Towards new rhenium and technetium radiopharmaceuticals with pyrazolyl ligands

• Main Author: Salichou, Maria
• Published: University of Oxford 2007
• Subjects: 615
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491980

The continuing interest in the coordination chemistry of the group VII elements rhenium and technetium reflects the application of their radionuclides to the development· of new radiopharmaceuticals. Technetium-99m has become the radioisotope of choice in diagnostic nuclear medicine because of its ideal nuclear properties and its availability as pertechnetate. There is much interest in the development of new radiotherapeutic cancer agents based on the p-emitting isotopes of rhenium. Such targeting can be achieved by the incorporation of the metal atom in a co-ordination complex. involving a bifunctional ligand. This ligand must form a highly stable complex and possess a point of further functionalisation that can allow the attachment of biologically active molecules thus providing specificity and selectivity in vivo. Pyrazolylmethane ligands are attractive candidates for the development of new radiopharmaceuticals due to their versatility but there have been few reports oftheir complexes with rhenium. This work presents a systematic study on the co-ordination chemistry of pyrazolylmethane ligands with rhenium (i.e [ReOCh(PPh3)2], ReNCMe(NNE)(Clz)(PPh3)2] (E = Ph, naph), [Re(NNCOE)Clz(PPh3)2] (E = Ph, naph) (Chapters 2 and 3). Convenient one-pot synthetic procedures for the preparation of the rhenium (V) pyrazolyl complexes have been developed directly from perrhenate (Chapter 4). In addition a variety of synthetic routes towards the incorporation of a biologically active molecule have been explored, and the synthesis of potentially target specific complexes directly from perrhenate is reported in Chapter 5. Functionalisation of the pyrazolylmethanes to increase their denticity and to provide a site for further co-ordination with a biologically active molecule or a fluorescent probe led to the synthesis of a new class of ligands. Their co-ordination chemistry with rhenium was studied (Chapter 6). Fluorescent rhenium pyrazolyl complexes in oxidation states V - I have been designed and synthesized in order to monitor their behaviour in vitro. The 99mTc labelled pyrazolylmethane analogues have also been made and their biodistribution has been evaluated in vivo (Chapter 7). A conclusion based on the results described in chapters 2 - 7 is presented in Chapter 8. The experimental procedures followed for this work are presented in Chapter 9.