Kinetic model of asymmetric dehydration of aldoxime catalyzed by immobilized OxdPsp in an organic solvent

Abstract

Aldoxime dehydratases (Oxds) have received considerable attention recently due to their application in the asymmetric synthesis of nitriles without cyanide by catalyzing the dehydration of aldoxime. However, the low stability of Oxds remains a huge obstacle to achieving high conversions and productivities of hydrophobic substrates. OxdPsp was immobilized on a macroporous adsorption resin (IOP) via an ATPS coupled with in situ immobilization. IOP-catalyzed dehydration of 2-phenylpropanal oxime (1) to prepare (S)-2-phenylpropanenitrile ((S)-2) was successfully performed with 95.7% yield, 94.1% ee and 98.6% conversion. The enriched (S)-nitrile (ee 94.1%) was obtained by using (E)-enriched aldoximes (E/Z = 97/3) as the substrate, which is consistent with the Gröger enantiopreference rule. A kinetic model to predict the dehydration catalyzed by IOP was established with an average deviation of 7.6%. The IOP-catalyzed dehydration reaction follows a sequential mechanism including substrate and product inhibition. Developing a kinetic model is a key step in the application of artificial intelligence in chemical engineering. After three recycling steps of IOP, the yield of (S)-2 still reached 83.6%, indicating that the stability of IOP was greatly enhanced, which was attributed to employing an organic solvent with a higher lg P value as the working medium and the immobilization protocol.