Synthesis of (1R,3R)-1-amino-3-methylcyclohexane by an enzyme cascade reaction

Amine transaminases (ATAs) are powerful enzymes for the synthesis of chiral amines. Although the request for amines with more than one chiral center is increasing, their synthesis is still challenging. Here we show a casacde reaction combining an enoate reductase (ERED) and an amine transaminase (ATA-VibFlu), which allows access to optically pure (1R,3R)-1-amino-3-methylcyclohexane. Because all known wildtype EREDs show a (S)-selectivity for 3-methylcyclohex-2-enone and the ATA-VibFlu only showed a modest enantioselectivity, different variants of EREDs and ATAs were investigated and suitable mutant enzymes were identified. In whole cell biocatalyses using the ERED YqjM Cys26Asp/Ile69Thr and the ATA-VibFlu Leu56Ile (1R,3R)-1-amino-3-methylcyclohexane was obtained at high optical purity (97% de).