Synthesis of new nucleoside phosphoraziridines as potential site-directed antineoplastic agents

Article abstract of DOI:10.1021/jm00171a039

With the aim of increasing the selectivity of the 2,2-dimethylphosphoraziridine type antitumor agents towards the intracellular site of DNA synthesis, a series of new compounds was synthesized in which the reactive bis(2,2-dimethyl-1-aziridinyl)phosphinyl (2,2-DMAP) group was linked through a carbamate or amide linkage to thymidine or cytosine nucleoside moieties. The 3'- and 5'-(2,2-DMAP)carbamates of thymidine (1 and 2) were found to be highly unstable, therefore the corresponding O-acetyl derivatives 5 and 6 were prepared by reacting 5'- and 3'-acetylthymidine, respectively, with dichloroisocyanatophosphine oxide followed by the addition of 2,2-dimethylaziridine and triethylamine. The 3'- and 5'-(2,2-DMAP)amides of thymidine 14 and 15 were prepared by reacting the appropriate thymidinylamines with bis(2,2-dimethyl-1-aziridinyl)phosphinyl chloride (17). The N⁴-(2,2-DMAP)amides of cytidine, 2'-deoxycytidine, and cytosine arabinoside (18, 19, and 20, respectively) were prepared by reacting the hydrochlorides of the O-peracetylated cytosine nucleosides with triethylamine and POCl₃ and, subsequently, with 2,2-dimethylaziridine and triethylamine, to give the corresponding N⁴-(2,2-DMAP)cytosine nucleoside peracetates 21, 22, and 23, respectively, which were then deacetylated by aminolysis. However, the peracetate intermediates were found to be more stable and, probably for the same reason, also more active against P388 leukemia in mice than the deacetylated products. Particularly, 22 and 23 showed sufficient activity in this in vivo assay system to warrant further evaluation. The relationships between the antitumor activities, the chemical alkylating activities, and the cholinesterase inhibitory activities of these agents are discussed.