Purine analogues represent an excellent scaffold for
targeting many biosynthetic, regulatory, and signal transduction
proteins including cellular kinases, G proteins, and
polymerases.1 Purine core compounds, especially the 2,6,9-
substituted purines, act as potent inhibitors of Hsp90, Src
kinase, P38R MAP kinase, sulfotransferases, phosphodiesterases,
and Cdks.2 Accordingly, the developement of more
efficient, convenient, and environmentally friendly methods
for the synthesis of 2,6,9-substituted purines is important.
2,6,9-Substituted purines were synthesized previously by
Fiorini et al. using solution-phase synthetic approaches with
2,6-dichloropurine as the starting material.3 However, this
synthetic process needs a long heating time and complicated
reaction conditions. Subsequently, several solid-phase synthesis
methods were developed,4 but the substitution at the
C2 position was difficult. To expand the diversity of the N9
position of purine, Ding et al. employed a copper(II)-
mediated coupling reaction to prepare 9-arylpurines with
yields of 43-47%.5 The coupling reaction has emerged as a
valuable method for the preparation of 9-arylpurines, but long
reaction times are required.