THE ANHYDROUS RACEMATE OF THE CARCINOSTATIC AGENT CYCLOPHOSPHAMIDE AND THE BICYCLIC DEGRADATION PRODUCT ,3,2-DIAZA-PHOSPHOLO[2,1-B][1,3,2]OXAZAPHOSPHORINE 9-OXIDE

Anhydrous racemic cyclophosphamide, ethyl)-tetrahydro-2H-1,3,2-oxazaph osphorin-2-amine 2-oxide, C7H15Cl2N2O2P, (1)], displays a chair confor mation with an axial phosphoryl O atom and approximately planar geomet ry at the N atoms. The molecules are linked by N-H ... O=P hydrogen bo nds into chains. One chloroethyl side chain is extended, the other is gauche. The C-Cl bond lengths are Cl1-C5 1.789(2) and C12-C7 1.791(2)A . The bicyclic degradation product, 1,3,2-diazaphospholo[2,1-b][1,3,2] oxazapgisogirube 9-oxide, C7H14ClN2O2P, (2), is formed by intramolecul ar alkylation at the ring N atom of (1). The major change of bond leng th upon annelation is observed for P-N2, the ring P-N bond in (1), whi ch is lengthened from 1.633 (2) to 1.6593 (14) Angstrom. The angle N1- P-N2, incorporated into the five-membered ring in (2), narrows from 10 5.84(8) to 97.36(7)degrees. The remaining chloroethyl side chain is ga uche. The C-Cl bond length is 1.790 (2) Angstrom.