Asymmetric Synthesis of the Oxidative Metabolites of Di(2-ethylhexyl) Phthalate and Analysis of Binding with Peroxisome Proliferator-Activated Receptors
Date of Award
Bachelor of Science
Chemistry and Physics
Department Chair or Program Director
Major or Concentration
Di(2-ethylhexyl) phthalate (DEHP) is a widely used plasticizer that is known to be an endocrine disrupting chemical (EDC). Exposure to its primary metabolite, mono(2-ethylhexyl) phthalate (MEHP) and other secondary oxidative metabolites is associated with adverse health effects in vivo which are linked to interactions with nuclear hormone receptors such as peroxisome-proliferator activated receptors (PPARs). Although these molecules are chiral, differences in the toxicity of each stereoisomer are not well studied. By synthesizing the enantiomers of these molecules and testing their affinity for PPARγ by thermal shift assay (TSA), potential differences in binding affinity of each form can be determined. Enzymatic resolution of racemic 2-ethyl-1-hexanol by a combination of non-immobilized and immobilized Amano Lipase species gave enantiomerically pure primary alcohols. These alcohols were esterified with phthalic anhydride, yielding (R)-MEHP (68% yield), (S)-MEHP (68% yield), (R,R)-DEHP (34% yield), (R,S)-DEHP (13 % yield), and (S,S)-DEHP (94 % yield). Thereafter, racemic synthesis of three secondary oxidative metabolites, mono-[2-(carboxymethyl)hexyl]phthalate (2cx-MMHP), mono-(2-ethyl-5-carboxypentyl)phthalate (5cx-MEPP), and mono-(2-ethyl-5-oxohexyl)phthalate (5oxo-MEHP), was completed in four steps with yields of 11%, 5.7%, and 11%, respectively. Preliminary TSA results show the need for further optimization of protein:dye ratios and evaluation of the PPARγ solution used for unwanted binding with pre-existing ligands. Ultimately, completed asymmetric synthesis of the secondary oxidative metabolites and evaluation of all products by TSA, or other measure of protein-ligand stability, will serve as a means for determining if a chiral component to phthalate toxicity is present within DEHP metabolism.
Harris, Hannah, "Asymmetric Synthesis of the Oxidative Metabolites of Di(2-ethylhexyl) Phthalate and Analysis of Binding with Peroxisome Proliferator-Activated Receptors" (2023). Student Research Submissions. 531.