and 14-membered compounds were obtained, but the method was completely unsuccessful for medium-size rings. An investigation was conducted on the conformational preference of substituted 14-merabered lactones with a view to understanding the stereochemical consequences of the reactions of these compounds. The conformational preferences of simple 14-membered cyclic compounds were first determined. These preferences are described in terms of steric and electronic interactions, with the support of computer-calculated steric energies. A number of 14-membered lactones were prepared, beginning with the β-keto lactone 3-oxo-13-tetradecanolide (1̲3̲8̲). Hydride reduction of (1̲3̲8̲) gave the diastereomeric alcohols 1̲4̲6̲ and 1̲4̲7̲, which were then elaborated to give a series of derivatives. The stereochemistry and conformations of these compounds were determined by X-ray crystallography and/or nmr analysis. The preferred conformation was found to be Dale's [3434] diamond lattice model. The relative rates of reaction were determined for several reactions of the alcohols 1̲4̲6̲ and 1̲4̲7̲ and for one reaction of the corresponding acetates. The conformational effects were found to be much smaller than those observed in 6-merabered rings. Explanations of this difference are given. The preparation of the ⍺, β-unsaturated lactones 1̲6̲3̲ and 1̲6̲4̲, the β-methyl-⍺, β-unsaturated lactones 1̲8̲5̲ and 1̲8̲̲6̲̲, the dimethyl lactones 1̲5̲4̲ and 1̲5̲5̲ and the epoxides 1̲9̲7̲ and 1̲9̲8̲ are described. The resulting geometry of double bonds and the stereochemistry of substituents are explained in terms of conformational preferences. [Formula Omitted] / Science, Faculty of / Chemistry, Department of / Graduate

The conformationally controlled reactions of macrolides 42, 43, 72 and 74 were investigated. Treatment of these 14-membered lactones with hydride reducing agents and organocopper reagents led to diastereoselective product formation. The product distributions could be rationalized using low energy starting material or product conformations. A detailed conformational analysis involving MM2/MMP2 calculations and X-ray crystallographic studies led to a simple model for determining these low energy conformations. In order to simplify the identification of ring conformations, an improved procedure for the generation of polar maps was developed. With the aid of polar maps, a previously unknown low energy conformation for 14-membered rings was discovered. The discovery of this new conformation led to an improved nomenclature system for large rings, which considers the number of bonds separating both corner and pseudo corner atoms. Under this proposed nomenclature, the newly discovered conformation is designated the [34'3'4'] conformation. The work described in this thesis also led to a useful method for assigning the stereochemistry of trimethylsilyl enol ethers. Nuclear Overhauser effect difference spectroscopy (NOEDS) was used to unambiguously distinguish between E and Z trimethylsilyl enol ethers. One advantage of this technique over the widely used ¹³C NMR method is that only one isomer is required to accurately assign the E or Z geometry. [Formula Omitted] / Science, Faculty of / Chemistry, Department of / Graduate

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