One‐pot sequential and cascade processes performed by employing ene‐reductases (ERs) together with ω‐transaminases (ω‐TAs) for the obtainment of diastereomerically enriched (R)‐ and (S)‐amine derivatives containing an additional stereocenter were investigated. By using either α‐ or β‐substituted unsaturated ketones as substrates and by coupling purified ERs belonging to the Old Yellow Enzyme (OYE) family with a panel of commercially available ω‐TAs, the desired products were obtained in up to >99 % conversion and >99 % de. The sequential reactions were performed in a one‐pot fashion with no need to adapt the reaction conditions to the reductive amination step or to purify the reaction intermediate. Moreover, high chemoselectivity of the tested ω‐TAs for the saturated ketones was shown in the cascade reactions.

A fast and sensitive colorimetric assay (FRED, fast and reliable ene-reductases detection) that allows the estimation of levels of conversion of ene-reductase (ER)-catalysed reactions has been developed. The activated olefin is reduced by ER at the expense of NAD(P)H cofactor, whose regeneration is carried out in situ by the glucose/glucose dehydrogenase system. Subsequently, the consumption of the co-substrate glucose is determined colorimetrically by a multienzymatic system. The FRED assay offers a wide range of possible applications, from enzyme fingerprinting and kinetic analysis, to primary screening of enzyme libraries and optimisation of ERs' performances under different reaction conditions.

The Cover shows the one‐pot coupling of ene‐reductases and ω‐transaminases to achieve the biocatalytic synthesis of diastereomerically enriched (R)‐ and (S)‐amines containing an additional stereocenter starting from either α‐ or β‐substituted unsaturated ketones as substrates. In their Communication, S. Riva and co‐workers demonstrate that the amine products can be obtained with excellent stereoselectivity and up to quantitative conversion in sequential and even cascade processes, with no need to adapt the reaction conditions to the reductive amination step or to purify the reaction intermediates. More details can be found in the Communication by S. Riva et al. on page 3106 in Issue 19, 2015 (DOI: 10.1002/cctc.201500424).