| Abstract
| - Lithiation at the 2-position of purine ring has been accomplished for the first time by using 6-chloro-9-(2,3-O-isopropylidene-5-O-trityl-β-d-ribofuranosyl)-8-(triisopropylsilyl)purine (7) as a substrateand LTMP as a lithiating agent. The 8-triisopropylsilyl group in 7 did not undergo anionic migrationand, thus, allowed the ready generation of the C2-lithiated species by preventing deprotonation atthe 8-position. The electron-withdrawing 6-chlorine atom plays an essential role to this C2-lithiation.Reactions of the lithiated species with electrophiles gave the 2-substituted products (Me, Et, i-Pr,CH(OH)C6H11, C(OH)Me2, CHO, CO2Me, and I) mostly in good yields. Ammonolysis of the 6-chlorineatom of these products (heating at 110 °C in a sealed tube with NH3/MeOH) effected simultaneousdesilylation at the 8-position to give the corresponding adenosine analogues. The whole sequenceprovides a new and highly general method for the synthesis of 2-substituted adenosines.
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