Secondary Screen and E Determination

A more thorough analysis of the enantioselectivity of several commercially available alkaline proteases was performed by determining the enantioselectivity fador E of these enzymes in the hydrolysis of (R,S)-4. In order to determine the enantioselectivity factor E accurately (the kinetic ratios for the conversion of the two enantiomers in a first-order kinetic resolution) [11], accurate measurement of the optical purity of the product acid and unreacted ester is necessary. Separation of the carboxylic acid enantiomers by gas chromatography was not possible due to decomposition of the acid on the column, so a derivatization method was developed to convert the acid into the corresponding methyl ester. Treatment of the extracted acid and ester with trimethylsilyldiazomethane resulted in the conversion of the acid into the methyl 

Entry Enzyme Configuration/% ee of remaining ester Relative conversion 

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