Scheme 6.

Synthesis of Isopentenyl Bisphosphate, Compound 10^a

^a Reaction conditions: (i) EtO₂CCH₂P(O)(OEt)₂, NaH, THF, rt, 2 h, 85%; (ii) DIBAL, toluene, −78 °C to rt, 1 h, 74%; (iii) 2,6-chloropurine, DEAD, PPh₃, THF, rt, 2 h, 57%; (iv) CH₃NH₂, THF, rt, 6 h, 85%; (v) AcOH:H₂O:THF = 1:2:2, 40 °C, 5 h, 86%; (vi) Et₂NP(OtBu)₂, tetrazole, THF, rt, 1 h then MCPBA, 35%; (v) Dowex 50x-8 200, MeOH/H₂O = 1:1, 50 °C, 3 h, 63%.