diphosphate dependent enzyme 2‐keto aciddecarboxylase (KdcA) from Lactococcus lactis is able to transfer formyl units to aliphatic and aromatic aldehydes, both in an electrophilic and in a nucleophilic way. We have established the formation of unstable chiral 2‐hydroxyaldehydes by subsequent modifications (chemical derivatisation with 2,4‐dinitrophenylhydrazine, (R)‐Mosher's acid chloride) or by enzymatic