April 2020-2: Another study with ω-transaminases in neat organic solvents
Following our previous work on the use of ω-transaminases that were immobilised on functionalised controlled-porosity glass beads and operated in organic solvents (see March 2020), we investigated the applicability of the immobilised biocatalyst in a parallel interconnected kinetic asymmetric transformation (PIKAT). PIKAT is a cascade in which one or two enzymes use the same cofactor to convert two reagents into more useful products. In this work, we describe a PIKAT catalysed by an immobilized ω-transaminase (ωTA) in neat toluene at controlled water activity. In practice, the process concurrently combines an asymmetric transamination of a ketone into an α-chiral amine with an anti-parallel kinetic resolution of an amine racemate. The applicability of the PIKAT was tested on a set of prochiral ketones and racemic α-chiral amines in a 1:2 molar ratio, which yielded elevated conversions (up to >99%) and enantiomeric excess (ee, up to >99%) for the desired products. The progress of the conversion and ee was also monitored in a selected case. This is the first report of a PIKAT using an immobilized ωTA in a non-aqueous environment.