Development of Peptides for Enantioselective Hypervalent Iodine(III)-Mediated Chemistry and Functional Materials for Environmental Remediation

Within the field of asymmetric catalysis, many researchers have been inspired by the multifaceted structures and corresponding catalytic activity and selectivity of enzymes. One approach to mimicking the important characteristics of enzymes is to develop peptide-based catalysts for asymmetric transformations. Peptides containing even a small number of amino acids are able to provide an environment, rich with chiral information, that is adequate for the transfer of chirality. The overall goal of the presented research is to combine peptide-mediated asymmetric catalysis with hypervalent iodine (HI) chemistry in order to develop new and highly modular peptide catalysts for a variety of HI-mediated enantioselective transformations. HI compounds are recognized as valuable and attractive reagents due to their mild reactivity, high selectivity, and commercial availability as oxidants and electrophiles, while also reducing the overall negative environmental impact of these transformations. In particular, the emergence of catalytic and enantioselective processes with iodine(III) species is starting to make these compounds competitive with metal catalysts. Thus, one could imagine that the incorporation of an iodine(III) active site, such as an iodoarene moiety, into a peptide scaffold would result in asymmetric catalysts well suited for organic transformations such as the α-oxytosylation of propiophenone and oxylactonization of 5-oxo-5- phenylvaleric acid. While, these two reactions represent broadly studied catalytic iodine(III)-mediated transformations, they have yet to reach synthetically useful levels of enantioselectivty. The second part of this dissertation pivots to focus on the implementation of functional materials for environmental remediation techniques, such as, the capture of volatile organic compounds and pesticide degradation. Polyethylenimine (PEI) functionalized kaolinite clay was successfully prepared, characterized, and assessed for the remediation of volatile organic compounds (VOCs). A gas chromatographic vapor capture assay evaluated the capability of unmodified and modified clay material to capture representative aldehyde, carboxylic acid, and sulfur VOCs in a laboratory setting. Unmodified kaolinite clay was moderately effective at remediating these VOCs, while the amine functionalized kaolinite was exceptionally successful at selectively capturing organics in the vapor phase. Further, a series of amine-functionalized cellulose nanocrystal materials were successfully synthesized, characterized, and evaluated for the remediation of pesticide contaminants from organic and aqueous media. Their ability to degrade malathion in organic systems has been examined, resulting in up to 100% degradation of malathion into detectable lower molecular weight by-products. A poly(ethyleneimine)-grafted cellulose nanocrystal material was also effective at degrading malathion, deltamethrin, and permethrin in aqueous systems with 100%, 95%, and 50% reduction, respectively. Thus, these materials can potentially serve as a new and viable remediation technique based on their ability to effectively degrade various pesticides. The reusability of the amine-modified cellulose nanomaterial was also explored

Relative Rate Profiles of Functionalized Iodoarene Catalysts for Iodine(III) Oxidations

A series of rate studies were conducted to evaluate the steric and electronic properties that govern the reactivity of iodoarene amide catalysts in the α-oxytosylation of propiophenone. A meta-substituted benzamide catalyst emerged as the most reactive. This catalyst was employed in the α-oxytosylation of a series of substituted propiophenones, returning the α-tosyloxy ketone products in excellent isolated yield

Scaled Synthesis of Polyamine-Modified Cellulose Nanocrystals from Bulk Cotton and Their Use for Capturing Volatile Organic Compounds

We have previously demonstrated that cellulose nanocrystals modified with poly(ethylenimine) (PEI-f-CNC) are capable of capturing volatile organic compounds (VOCs) associated with malodors. In this manuscript, we describe our efforts to develop a scalable synthesis of these materials from bulk cotton. This work culminated in a reliable protocol for the synthesis of unmodified cellulose nanocrystals (CNCs) from bulk cotton on a 0.5 kg scale. Additionally, we developed a protocol for the modification of the CNCs by means of sequential 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) oxidation and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) coupling to modify their surface with poly(ethylenimine) on a 100 g scale. Subsequently, we evaluated the performance of the PEI-f-CNC materials that were prepared in a series of VOC capture experiments. First, we demonstrated their efficacy in capturing volatile fatty acids emitted at a rendering plant when formulated as packed-bed filter cartridges. Secondly, we evaluated the potential to use aqueous PEI-f-CNC suspensions as a spray-based delivery method for VOC remediation. In both cases, the PEI-f-CNC formulations reduced detectable malodor VOCs by greater than 90%. The facile scaled synthesis of these materials and their excellent performance at VOC remediation suggest that they may emerge as a useful strategy for the remediation of VOCs associated with odor

CCDC 1958147: Experimental Crystal Structure Determination

Related Article: Timothy R. Lex, Maria I. Swasy, Soham Panda, Beau R. Brummel, Lauren N. Giambalvo, Kristopher G. Gross, Colin D. McMillen, Khadijatul Kobra, William T. Pennington, Daniel C. Whitehead|2020|Tetrahedron Lett.|61|151723|doi:10.1016/j.tetlet.2020.15172