Racemic synthesis and enantiomeric conversion of [1‐13C] valine

A Strecker synthesis of isobutyraldehyde, K13CN and ammonia produced D,L-[1-13C] valine in 83% yield. This racemic mixtue was then converted to the L-form via a D-amino acid oxidase - branched amino acid aminotransferase system in an overall yield of 75% based on K13CN. Given the generality of the Strecker synthesis as well as the broad substrate specificity of the oxidase and aminotransferase enzymes, it is anticipated that this procedure will be comparably efficient for most standard aliphatic and aromatic amino acids.