Further studies on the substrate specificity of calf spleen phosphodiesterase [EC 3.1.4.18

The synthesis of 5'-deoxy-5'-chlorothymidine-3'-(4-nitrophenyl)phosphate (5) and 5'-deoxy-5'-chlorothymidine-3'-(4-nitrophenyl)phosphorothioate (6) via corresponding phosphoranilidodiester intermediate is described. The affinity of 5 and 6 towards SPDE in comparison with thymidine-3'-(4-nitrophenyl)phosphate is tested. These findings reveal that the presence of 5'-hydroxyl function in the substrate is not necessary for hydrolytic action of this enzyme.