Fluorogenic Cyanohydrin Esters as Chiral Probes for Esterase and Lipase Activity

Abstract

Abstract Fluorogenic cyanohydrin esters were prepared that release the fluorescent product umbelliferone by secondary decomposition of the primary cyanohydrin reaction product by cyanide elimination to the aldehyde and subsequent β‐elimination. Whereas butyrate 1b and octanoate 1d show the highest reaction rates with enzymes, the highest relative rates above the non‐catalyzed background reaction are achieved with pivalate 1c and benzoate 1e . Enantioselective reactions are detected when the conversion stabilizes at 50% of the maximum fluorescence release, and enantioselectivity is confirmed by chiral‐phase HPLC analysis of the unreacted cyanohydrin ester substrate.