Novel 5-chloro and 5-alkylsulfonate-1,3,2- oxazaphosphorine and 3-chloro-1,5,2-oxazaphosphorine derivatives, which are proposed as biological alkylating agents will be synthesized for screening as improved anticancer drugs. Possible enantiomer-specific cytotoxicity for these new chiral systems and for the known anticancer drug cyclophosphamide will also be studied by screening tests on stereospecifically synthesized samples of individual enantiomers. Various benzannelated and other diverse cyclophosphamide analogs containing oxidatively reactive ringcarbon centers will also be prepared for testing with regard to increased anticancer activity.