Design, synthesis, and anti-tumor activity of 4'-thionucleosides as potent and selective agonists at the human A3 adenosine receptor

On the basis of potent and selective binding affinity of Cl-IB-MECA to the human A(3) adenosine receptor, its 4'-thioadenosine derivatives were efficiently synthesized starting from D-gulonic gamma-lactone. Among compounds tested, 2-chloro-N(6)-(3-iodobenzyl)- and 2-chloro-N(6)-methyl-4' -thioadenosine-5' -methyluronamides (7a and 7b) exhibited nanomolar range of binding affinity (K(i) = 0.38 nM and 0.28 nM, respectively) at the human A(3)AR. These compounds showed anti-growth effects on HL-60 leukemia cell, which resulted from the inhibition of Wnt signaling pathway.