Intermediate 10 is the same compound observed in Taylor and Jessen's 3,14 syntheses of NTPs and is therefore amenable to a variety of ring opening reactions, which were briefly investigated in one-pot procedures starting from 5. Treatment of 10 with water results in ring opening to ATP in seconds; the ATP was purified by anion exchange HPLC (AX-HPLC) yielding the ammonium salt of ATP(11, Figure ). Similarly, treatment of 10 with diethylamine resulted in γ-diethylamino-ATP, which was purified by AX-HPLC (12, Figure ). Additionally, 10 can be ring opened by treatment with UMP in the presence of MgCl2. This results in selective formation of adenosine uridine tetraphosphate (13) isolated as its ammonium salt after purification by AX-HPLC. A number of syntheses of dinucleoside tetraphosphates have been reported, and this synthesis, as well as Wright's 17 are convenient due to their high yields and utilization of NMP substrates rather than more expensive and difficult to synthesize NTPs. Furthermore, the present synthesis provides convenient access to unsymmetrical dinucleoside tetraphosphates, which is not possible with Wright's reagent. Lastly, longer nucleoside oligophosphates are competent phosphorylation substrates, albeit with reduced yield, and treatment of 5 with the TBA salt of ADP and subsequent hydrolysis yields adenosine tetraphosphate (14).