In vitro reaction of N-n-butyl-N-nitrosourea and n-butyl methanesulphonate with guanine and thymine bases of DNA.

The reaction of N-n-butyl-N-nitrosourea ( BNU ) and n-butyl methanesulphonate (BMS) with DNA has been investigated. In addition to the expected n- butylpurines formed on reaction with BNU some rearranged sec-butyl-adducts were also observed, indicating that a carbonium ion is involved in the alkylation process by nitrosoureas. Only n-butyl adducts were observed following reaction with BMS. The reaction of these alkylating agents with the thymine residues in the DNA was also determined. The relative amounts of the various adducts formed by the two butylating agents are similar to those formed by the corresponding ethyl and propyl compounds.