N-acetyl-beta-phenylalanine has been produced by the reaction of phenylacetaldehyde, acetamide and CO/H-2 in the presence of cobalt carbonyl catalyst. N-acetyl-beta-phenylalanine yields of 72-82 mol% and cobalt recoveries of 98% had been achieved under the conditions of 2000 psi of 3 : 1 CO/H-2 and 80 degrees C in a batch process. The presence of a suitable ligand, 1,2-bis(diphenylphosphino)ethane, was essential for maintaining cobalt in homogeneous solution. The feasibility of using a continuous phase reactor with a dual feed stream system was demonstrated. N-acetyl-beta-phenylalanine is proposed to be the precursor to L-phenylalanine, the key intermediate for aspartame sweetener.