Mechanism of action of the nitrosoureas--IV. Synthesis of the 2-haloethylnitrosourea-induced DNA cross-link 1-(3-cytosinyl),2-(1-guanyl)ethane.

The 2-haloethylnitrosoureas have been shown to form the cross-linked structure 1-(3-cytosinyl),2-(1-guanyl)ethane in DNA. This cross-link has now been synthesized by the reaction of O6-(2-fluoroethyl)guanosine with deoxycytidine in dimethyl sulfoxide followed by removal of the sugars by acid hydrolysis. This synthetic route supports the mechanism for cross-link formation in DNA that involves an initial attack on the O6-position of guanine, followed by a rearrangement and subsequent reaction with cytosine. It also provides a practical route to the synthesis of 1-(3-cytosinyl),2-(1-guanyl)ethane for studies involving formation of this cross-link in DNA.