Description of Research with Mark Pugh
(In conjunction with Kerensa Sorensen-Stowell and Susan Ward)
I was formally trained to be a physical organic chemist, which means that I am trained to study stability, bond energy, enthalpies, entropies, etc. for organic molecules in relation to their modes or mechanism of action. The research I will be doing will be in conjunction with Sister Kerensa Sorensen-Stowell and Sister Susan Ward. Each semester one of us will be the principle investigator in charge of directing the organic research group. I will likely accommodate 1-9 students the semester that I am the principle investigator on this combined research effort with Kerensa Sorensen-Stowell and Susan Ward. If you are interested in doing research with me or with Sister Sorensen-Stowell or Sister Ward, come and talk to one of us.
Project #1: Isolation of a Furanocoumarin: Xanthotoxin from the Umbelliferae plant (aka Bishop's Flower). This research project was started by Dr. Pugh in an effort to isolate xanthotoxin from its natural source, Bishop's Flower. The molecule was used by ancient Egyptians to treat Leukoderma and other skin rashes. The individual that was to use this drug bathed in a bath of ground up Bishop's Flower. They would then lie out in the sun to treat their skin ailments. Today, xanthotoxin is widely used to treat T-cell lymphoma via extracorporeal photopheresis. The goal of the research project this fall is to increase isolated yields of xanthotoxin. We are also attempting to look at hydrogen-bond interactions between purified xanthotoxin and nucleotide bases in solution.
Project #2: Formation of Imine Derivatives. The key step in vision is the binding of retinol (vitamin A) to the enzyme opsin via a primary amine to form rhodopsin, an imine. When rhodopsin absorbs a photon of visible light, a cis double bond undergoes photochemical isomerization to trans. This change results in a nerve impulse that the brain interprets as a visual image. In an effort to mimic this process, we are using benzaldehyde and trans-cinnamaldehyde as our aldehyde source. We are then binding different primary amines, some alkyl and others aryl, to the aldehyde via an imine bond. The amines we are studying are aniline, cyclohexylamine, o-diaminobenzene, m-diaminobenzene, and p-diaminobenzene. We obtain colored products that are similar to rhodopsin. We analyze these products via melting point, infrared spectroscopy, 1H NMR, 13C NMR, GC-MS, and UV-Vis spectroscopy.
Project #3: Study of Stereoselective and Regioselective Reactions of Alkenes. This project focuses on designing molecules that demonstrate Markovnikov and Anti-Markovnikov additions to alkenes. To date, the alkenes that we are using are cyclohexene, 1-hexene, and 3-methyl-1-pentene. Due to the non-stereospecific nature of cyclohexene, it is a good molecule to test the viability of addition reactions without worry as to the regiochemistry of addition to the alkene. We study 1-hexene to be able to see regioselectivity as additions to the alkene occur. We also study 3-methyl-1-pentene to be able to see regioselectivity and view potential hydride shifts as a result of additions to the alkene. Currently, we are investigating the formation of halohydrin products from the addition of NBS (N-bromosuccinimide) in water to these alkenes. Halohydrin reactions are both regioselective and stereoselective (anti addition along double bond). We are also investigating the formation of alcohols from the reaction of the alkenes with mercuric acetate in tetrahydrofuran followed by reduction with basic sodium borohydride. This reaction is known to be regiospecific (Markovnikov) and occurs without the formation of a carbocation intermediate as has been demonstrated by the use of 3-methyl-1-pentene. We have analyzed these products via melting point, infrared spectroscopy, 1H NMR, 13C NMR, and GC-MS. In future we hope to study Markovnikov additions of water to these alkenes that would demonstrate the formation of a carbocation intermediate. We also hope to investigate the Anti-Markovnikov addition of water to these alkenes.