Synthesis of complex ethynyladenosines using organic triflic enolates in palladium-catalyzed reactions: Potential agonists for the adenosine A(2) receptor

Many high affinity adenosine Al receptor agonists contain substituents at position 2 of the purine base. In the search for new methodology to develop C-2 substituted adenosine analogues, we have applied organic triflates in palladium-catalyzed cross-couplings that resulted in new 2-cycloalkylated ethynyladenosines. The organic triflates are derived from commercially available ketones and, when used in the cross-couplings, result generally in clean reactions with good yields. These are the first examples of the utilization of organic triflates in palladium-catalyzed cross-coupling reactions in the synthesis of modified nucleosides. (C) 1997 Elsevier Science Ltd.