Synthesis and biologic evaluation of major metabolites of N-(2-chloroethyl)-N'-cyclohexyl-N-nitrosourea.

N-(2-chloroethyl)-N'-(cis-4-hydroxycylohexyl)-N-nitrosourea, a major metabolite of N-(2-chloroethyl)-N'-cyclohexyl-N-nitrosourea (CCNU), and its trans isomer were prepared from the corresponding 4-aminocyclohexanols. A convenient and stereospecific precursor was found in 2-oxa-3-azabicyclo[2.2.2]oct-5-ene hydrochloride, hydrogenation giving pure cis-4-aminocyclohexanol hydrochloride. The metabolites were, at nontoxic levels, at least as active as CCNU in tests against murine leukemia L1210 implanted both intraperitoneally and intracerebrally and, on a weight basis, were more active and more toxic. These observations and previously reported metabolic studies suggest that the anticancer activity of CCNU is due primarily to its metabolites.