Multi-Choice Enzymatic Resolutions of Racemic Secondary Alcohols Using Candida antarctica Lipase B. A Collaborative Experiment for Advanced Undergraduates

An advanced bioorganic chemistry laboratory set of experiments is described in which the lipase B from Candida antarctica is used for the kinetic resolution of four racemic secondary alcohols. The biotransformations are transesterification reactions of these alcohols, as well as hydrolyses and aminolyses of (±)-1-phenylethyl acetate. Independent work is assigned to each student, and the overall results are analyzed at the end of the laboratory course. Mosher’s method and the so-called modified Mosher’s method are used to determine the enantiomeric excesses and absolute configurations, respectively, of products and remaining substrates. In addition to learning several advanced laboratory techniques and making intensive use of NMR spectroscopy, the students become familiar with enzymatic methodologies and, especially, with the employment of enantioselectivity values for evaluating the stereochemical efficiency of the processes.