714 Journal of Medicinal Chemistry, I9 73, Vol. 16, No. 6 Notes modification of the method of Hoard and Ott” was used to prepare the triphosphate. The tripentylammonium salt of 5 (0.1 mmol) was dissolved in 3 ml of dry DMF and to this solution was added 160 mg (1.0 mmol) of l, l'-carbonyldiimidazole. The mixture was allowed to stand overnight and then treated simultaneously with MeOH (73 MI, 1.8 mmol) and tripentylammonium pyrophosphate (1.0 ...