New and efficient routes to biomolecules substituted with cyclopentadienyltricarbonylrhenium and -technetium derivatives

The small, compact, robust, and nonpolar units of [CPM(CO)(3)] (M = Re, Tc) coupled with biomolecules may be considered as bioorganometallic entities of potential interest in the field of medicinal chemistry However, the shor t half-life of useful radionuclides (Re-186 t(1/2) = 3.7 d, Re-188 t(1/2) = 16.8 h, Tc-99m t(1/2) = 6 h), the risks inherent in their use, and their co st have led chemists to search for novel synthetic strategies that allow th e rapid introduction of the [CpM(CO)(3)] moiety as a late step in the cours e of synthesizing the target molecule. The present paper describes differen t strategies recently reported in the literature to tackle this problem.