Total Synthesis of Q Base (Queuine)

The total synthesis of Q Base (Queuine) has been accomplished in eleven steps from ribose. Mitsunobu reaction of nosyl protected amine 12 with known cyclopentenol 7, derived from ribose, gave 13, the first key intermediate in the synthesis. The pyrrolo[2,3-d]pyrimidine ring system of Q Base was built via a cyclocondensation reaction between a β-aminobromoaldehyde 16, derived from the Mitsunobu product 13, and 2,4-diamino-6-hydroxypyrimidine. Deprotection of the product from the cycloccondensation reaction (17) gave Q Base.