Isolation of cis- and trans-4-methylcyclophosphamide and antitumor evaluation in vivo.

4-Methylcyclophosphamide was synthesized and separated into cis and trans isomers by column chromatography. Isolation of these isomers permitted individual evaluation against murine leukemia L1210 in vivo and assessment of possible differences in antileukemic activity. Results indicate no appreciable difference in activity of the isomers, suggesting essentially equal facility for activation by mouse liver microsomes in vivo.