Alkylation of adenine (5a) or 2-amino-6-chloropurine (5b) with excess trans-1,4-dichloro-2-butene (4), effected by K2CO3 in dimethyl sulfoxide or tetra-n-butylammonium fluoride in tetrahydrofuran, led in 90-95% regioselectivity to 9-alkylpurines 6a and 6b. The title compounds 2a and 2b were obtained by refluxing intermediates 6a and 6b in 0.1 M NaOH or HCl. Adenine derivative 2a is a substrate for adenosine deaminase whereas both 2a and 2b exhibit 50% inhibition of the growth of murine leukemia L 1210 cell culture at 1 mM concentration.