Benign Tunable Solvents for Improved Processing of Pharmaceutically Relevant Products and Catalysts
Hill, Elizabeth M.
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Sustainable technologies are vital to reducing the environmental impact of chemical enterprises. Solvents are often seen as just a medium in which a reaction takes place; however they can also play a dominant role in the overall toxicity of a typical pharmaceutical/fine chemicals batch chemical operation. Further, careful solvent selection for a reaction may also lead to more facile separation and purification of products, thus reducing the overall cost of a chemical process. This thesis presents an environmentally benign processing technique for sustainable biocatalytic reactions coupled with facile built-in separation. An organic aqueous tunable solvent (OATS) system allows access to a hydrophobic substrate which is transformed with a homogeneous enzymatic catalyst in a single liquid phase. Subsequent CO2 addition produces a biphasic mixture where the hydrophobic product partitions preferentially into the organic rich phase for separation while the hydrophilic enzyme catalyst partitions into the aqueous rich phase, where it is recyclable. Processing parameters in OATS systems are discussed and an overall product recovery of 80% is observed after six reaction cycles. Additionally, greater than 99% enantiomeric excess (ee) is shown for catalyzed hydrolysis of rac-1-phenylethyl acetate with Candida antarctica lipase B (CAL B) both before and after CO2-induced separation.