A Photo-Enzymatic Cascade to Transform Racemic Alcohols into Enantiomerically Pure Amines

Abstract

The consecutive photooxidation and reductive amination of various alcohols in a cascade reaction were realized by the combination of a photocatalyst and several enzymes. Whereas the photocatalyst (sodium anthraquinone-2-sulfonate) mediated the light-driven, aerobic oxidation of primary and secondary alcohols, the enzymes (various ω-transaminases) catalyzed the enantio-specific reductive amination of the intermediate aldehydes and ketones. The system worked in a one-pot one-step fashion, whereas the productivity was significantly improved by switching to a one-pot two-step procedure. A wide range of aliphatic and aromatic compounds was transformed into the enantiomerically pure corresponding amines via the photo-enzymatic cascade.

Photo‐biocatalytic Cascades: Combining Chemical and Enzymatic Transformations Fueled by Light

“…Reaction conditions: SAS (0.75 mM), substrate (10 mM), crude cell extract containing ω‐TA (10 mg/mL), IPA (1 M), PLP (1 mM) in phosphate buffer (50 mM). Samples were incubated at 30 °C under visible light illumination [111] …”

“…Samples were incubated at 30°C under visible light illumination. [111] for the amine racemization since these catalysts often perform under different conditions. Zhou and co-workers demonstrated the combination of enzymatic DKR with photo-redox mediated HAT for the racemization of amines (Scheme 12B).…”

“…Recently, Hollmann and co-workers developed a one-pot sequential cascade combining a light-driven oxyfunctionalization reaction using SAS as photocatalyst with a subsequent biocatalytic reductive amination by using highly selective ωtransaminases (ω-TA) from different origins (Scheme 12C). [111] Numerous photocatalysts were initially investigated to devise an optimal model reaction for the conversion of rac-1-phenylethanol to the corresponding ketone (acetophenone). According to the obtained results, the group focused their attention on SAS and heterogeneous graphitic carbon nitride (g-C 3 N 4 ).…”

Applications of Nanomaterials in Asymmetric Photocatalysis: Recent Progress, Challenges, and Opportunities

“…It is worth mentioning that this semiconductor photocatalyst‐enzyme coupling strategy could also be extended to many other semiconductors with water oxidation activity like Au–BiVO 4 , carbon nanodot (CND) and graphitic carbon nitride (g‐C 3 N 4 ), etc. [ 44–47 ]…”

Biocatalysis and Pharmaceuticals: A Smart Tool for Sustainable Development

“…In the second article producing enantiopure amines, Hollmann and coworkers report a methodology based on the aerobic photooxidation (mediated by water-soluble sodium anthraquinone-2-sulfonate (SAS) and heterogeneous graphitic carbon nitride (g-C 3 N 4 )) of primary and racemic secondary alcohols to the corresponding aldehydes and prochiral ketones, which are subsequently transformed into the (chiral) amines with commercial aminotransaminases (one (R) and four (S)-ATAs), using isopropylamine as the sacrificial amine donor [92]. The system worked in a one-pot, one-step fashion; as time-consuming intermediate isolation and purification steps were omitted, the required amount of organic solvents was minimized, with a concomitant reduction of waste.…”