Synthesis of deuterium-labeled analogs of cyclophosphamide and its metabolites

Convenient syntheses are described of d4 analogs of cyclophosphamide and some of its metabolites, potential standards for the quantitative analysis of the drug and its metabolites in human body fluids by stable isotope dilution-mass spectrometry. Base-catalyzed H-D exchange on N-nitrosobis(2-hydroxyethyl)amine gave N-nitrosobis(1,1-dideuterio-2-hydroxyethyl)amine from which bis(2-chloro-1,1-dideuterioethyl)amine (nor-HN2-d4) was readily obtained. Established synthetic routes were then used to convert nor-HN2-d4 into d4 analogs of cyclophosphamide [2-[bis(2-chlorethyl)amino]tetrahydro-2H-1,3,2-oxazaphosphorine 2-oxide], 4-ketocyclophosphamide [2[BIS(2-chloroethyl)amino]tetrahydro-2H-1,3,2-oxazaphosphorin-4-one 2-oxide], and carboxyphosphamide [2-carboxyethyl N-N-bis(2-chloroethyl)phosphorodiamidate], and these analogs were used in a preliminary investigation into the quantitation of the appropriate components in human plasma and urine. Also prepared were d4 analogs of phosphoramide mustard [N,N-bis(2-chloroethyl)phosphorodiamidic acid (cyclohexylammonium salt)] and 3-(2-chloroethyl)oxazolidone and the methyl and trideuteriomethyl esters of phosphoramide mustard.