A series of novel conjugates of cobalt bis(1,2-dicarbollide)(-I) with 5-ethynyl-2′-deoxyuridine and its cyclic derivatives were synthesized. Conjugates with 5-ethynyl-2-deoxyuridine were prepared by the direct Sonogashira coupling of a series of cobalt bis(1,2-dicarbollide)(-I) terminal alkynes and 5-iodo-2′-deoxyuridine. Their furo2,3-dpyrimidin-2(3H)-one isomers were obtained either by intermolecular cyclization of the above conjugates or by Sonogashira coupling using Pd/C as a catalyst. Action of ammonia on these furo2,3-dpyrimidin-2(3H)-one conjugates resulted in pyrrolo2,3-dpyrimidin-2(3H)-one conjugates. Most of the designed compounds have shown low cytotoxicity in several cell lines. Some 5-ethynyl-2-deoxyuridine and furo2,3-dpyrimidin-2(3H)-one conjugates have also presented antiviral activity. Display omitted