highly purified fractions from human urine exhibiting antineoplastic activity and processes for their preparation are described . the fractions comprise biologically active , small sized , low molecular weight peptides which exert cytostatic and cytotoxic activity toward neoplastic cell cultures and human neoplastic diseases . the fractions have been termed antineoplaston fractions . an antineoplastic active peptide common to each of the various antineoplaston fractions has been isolated and identified as 3 -- 2 , 6 - dion . a synthetic mechanism for the preparation of 3 -- 2 , 6 - dion is also disclosed , involving a combination reaction between l - glutamine and phenylacetyl chloride . also disclosed are the hydrolysis degradation products of 3 -- 2 , 6 - dion which also exhibit antineoplastic activity when administered according to the general teachings presented in this disclosure .