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<p> Chemical identity is a foundational crosscutting concept in chemistry and encompasses the knowledge, reasoning, and practices relevant for the classification and differentiation of substances. Substances are found everywhere &ndash; from the chemistry classroom to the kitchen at home &ndash; so classification and differentiation of substances is important for everyday decisions as well as challenges that are solved using chemistry. An understanding of chemical identity, then, is essential for scientifically literate citizens in addition to students training to be chemists. A better understanding of how chemical identity thinking develops could be used to inform instruction and education research, with the intent of producing students and citizens who can use their chemical knowledge to reason with in order to practice chemical identity thinking. </p><p> This thesis characterizes chemical identity thinking from the perspective of chemical identity knowledge and chemical identity practices, both of which contribute to chemical identity thinking. First, the literature is examined for existing research on how students perceive substances and chemical identity, and a hypothetical learning progression for chemical identity thinking is proposed. This is followed by the design of a qualitative instrument, the CSI Survey, to capture the chemical identity practices exhibited by students at a range of education levels (8th grade &ndash; 4th year university). The data collected using the CSI Survey are analyzed using content analysis. Eight unique themes corresponding to chemical identity practices (the application of chemical identity knowledge and reasoning) are revealed by this analysis (<i>change, class, composition and structure, function, organism effect, sensory information, source, tests and experimental values</i>). The application of chemical identity knowledge in biochemical contexts by both expert biochemists and biochemistry students is investigated in the final chapter, and the chemical identity knowledge observed in the biochemical contexts is characterized using the eight themes of chemical identity practices. Suggestions are offered on how the products of the research on chemical identity thinking can be used to inform decisions in both instruction and research.</p>

Aeruginosins are a family of marine natural products containing mostly non-proteogenic amino acids. These compounds contain a common 2-carboxy-6-hydroxy-octaindole (Choi) rigid bicyclic structure. Many aeruginosins are inhibitors for enzymes involved in the blood coagulation cascade, such as thrombin and Factor VIIa. In order to understand the structure activity relationship (SAR) of the aeruginosins and to discover novel anticoagulants with potentially improved inhibitory and pharmacokinetic properties, in the first part of my thesis I have discussed, synthesis of a series of novel analogs of aeruginosin 298-A, in which the Choi will be replaced with L-proline and oxygenated Choi analogs, and the Argol is replaced with various other functionalities. The preparation of oxygenated Choi analogs starting from glucose using a new method has been discussed. In the second part of my dissertation, I have discussed the design, synthesis and self–assembly of glucosamine based hydro and organogelators. Carbohydrate-based low molecular weight gelators are an interesting class of molecules with many potential applications. A series of amides and ureas were prepared from the protected D-glucosamine from the corresponding acid chloride and isocyanates. The self-assembling properties of these compounds were studied in several solvents, including water and aqueous solutions. Most of these compounds were found to be efficient low molecular weight hydrogelators (LMHGs) for aqueous solutions. The preparation and characterization of these compounds will be elaborated.

Ortho-quinone methides are reactive intermediates with wide ranging applications in organic synthesis. However, their propensity to rearomatize renders them transitory and reactive, which has made their implementation in organic synthesis challenging. An asymmetric and organocatalytic multicomponent reaction platform was developed to address this challenge by accessing ortho-quinone methide intermediates in situ through a Friedel-Crafts hydroxy-alkylation condensation of phenols, aldehydes, and boronates. This approach provided a practical and general method to access to chiral di- and triaryl methane products in high yields and enantioselectivities from commercially available starting materials. An unanticipated cyclization pathway was discovered while exploring the scope of the reaction that afforded 2,4-diarylchroman products from an electron rich styrenyl boronate. Reaction conditions were optimized to select for the cyclization pathway, which afforded chroman products with high levels of enantio- and diastereoselectivity. The myristinin natural products are DNA polymerase-β inhibitors and DNA-damaging agents that contain a privileged chroman scaffold within their core. The multicomponent cyclization strategy was applied towards the synthesis of the myristinin natural products without success. To circumvent issues with reactivity, the multicomponent reaction platform was extended to an intermolecular cycloaddition of in situ generated ortho-quinone methides from phenols, aldehydes, and styrenes to provide 2,4-diarylchromans. The core of myristinins B/C was synthesized using the multicomponent cycloaddition strategy providing high yield and diastereoselectivity with remarkable step economy. An enantioselective version of the multicomponent cycloaddition reaction was developed utilizing triisopropyl borate Lewis acid and a chiral biphenol. / 2018-06-21T00:00:00Z

Asymmetric nucleophilic boronate reactions have been developed using organic chiral diols, specifically binaphthols, as catalysts. A highly enantioselective allylboration of acyl cyanides under solvent-free conditions was catalyzed by (S)-Br2BINOL. The reaction proceeds through single exchange of boronate with the chiral catalyst, promoted by tert-butanol. Allylation products were obtained in yields up to 97% and enantioselectivities up to 99:1 er. Syn- and anti-crotylborations of benzoyl cyanide were also performed, and the corresponding a-methyl products were isolated in good yields and moderate to good enantioselectivities, with the E-boronate producing a single diastereomer. This methodology represents a new route to enantioenriched homoallylic cyanohydrins through nucleophilic addition of the allyl group to acyl cyanides. The enantioselective Petasis reaction of glycolaldehyde dimer to synthesize b- amino alcohols was also investigated. With commercially available aldehyde dimer, boronic acids, and amines, electron-rich a-arylglycinols were obtained in up to 92% yield and up to 99.5:0.5 er. Direct inject mass spectrometry studies revealed a single exchange between p-methoxyphenylboronic acid and (S)-Br2BINOL, as well as coordination of the imine intermediate to the catalyst-boronate complex. This reaction was further optimized to include electron-deficient boronic acids. Addition of Lewis acidic triethylborate had a two-fold effect on the reactivity; it facilitated both the exchange of boronic acid with catalyst, and the formation of the imine intermediate. Using chloroform as the solvent, and (S)-Ph2BINOL, halogenated phenylboronic acids participated well in the Petasis reaction. This methodology is the first asymmetric Petasis reaction of glycolaldehyde to produce b-amino alcohols. / 2018-12-06T00:00:00Z

Disclosed herein are comprehensive details of a study on the total chemical synthesis of daphnane diterpene orthoesters (DDOs), a large group of secondary metabolites isolated from the plant families Eurphorbiacaea and Thymelaeaceae which are known to possess a broad spectrum of powerful biological activities. Characterized by a tricyclo[9.3.0.0]tetradecane core ring system with two trans-fused ring junctures, an average of nine oxygen appendages, and an unusual orthoester functionality, DDOs are amongst the most complex and structurally varied diterpene natural products and present a significant challenge towards de novo chemical synthesis. These studies culminated in short (10-12 steps from known starting materials, 16-18 total operations), stereocontrolled syntheses of tricyclic DDO cores containing seven contiguous stereocenters, of which six directly correspond to all known DDOs. Key to their assembly was the development of a concise p-quinol functionalization choreography that enabled rapid access to C-ring stereopolyads from simple precursors. Efforts to apply this strategy to the total synthesis of (±)-resiniferatoxin (RTX) are described in addition to a discussion for future work from this laboratory. / 2019-11-27T00:00:00Z

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No description available.

No description available.