Engineering a norcoclaurine synthase for one-step synthesis of (S)-1-aryl-tetrahydroisoquinolines

Abstract

Tetrahydroisoquinoline alkaloids (THIQAs) are ubiquitous compounds with important pharmaceutical and biological activity. Their key N-heterocyclic structural motifs are synthesised via Pictet–Spengler (P–S) reaction by norcoclaurine synthases (NCS) in plants. The synthesis of 1-aryl-tetrahydroisoquinoline alkaloids has attracted increasing attention due to their antitumor and antivirus activities. Herein, the L68T/M97V mutant of NCS from Thalictrum flavum with improved activity was developed by semi-rational design. This mutant not only showed higher catalytic performance (> 96% conversion) toward benzaldehyde and dopamine over the wild-type enzyme, but also catalysed the P–S reaction of the bulky substrate 4-biphenylaldehyde and dopamine with high conversion (> 99%) for the effective synthesis of 1-aryl-THIQA. In terms of stereoselectivity, all products synthesised by the L68T/M97V mutant showed high optical purity (92–99% enantiomeric excess). Graphical Abstract

Computational mechanistic investigation of the kinetic resolution of α-methyl-phenylacetaldehyde by norcoclaurine synthase

“…The kinetic data is not available for the considered reaction here but accessible for the reactions of structurally similar aldehyde substrates 30 . The measured k cat values for two other non-natural substrates, benzaldehyde and 4-biphenylaldehyde, are 0.237 s −1 and 0.001 s −1 , respectively, which can be converted to barriers of ~19 kcal mol −1 and 23 kcal mol −1 .…”