ABSTRACT
Physicochemical versatility combined with chemical reactivity and high stability under physiological conditions make boron clusters very attractive choices for a variety of applications including conventional drug design and development (Armstrong and Valliant, 2007; Lesnikowski, 2009), boron neutron capture therapy (BNCT) (Sivaev et al., 2002; Soloway et al., 1998; Tjarks, 2000; Tolmachev and Sjöberg, 2002), and, in the case of (radio)halogenated boron clusters, tumor imaging and therapy (Armstrong and Valliant, 2007; Hawthorne and Maderna, 1999). In BNCT, radiohalogenation of boron clusters has been used to explore pharmacokinetic pro™les of boronated tumortargeting agents (Chen et al., 1994; Mizusawa et al., 1985; Paxton et al., 1992; Varadarajan et al., 1991), whereas other research efforts in this area were directed to more general applications in
6.1 Introduction .......................................................................................................................... 107 6.2 Cold Boron Cluster Halogenation ......................................................................................... 109
6.2.1 Neutral Boron Clusters ............................................................................................. 109 6.2.1.1 1,2-Dicarbadodecaborane (o-Carborane) .................................................. 109 6.2.1.2 1,7-Dicarbadodecaborane (m-Carborane) .................................................. 113 6.2.1.3 1,12-Dicarbadodecaborane (p-Carborane) ................................................ 115 6.2.1.4 Preparation of Halogenated Carboranes by Halogen Exchange ................ 115
6.2.2 Anionic Boron Clusters ............................................................................................ 118 6.2.2.1 7,8-Dicarbaundecaborate (1-) (nido-o-Carborane Anion) ......................... 118 6.2.2.2 1-Carbadodecaborate (1-) ........................................................................... 119
6.2.3 Dodecahydro-closo-Dodecaborate (2-) and Decahydro-closo-Decaborate (2-) ...... 120 6.3 Radiohalogenation of Boron Clusters .................................................................................. 123
6.3.1 Radiohalogenation by Oxidative Agents .................................................................. 123 6.3.1.1 Radioiodination .......................................................................................... 123 6.3.1.2 Radioastatination ....................................................................................... 129 6.3.1.3 Radiobromination ...................................................................................... 136
6.3.2 Radiohalogenation by Catalytic Halogen Exchange................................................. 136 6.3.2.1 Radiohalogenation of Simple Carboranyl Structures ................................ 137 6.3.2.2 Radioiodination of 3-Carboranyl Thymidine Analogs (3CTAs)
through Isotope Exchange ......................................................................... 138 Acknowledgment ........................................................................................................................... 139 References ...................................................................................................................................... 139
tumor imaging and therapy (Armstrong and Valliant, 2007; Bruskin et al., 2004; Green et al., 2008; Hawthorne and Maderna, 1999; Shchukin et al., 2004; Tran et al., 2007; Wilbur et al., 2004d; Winberg et al., 2004).
