A new efficient approach for the preparation of 188Re radiopharmaceuticals starting from [188ReO4]-, produced at a carrier- free level through the 188W/188Re generator system, is described. The reaction procedure was based on the combined action of different reagents and has been applied in detail to the preparation of the therapeutic agent 188Re(V)-DMSA (H2DMSA [meso-2,3-dimercaptosuccinic acid]). The most efficient combination required the use of SnCl2, oxalate ions, and γ- cyclodextrin. These were reacted with [188ReO4]- and H2DMSA to afford the final radiopharmaceutical in high radiochemical purity, at room temperature, and in weakly acidic solution. The role played by the various reagents in the reaction was investigated. It was found that SnCl2 behaved as the actual reducing agent, whereas oxalate and γ-cyclodextrin greatly enhanced the ease of reduction of [188ReO4]- through the action of two hypothetical mechanisms. In the first step of the reaction, oxalate ions gave rise to the formation of Re(VII) complexes with the concomitant expansion of the coordination sphere of the metal. This process strongly favored the electron transfer between Sn2+ and Re+7 centers, giving rise to intermediate reduced rhenium complexes. These species were further stabilized by the formation of transient host-guest aggregates with γ-cyclodextrin and finally converted into 188Re(V)-DMSA through simple replacement of the coordinated ligands by H2DMSA. (C) 2000 Elsevier Science Inc.
An alternative approach to the preparation of (188)Re radiopharmaceuticals from generator-produced [(188)ReO(4)]:(-) efficient synthesis of (188)Re(V)-meso-2,3-dimercaptosuccinic acid
DUATTI, Adriano;UCCELLI, Licia;BOSCHI, Alessandra;
2000
Abstract
A new efficient approach for the preparation of 188Re radiopharmaceuticals starting from [188ReO4]-, produced at a carrier- free level through the 188W/188Re generator system, is described. The reaction procedure was based on the combined action of different reagents and has been applied in detail to the preparation of the therapeutic agent 188Re(V)-DMSA (H2DMSA [meso-2,3-dimercaptosuccinic acid]). The most efficient combination required the use of SnCl2, oxalate ions, and γ- cyclodextrin. These were reacted with [188ReO4]- and H2DMSA to afford the final radiopharmaceutical in high radiochemical purity, at room temperature, and in weakly acidic solution. The role played by the various reagents in the reaction was investigated. It was found that SnCl2 behaved as the actual reducing agent, whereas oxalate and γ-cyclodextrin greatly enhanced the ease of reduction of [188ReO4]- through the action of two hypothetical mechanisms. In the first step of the reaction, oxalate ions gave rise to the formation of Re(VII) complexes with the concomitant expansion of the coordination sphere of the metal. This process strongly favored the electron transfer between Sn2+ and Re+7 centers, giving rise to intermediate reduced rhenium complexes. These species were further stabilized by the formation of transient host-guest aggregates with γ-cyclodextrin and finally converted into 188Re(V)-DMSA through simple replacement of the coordinated ligands by H2DMSA. (C) 2000 Elsevier Science Inc.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
