Synthesis and Absolute Configuration of the Optically Active Forms of 2-[Bis(2-chloroethyl)amino]-4-methyltetrahydro-2 H-1, 3, 2-oxazaphosphorine 2-Oxide (4-Methylcyclophosphamide)

The cytochrome P450 mediated oxidation of the antitumor agent 2-[bis(2-chloroethyl)amino]tetrahydro-2H-1, 3, 2-oxazaphosphorine 2-oxide (cyclophosphamide 1) to give the 4-hydroxy derivative is well documented1 and has prompted many detailed investigations.2 4-Methylcyclophosphamide (2) is of interest since the methyl group prevents further oxidative metabolism of the 4-hydroxy derivative.3 The isolation and configurational assignment of the cis and trans forms of 4-methylcyclophosphamide (2) has been described recently by Struck et al.4 We now report evidence which indicates that these configurational assignments are erroneous and also describe the synthesis of the optically active forms of cis- and trans-4-methylcyclophosphamide.