Scheme 1.

Enzymatic reaction schemes for the selective oxidation of trans-hex-2-enol. A: Alcohol dehydrogenase (ADH)-catalysed oxidation producing stoichiometric amounts of NAD(P)H, which needs to be recycled in situ; the overall reaction is reversible requiring surpluses of the cosubstrate (e.g., acetone) to shift the overall equilibrium to the side of trans-hex-2-enal. B: Envisioned aerobic oxidation using alcohol oxidases (AOx). H₂O₂ is formed as byproduct and dismutated by catalase into H₂O and O₂.