Enzymatic Cascade in a Simultaneous, One-Pot Approach with In Situ Product Separation for the Asymmetric Production of (4S,5S)‑Octanediol

Stereopure aliphatic diols are an interesting class of compounds because of their potential applications as precursors for chemical catalysts, for high-value polymers, or as precursors for cyclic acetals. We present a simultaneous enzymatic two-step, one-pot cascade for the synthesis of vicinal diols with excellent de and ee values with the exemplary reaction system from butanal to (4S,5S)-octanediol. This reaction is restricted by an unfavorable reaction equilibrium. For an intensification of the reaction toward higher conversions in equilibrium and increased space time yields (STY), aqueous, microaqueous, and biphasic reaction systems for in situ product removal (ISPR) were experimentally investigated and compared. Process concepts for the purification of (4S,5S)-octanediol from each reaction system were developed and assessed in terms of product-specific energy demand. The two-phase reaction system for in situ product removal is favorable for the enzymatic reactions in terms of yield and STY at different time points. In comparison to the aqueous and microaqueous reaction systems, the specific energy demand for (4S,5S)-octanediol recovery is drastically reduced by approximately a factor of seven when performing ISPR using a biphasic system in comparison to an aqueous reaction system.