6-Ethyl(methyl)aminopurine was prepared by nucleophilic displacement of the chlorine group on 6-chloropurine (Sigma Chemicals, St. Louis, Mo.) by ethylo(methyt)amine in acetonitrile. 6-Ethyl(methyl)aminopurine (2.8 mmoles, 0.5 g) and uracil arabinoside (5.6 mmoles, 1.38 g) were suspended in 575 ml of a 10 mM potassium phosphate, 0.04% potassium azide solution, pH of 7.4, containing 10% n-propanol (v/v). Purified uridine phosphorylase (6000 I.U.) and purine nucleoside phosphorylase (8400 I.U.) (Krenitsky, T. A. et al., Biochemistry, 20, 3615 (1981) and U.S. Pat. No. 4,381,344) were added and the solution stirred at 37° C. Nineteen days later the reaction was filtered and the filtrate chromatographed on a 2.5×13 cm column containing Dowex-1-hydroxide resin. The resin was eluted with 90% methanol/water (v/v). Fractions containing the product were combined and the solvent removed under vacuum. The residue was dissolved in 30% n-propanol/water (v/v) and chromatographed on BioRad P-2 column (7.5×90 cm). Product containing fraction were combined and after lyophilization yielded 0.680 g of 9-β-D-arabinofuranosyl-6-ethyl(methyl)amino-9H-purine. NMR and mass spectrometry were consistent with the structure. Anal. Calcd. for C13H19N5O4 : Calcd: C,50.48; H,6.19; N,22.64. Found: C,50.36; H,6.25; N,22.52.
