Arapen: a secondary complex between platinum ethylenediamine dichloride and cytosine arabinoside. I. Preparations and reactivity towards nucleic acid constituents.

An equimolecular complex between platinum ethylenediamine dichloride (PtenCl2) and 1-beta-D-arabinofuranosyl cytosine (araC) has been prepared (arapen). This 1 : 1 complex in which both ethylenediamine and araC moieties carried a radioactive label was found to be unreactive towards cytosine and guanine derivatives, but to react to the extent of 30% with deoxyadenosine, adenosine 5' -monophosphate, polyadenylic acid, poly a(AT) and DNA at comparable rates. It is suggested that adenine compounds react with platinum complexes such as PtenCl2 in a bidentate manner, but are still able to react with arapen as monodentate ligands. However, hydrolysis of the last chloride ion from arapen may not be complete, and the incoming adenine nucleophile is only able to react to a limited extent.