An Efficient Synthesis of 3′‐Amino‐3′‐deoxyguanosine from Guanosine

3′‐Amino‐3′‐deoxyguanosine was synthesized from guanosine in eight steps and 58% overall yield. The 2′,3′‐diol of 5′‐ O ‐[( tert ‐butyl)diphenylsilyl]‐2‐ N ‐[(dimethylamino)methylidene]guanosine was reacted with α ‐acetoxyisobutyryl bromide and treated with 0.5 n NH 3 in MeOH to yield 9‐{2′‐ O ‐acetyl‐3′‐bromo‐5′‐ O ‐[( tert ‐butyl)diphenylsilyl]‐3′‐deoxy‐ β ‐ D ‐xylofuranosyl]‐2‐ N ‐[(dimethylamino)methylidene]guanine, which was reacted with benzyl isocyanate, NaH, and then 3.0 n NaOH, and finally with Pd/C (10%) and HCO 2 NH 4 in EtOH/AcOH to afford 3′‐amino‐3′‐deoxyguanosine.