Open Access

The aim of our research is a stereoselective synthesis development of 4-aminocyclohexanol by the application of a keto reductase (KRED) and an amine transaminase (ATA). 4-Aminocyclohexanol is a valuable precursor for active pharmaceutical ingredients, for example, lomibuvir (a HCV protease inhibitor), ambroxol (a secretolytic agent) and other bioactive molecules. Today, the trans-4-aminocyclohexanol is accessed via Ni-catalyzed synthetic procedure giving moderate yields. In our project we perform cis- and trans-4-aminocyclohexanol synthesis from 1,4-cyclohexanedione (a bio-based precursor) by an one-pot approach combining sequentially a KRED and an ATA as catalysts. For this, we envisaged two multistep enzymatic procedures. The route A would involve 4-hydroxycyclohexanone formation from 1,4-cyclohexanedione via a KRED-catalyzed monoreduction and a further transamination mediated by an ATA towards 4-aminocyclohexanol. The route B would consist of switching the steps of the previous sequential approach, that is, a monoamination of the diketone to yield 4-aminocyclohexanone, and the subsequent reduction of the remaining carbonyl group. Only route A turned out to be feasible, and we performed 4-aminocyclohexanol synthesis at the preparative scale in the sequential and tandem modes. Depending on the ATA, both isomers can be obtained.