Two anti-Prelog NAD-Dependent Alcohol Dehydrogenases with Broad Substrate Scope and Excellent Enantioselectivity

Enantiomerically pure alcohols are important to produce active pharmaceutical ingredients, agrochemicals and fine chemicals. Herein, we explored the substrate scope and chemo- and enantioselectivity of two NAD-dependent anti-Prelog alcohol dehydrogenases from Candida maris (Cm-ADH) and Pichia finlandica (Pf-ADH) in the asymmetric reduction of ketones. The ADHs were tested for the reduction of acetophenone with NADH that was recycled using a formate dehydrogenase and sodium formate. Cm-ADH and Pf-ADH performed best at 30 °C and at around pH 7 and pH 6, respectively. Pf-ADH operated well at 50 mM acetophenone concentration, while Cm-ADH was limited to 10 mM. Regarding the substrate scope, linear-chain alkyl ketones were efficiently reduced (up to 98 % conversion), while branched and cyclic ketones gave lower conversions (up to 60 %). Aryl-aliphatic ketones showed variable levels of conversion (<1–79 %), while α,β-unsaturated and heteroaromatic ketones exhibited good to excellent conversions. In most of the cases, the enantiomeric excess was >99 %. Aliphatic and aryl-aliphatic aldehydes were converted with up to >99 % conversion. A scale-up experiment with Pf-ADH using acetophenone as substrate led to 73 % isolated yield and >99 % ee (R).
This work contributes to filling the gap in biocatalytic asymmetric synthesis of chiral alcohols by introducing two NAD-dependent ADHs with anti-Prelog selectivity.