Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

This doctoral dissertation described herein will be comprised of two parts. The first portion will address our efforts towards the synthesis of [alpha]-amino carbonyls from silyl enol ethers and the second portion will describe our unrelated efforts towards the synthesis of proaporphine alkaloids. A full discussion of the relevant literature, experiments and development of the methodologies will be provided along with all relevant experimental data. Part I: The [alpha]-amino carbonyl moiety has great potential for being a very useful synthetic intermediate for the incorporation of nitrogen owing to the synthetic utility and versatility of the carbonyl functional group. Despite this potential the synthesis has long been problematic owing to their tendency to undergo condensation reactions. We aimed to synthesize them utilizing a protected carbonyl in the form of a triisopropylsilyl enol ether and an electrophilic nitrogen source that could incorporate the nitrogen via an ene-[2,3] sigmatropic reaction sequence. To this end we used an N-sulfinyl carbamate as an electrophilic source of nitrogen that could be utilized for a regiospecific allylic amination of alkenes or could be used to form a highly reactive sulfur diimide that could be used for the allylic amination of alkenes or silyl enol ethers. Part II: Many pharmacologically important and synthetically interesting alkaloids have been formed in nature by the o,p oxidative phenolic coupling of various benzyl-tetrahydroisoquinoline alkaloids. One major class of alkaloids derived from this generalized oxidation is the proaporphine alkaloids and they possess an acid labile spirocyclic-dienone system obtained from this coupling. These compounds have great potential for being used for their anesthetic properties. Despite the relative ease of synthesizing the benzylisoquinoline alkaloids the application of the biomimetic oxidative coupling to make the quaternary center of these compounds gives very poor yields. We opted to form this spiro-dienone system by using a two step Suzuki coupling-para phenolate alkylation methodology that had been used to synthesize the related alkaloids codeine and narwedeine. In doing this we opted to extend the practical application of this methodology by the displacement of an alcohol derived leaving group. / text

(-) Codeine, (-) morphine, and their semi-synthetic derivatives play an integral role in medicinal analgesia. Due to a complex list of undesirable side effects, their effective use is often complicated and troublesome giving cause for the investigation of novel semi-synthetic analogs for efficacy and side-effect profile. It was envisioned that new and interesting codeine analogs could be synthesized via an opening of a hindered 7,8-[alpha]-epoxide. Classically, hindered epoxides are formed via halohydrin formation and subsequent closure. Interestingly, the 7,8-epoxide formed via bromohydrin closure was resistant to reaction with small nucleophiles, such as oxygen and hydride, but reactive towards large and nucleophilic atoms, such as sulfur and bromide. It was discovered that the epoxide was in fact the less hindered 7,8-[Beta] epoxide via x-ray analysis of various compounds. This hinted at an unexpected rearrangement which most likely occurred during the bromohydrin formation due to the severe steric interactions present in the core structure of codeine. Due to the reversibility of bromonium ion formation, a highly hindered double bond can produce the opposite configuration of what is expected when subjected to aqueous brominating conditions. Many popular alkaloids, including codeine and galanthamine, are biosynthetically formed via a spirocyclic dienone intermediate. In nature these intermediates are formed via an enzymatically driven phenolic oxidation; however in the lab this reaction has proven difficult to reproduce. In a previous Magnus publication, (±) codeine and (-) galanthamine, were synthesized via a common spirocyclic cross-conjugated dienone intermediate similar to the intermediate found in nature. Most importantly, this intermediate was formed without a phenolic oxidation. Instead, a para-alkylation of an appropriately substituted phenol efficiently created the key intermediate. Expanding on this phenolic alkylation strategy, various biaryl systems were built in order to investigate the scope and limitations of this reaction. Multiple para- alkylations proved successful while ortho- alkylations unveiled an interesting rearrangement which occurs during the reaction. Lastly, it was determined that a 7-membered ring could not be set using a phenolic alkylation strategy. / text

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

A reactive distillation column for the alkylation of benzene with long chain linear olefin was studied. The study involved design, construction, experimentation, and simulation of the column. Establishing the design required study of reaction rates, thermodynamic relationships, and packing structures. A heuristic was developed for the design of such columns. This heuristic involved estimating an amount of catalyst loading and subsequently determining the operating parameters for a column. This method is particularly applicable to systems with high concentrations of inert feeds. A column was constructed following the design. Data was collected from the column and compared to simulations. The simulations were performed with Aspen Plus RADFRAC. In this manner, the data was used to validate the commercial steady state models for reactive distillation. In addition, dynamic simulations of the system were performed. These dynamic simulations provided insight into more design considerations. For example, steady state simulations indicated an optimal feed stage based on steady state conversion of the olefin. However, the dynamic simulations showed a potential disadvantage to the utilization of the optimal feed stage. With some disturbances, a column configured with the feed stage with the highest steady state conversion also deviated from the steady state faster and with greater amplitude than other configurations. These considerations were further explored in developing a control scheme for reactive distillation columns. Control of reactive distillation differs from traditional distillation in that one control variable is conversion. Traditional distillation generally focuses on production rates and product purity. To this end, control schemes were analyzed and dynamic simulations were performed. These simulations showed an advantage to a variable pairing in which duty is paired with conversion. The conversion was inferred from a stage temperature in the reactive zone. In addition, distillate rate may be paired with product composition. In conclusion, the reactive distillation column design for long chain olefin alkylation of benzene requires careful estimation of catalyst requirements and valid simulation tools. In addition, dynamic response should be considered in the design. Finally, a simple inferential control scheme may be adequate. / text

Pseudoephedrine has been used as a chiral auxiliary in diastereoselective alkylation reactions, providing easy access to enantiomerically enriched carboxylic acids, alcohols, ketones, and aldehydes. Because pseudoephedrine can be transformed into methamphetamine and other illegal drugs, many countries restrict or ban its sale and distribution, which can complicate its use in academic and industrial settings. This thesis shows that (1S,2S)-2-methylamino-1,2-diphenylethanol and (1R,2R)-2-methylamino-1,2- diphenylethanol (synonymously, (1S,2S)- and (1R,2R)-pseudoephenamine 30, respectively) enable a broad range of utilities in asymmetric synthesis that meet or exceed those that previously characterized the pseudoephedrine system alone, with several advantages. First, these auxiliaries are free from regulatory restrictions and are not known to be transformable into illegal substances; second, asymmetric alkylation reactions that employ pseudoephenamine as a chiral auxiliary proceed with equal or greater diastereoselectivities than the corresponding reactions employing pseudoephedrine, with notable improvements in the selectivities of the alkylation reactions that form quaternary carbon stereocenters; and lastly, amides derived from pseudoephenamine exhibit a greater propensity to be crystalline compounds than the corresponding pseudoephedrine derivatives. / Chemistry and Chemical Biology

Pseudoephedrine is well established as a chiral auxiliary in the alkylation of amide enolates to form tertiary and quaternary carbon stereocenters. However, due to its facile transformation into the illegal narcotic methamphetamine, pseudoephedrine is either illegal or highly regulated in many countries, which limits its use in academic and industrial settings. To address this issue, pseudoephenamine has been developed as a replacement for pseudoephedrine in organic synthesis. This new auxiliary suffers no regulatory issues and exhibits several practical advantages over pseudoephedrine, including the high diastereoselectivities observed in alkylation reactions forming quaternary carbon stereocenters, the propensity for pseudoephenamine amides to be free-flowing crystalline solids, and the sharp, well-defined peaks that typically compose the 1H NMR spectra of these amides. / Chemistry and Chemical Biology

No description available.

With the increasing realization of their involvement in numerous biological processes, synthetic oligosaccharides present promising potential in drug and vaccine discovery. Selective functionalization of hydroxy groups in polyols represent a long-standing goal in chemistry since the chemical synthesis of O-glycosides often requires extensive protecting group manipulation. Organoboron catalysis is a recent strategy for regioselective activation of the equatorial hydroxy group of cis-vicinal diols. Following the initial findings that diarylborinic acid catalyzes the regioselective acylation of carbohydrate derivatives, kinetic studies were conducted to obtain better insight on the mechanism. Thereafter, the ability of diarylborinic acid to catalyze the regioselective alkylation of carbohydrates was demonstrated. Finally, investigations in the capability of diarylborinic acid to influence regiochemical outcome of glycosylation reactions were explored. Similarly, kinetic experiments were devised to shed light on the mechanism of the reaction.