Synthesis of Substituted 5′-Aminoadenosine Derivatives and Evaluation of Their Inhibitory Potential toward CD73

Derivatives of 5 '-aminoadenosine containing methyl carboxylate, methyl phosphonate, gem-bisphosphonate, bis(methylphosphonate), and alpha-carboxylmethylphosphonate or phosphonoacetate moieties were synthesized from key intermediate 5 '-aminonucleoside. These nucleotide analogues were envisaged as 5 '-mono- or diphosphate nucleoside mimics. All compounds were evaluated for CD73 inhibition in a cell-based assay (MDA-MB-231) and toward the purified recombinant protein. Most of them failed to reach significant inhibition of AMP hydrolysis by CD73 at 100 mu m. Among the new compounds, the most interesting candidates, 5 (5 '-deoxy-5 '-N-phosphonomethyladenosine) and 7 (5 '-deoxy-5 '-N-(ethoxyphosphorylacetate)adenosine), inhibited recombinant CD73 by 36 and 46 % and cellular CD73 by 61 and 45 % at 100 mu m, respectively. Molecular modeling partially explains this lack of activity, as the initially predicted docking scores had been encouraging, especially for compound 9.