The synthesis of (lb) from (2a) and 2,6-dichloropurine in six steps using an enzymatic deamination as the last step is reported. The target compound was found to be stable to purine nucleoside phosphorylase cleavage and was cytotoxic in two cell lines, one a T-cell line. Incubation of L1210 cells with lb results in an inhibition of DNA synthesis as judged by the reduced incorporation of labeled thymidine into DNA, while RNA and protein syntheses were unaffected. © 1986, American Chemical Society. All rights reserved.