Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 158-168). Available also in a digital version from Dissertation Abstracts.

Examination of the scope of the [Rh(CO)₂Cl]₂-catalyzed allylic substitution reaction as well as the development of a domino [Rh(CO)₂Cl]₂-catalyzed allylic alkylation/Pauson Khand reaction is described. A number of experiments were carried out in order to explore the novel regioselectivity in the [Rh(CO)₂Cl]₂-catalyzed allylic substitution reaction, and the [Rh(CO)₂Cl]₂-catalyzed allylic substitution reaction was found to give products resulting from attack of the nucleophile on the carbon bearing the leaving group in a highly regioselective fashion in most cases. Examination of allylic carbonate substrates containing similar substitution at each allylic site was carried out, and conditions that minimize equilibration of active intermediates were determined. Intramolecular [Rh(CO)₂Cl]₂-catalyzed allylic alkylation was accomplished to synthesize challenging eight-membered lactone ring systems. Nucleophile scope was explored with regards to the [Rh(CO)₂Cl]₂-catalyzed allylic substitution reaction, and malonates, substituted malonates, aliphatic amines, and ortho-substituted phenols were all determined to be effective in the reaction. A domino [Rh(CO)₂Cl]₂-catalyzed allylic alkylation/Pauson-Khand reaction was developed which allows the rapid synthesis of bicyclopentenone products from simple, readily available starting materials. The first application of the Pauson-Khand reaction to the synthesis of azabridged bicyclic structures is also described. Various cis-2,6-disubstituted piperidines were cyclized to the corresponding azabridged bicyclopentenones is high yields often in high diastereoselectivities. The effect of ring size, nitrogen substituent, and remote functionality on the Pauson-Khand substrates was studied. The methodology developed was applied to the concise, enantioselective total synthesis of the antimalarial and anticancer indole alkaloid (-)-alstonerine. Pauson-Khand reaction of a readily available enyne synthesized in four steps from L-tryptophan provided a cyclopentenone in high yield as one diastereomer. Elaboration of the Pauson-Khand product required the development of a one pot conversion of a five-membered cyclic silyl enol ether to a sixmembered lactone and the mild acylation of a glycal.

DNA repair in Gossypium barbadense L. cotyledonary tissue was examined in vivo during early germination. DNA strand breaks were initiated by applying ethyl methanesulfonate (EMS) during seed imbibition. Strand rejoining was monitored through a period of EMS induced DNS synthesis by means of velocity sedimentation analysis. There was an absence of DNA molecular weight increase as disclosed by the sedimentation profiles. It is presumed velocity sedimentation evaluation was insensitive for detecting in vivo restoration of cotyledonous DNA strand breaks. The altered DNA synthesis response perceived within treated seedling cotyledons perhaps reflects, but does not establish the operation of a cellular mutagenic repair system. EMS induced morphological mutant cotton plants arising during the course of this investigation were cytologically identified as possessing duplicate-deficient chromosomes.

Synthetic efforts toward fumonisin analog were described. These are accomplished via amino acid Schiff base methodology. These efforts can be divided three major phases. First, tandem reductive alkylation with DIBAL/TRIBAL and different types of organo-lithium or Grignard nucleophiles provided threo-amino alcohol with excellent stereoselecitivites (2-27:1). The reductive alkylation utilized most hydrocarbon nucleophiles, e.g. alkyl-, vinyl-, alkenyl-, phenyl-, and dienyl-, and afforded high selectivites unless donor solvents (e.g. THF and Et2O) were used. Second, syntheses of the protected threo-γ-amino-β-hydroxy aldehydes and their stereoselectivities were introduced. The reductive alkylated threo-amino allyl alcohol was transformed via Brown’s hydroboration/oxidation protocol with 9-BBN, followed by TEMPO oxidation to give the resultant aldehydes in reasonable yields. Then, TBDPS and Schiff base protected aldehyde was coupled with phenyl- and decyl Grignard reagents to obtain predominant 3,5-anti-diols (ca. 80:20 anti:syn), characterized by ¹³C NMR analysis of Rychnovsky’s 1,3-acetonide groups. Products can be useful analogues for fumonisin and 5-hydroxy-sphingosine due to their structural similarity. Third stage involved the synthesis of C₁₁-C₂₀ fragment analog of fumonisin. Chiral auxiliaries (e.g. Evans and Myers) were administrated for stereoselective methylation, Sharpless asymmetric dihydroxylation in the presence of (DHQ)2PHAL catalyst was performed to form 1,2- syn-diols, and the manipulation of protection/deprotection and Finklestein reaction furnished C₁₁-C₂₀ fragment analog of fumonisin.

Stress conditions such as heat shock, UV, alkylating agents, and H2O2 have been shown to result in the modification of a variety of protein targets via the production of reactive electrophiles. These modifications can directly impact protein function or can alter posttranslational modifications, thus leading to a disruption of cellular regulatory processes. Recent studies have shown that stress-induced protein modifications can modulate posttranslational modification by the small ubiquitin related modifier (SUMO) family of proteins. Unlike ubiquitination, which primarily targets proteins for proteasomal degradation, sumoylation exerts a variety of effects including protein stabilization, subcellular localization, and the alteration of protein-protein interactions and transcriptional activity. To investigate the effects of alkylation and oxidative stress on sumoylation, HEK293 cells were treated with iodoacetamide, hydroquinone, benzoquinone, Texas Red C5 bromoacetamide, hydrogen peroxide, and 4-hydroxynonenal (HNE), a highly reactive product of lipid peroxidation associated with oxidative stress. Western blot analysis revealed that the agents tested resulted in concentration-dependent changes in the patterns of SUMO-1 and SUMO-2/3 protein conjugation. Localization studies using western blot analysis and confocal immunofluorescence microscopy demonstrated that SUMO-1 protein conjugates were located primarily in the nucleus, whereas SUMO-2/3 protein conjugates were more equally distributed between the nucleus and the cytoplasm. SUMO-associated proteins were harvested from vehicle- and HNE-treated non-transfected HEK293 cells using agarose conjugated anti-SUMO-1 antibodies or from HA-SUMO-1- and HA-SUMO-3-expressing HEK293 cells using immunoaffinity chromatography. Multidimensional liquid chromatography-tandem mass spectrometry analyses resulted in the identification of 54 HA-SUMO-1-associated proteins and 37 HA-SUMO-3-associated proteins in vehicle-treated cells and 21 HA-SUMO-1- and HA-SUMO-3-associated proteins in HNE treated cells. Additionally, 27 SUMO-1-associated proteins were identified in the HNE-treated non-transfected cells. The functional classes of proteins targeted included RNA binding and processing proteins, metabolic enzymes, cytoskeletal regulators, and chaperone proteins. HNE treatment resulted in a near complete redistribution of both SUMO-1 and SUMO-3 to different targets. There was a 15% overlap in SUMO-1 and SUMO-3 associated proteins in vehicle-treated cells and a 10% overlap in HNE-treated cells indicating that SUMO proteins target distinct protein groups. These results indicate that protein modifying reactive electrophiles can regulate protein functions through the indirect alteration of endogenous posttranslational modifications.

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The Knoevenagel reaction is defined by the condensation of an aldehyde or ketone with a carbon nucleophile produced by the deprotonation of a methylene species whose acidity is dramatically increased by bonds to strongly electron withdrawing groups. Previously, our group developed an effective one-pot method for the preparation of 4H-chromenes using sodium borohydride reduction of the cyclized intermediates formed by the Knoevenagel condensation of malononitrile with salicylaldehydes in aqueous ethanol. In this study we outline the extension of these strategies to include 2’-hydoxyphenylketones as the starting material. Many of these compounds are also unique and were prepared by Friedel-Crafts acylation of phenols with acyl chlorides and/or Fries Rearrangement of the corresponding phenyl ester. The objective of this project has been to expand the application of the methods optimized in our lab for the simple and efficient formation of carbon-carbon bonds via the selective reduction of the alkylidene portion of the Knoevenagel reaction products. These methods have allowed for the production of several important classes of natural product-like compounds. Specifically, in this investigation, we have adapted these methods to the production of various 4-alkyl and 4-aryl substituted 3-amino-2-cyano-4H-chromenes. These types of molecules exhibit diverse pharmacological activity and have been shown to be potentially useful for the treatment of various diseases. A subset of the synthesized compounds will be submitted to Eli Lilly through their PD2 program. Further variation of substrates included the reaction of salicylaldehydes with ethyl cyanoacetate or cyanoacetamide which provided products unreported in the literature. Reactions with cyanoacetates gave the expected 3-carboethoxy(ester) functionalized 4H-chromene compounds. Products from cyanoacetamide were found to occur in open rather than cyclized forms. / Introduction and background literature -- Synthesis of 2'-hydroxyphenylketones -- Synthesis of 2-amino-3-cyano-4H-chromenes -- One pot method applied to salicylaldehydes with ethylcyanoacetate or cyanoacetamide. / Department of Chemistry

A powerful new one-pot method has been developed for the reductive alkylation of malononitrile with aromatic aldehydes. This new procedure has vastly improved the yield and efficiency and increased the scope for the aromatic aldehydes. Incorporating water as the catalyst in ethanol for the condensation step allows stoichiometric amounts of malononitrile and aldehyde to be employed. After dilution and cooling the reduction step takes place quickly and efficiently with sodium borohydride to give monosubstituted malononitriles.The product from the reductive alkylation of malononitrile with 2-quinolinecarboxaldehyde quickly rearranges to a novel indolizine on silica gel or with heat, while alkylation of the monosubstituted derivative provides an unsymmetrically disubstituted malononitrile.We have also investigated this improved one-pot reductive alkylation using various 2-hydroxybenzaldehydes where intramolecular cyclization occurs following the condensation step and various 2-amino-3-cyano-4H-chromenes are formed. / Department of Chemistry