An alternate preparation of 5'-amino-2',5'-dideoxyguanosine (or 5'-amino-2',5'-dideoxyinosine) is to treat the protected 2'-deoxy guanosine (protected as the N-2-acetyl, the N-2-phenylacetyl, or the N-2-FMOC derivative) (1 mmol) with tosyl chloride (1.3 mmol) in pyridine at 0° C. overnight. The solution is evaporated to dryness and the residue is dissolved in chloroform. The resulting solution is washed twice with aqueous sodium bicarbonate and dried over sodium sulfate. The solvent is evaporated and the residue chromatographed on silica gel eluting with methanol/chloroform mixtures. The resulting tosylate (1 mmol) is treated with sodium azide (6 mmol) in DMF at 80°-100° C. for a few h, or lithium azide (10 mmol) in DMF at 60° C. for several h. The solvent is removed by rotovap and the residue is chromatographed on silica gel eluting with chloroform/methanol solvent mixtures. The azide is reduced to the desired amine using the above procedure.
