249757-27-5Relevant articles and documents
First evident generation of purin-2-yllithium: Lithiation of an 8-silyl- protected 6-chloropurine riboside as a key step for the synthesis of 2- carbon-substituted adenosines
Kumamoto, Hiroki,Tanaka, Hiromichi,Tsukioka, Ryota,Ishida, Yumiko,Nakamura, Akiko,Kimura, Satoe,Hayakawa, Hiroyuki,Kato, Keisuke,Miyasaka, Tadashi
, p. 7773 - 7780 (1999)
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 substrate and LTMP as a lithiating agent. The 8-triisopropylsilyl group in 7 did not undergo anionic migration and, thus, allowed the ready generation of the C2-lithiated species by preventing deprotonation at the 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-chlorine atom of these products (heating at 110 °C in a sealed tube with NH3/MeOH) effected simultaneous desilylation at the 8- position to give the corresponding adenosine analogues. The whole sequence provides a new and highly general method for the synthesis of 2-substituted adenosines.