Antineoplaston AS2-5 (AS2-5) can be obtained in the following way (1,2): N-Phenylacetyl-L-glutamine sodium is synthesized in two steps. In the first step, phenylacetic acid (I) is treated with N-hydroxysuccinimide (B) and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (A) in acetonitrile to give intermediate (Ia). In the second step, (Ia) is reacted without purification with L-glutamine (II) in the presence of NaHCO3 in 1:1 acetonitrile-water mixture to afford N-phenylacetyl-L-glutamine (III) in 87% yield. Compound (III) is then converted to sodium salt in aqueous solution by treatment with aqueous sodium hydroxide solution (pH 7). In a large scale preparation reaction of phenylacetyl chloride with L-glutamine in aqueous solution containing NaHCO3 affords N-phenyiacetyl L-glutamine sodium.