Abstract α, β-Dehydroamino acid derivatives proved to be a novel substrate class for ene- reductases from the 'old yellow enzyme'(OYE) family. Whereas N-acylamino substituents were tolerated in the α-position, β-analogues were generally unreactive. For aspartic acid derivatives, the stereochemical outcome of the bioreduction using OYE3 could be controlled by variation of the N-acyl protective group to furnish the corresponding (S)-or (R)-amino ...