O-Methylhydroxylamine as a New Trapping Reagent for Quantitative Studies of 4-Hydroxycyclophosphamide and Aldophosphamide

Abstract

31P- and 1H-NMR spectroscopy were used to demonstrate that the primary metabolites of the anticancer drug cyclophosphamide (4-hydroxycyclophosphamide and its acyclic tautomer, aldophosphamide) are quantitatively converted by O-methylhydroxylamine, at pH 7.4 and 37o, into the E and Z isomers of aldophosphamide O-methyl oxime. These trapping products are readily extracted from aqueous media with either chloroform or ethyl acetate, are stable at pH 6-8 toward oxime hydrolysis and elimination of phosphoramide mustard (a secondary metabolite of cyclophosphamide), and showed no evidence for transox-imination with either ketone or aldehyde acceptors. All of these features support the use of aldophosphamide O-methyl oxime in quantitative studies related to cyclophosphamide metabolism.