Effect of acylated amino acids and acylated amino acid analogs on microbial antitumor screen

A series of N-acetyl,-N-propionyl, and N-chloroacetyl derivatives of amino acids and amino acid analogs was tested for growth-inhibitory activity using a Lactobacillus casei system as a prescreen for possible antitumor activity. While none of the acetyl or propionyl derivatives of these amino acids and amino acid analogs caused any remarkable inhibition, certain chloroacetyl derivatives exhibited significant activity. The chloroacetyl derivatives, especially those of essential amino acids and of analogs of essential amino acids, showed modest, but pharmacologically significant, inhibition; those of nonessential amino acids exhibited no activity. When two such inhibitory acyl derivatives were combined in a single assay, the extent of inhibition was neither additive nor synergistic but was that of the more active of the two test components.