X-Ray crystallographic determination of the molecular structures of cis- and trans-isomers of (±)-5-fluorocyclophosphamide {2-[bis-(2-chloroethyl)amino]-5-fluorotetrahydro-2H-1,3,2-oxazaphosphorine 2-oxide]}

The crystal and molecular structures of the cis- and trans-isomers of (±)-5-fluorocyclophosphamide have been determined by X-ray methods. The two independent molecules of the trans-isomer have almost identical conformations, with a distorted half-chair ring pucker. The cis-isomer has a boat ring conformation.