Facile Synthesis of Fluorinated Purines and Thiapurines - Iaroshenko, Viktor O; Volochnyuk, Dmitriy M; Yan, Wang; Vovk, Mikhail V; Boiko, Vyacheslav J; Rusanov, Eduard B; Groth, Ulrich M; Tolmachev, Andrei A (Synthesis, 2007)