The role of carboranes in medicinal chemistry has diversified in recent years and now extends into areas of drug discovery, molecular imaging, and targeted radionuclide therapy. An introduction to carborane chemistry is provided to familiarize the non-expert with some key properties of these molecules, followed by an overview of current medicinally-orientated research involving carboranes. The broad-ranging nature of this research is illustrated, with emphasis placed on recent highlights and advances in this field.

Radiolabeled biomolecules can be used to visualize a variety of diseases through interaction with specific cell receptors. A key step is the introduction of a molecular entity that allows facile labeling with the medically useful radionuclide ^99mTc without significant alteration of the structure and function of the biomolecule. One strategy focuses on the design of single amino acid chelates (SAACs), novel bifunctional chelators constructed from derivatized amino acids or amino acid analogues. The chelating terminus of the SAAC has been designed for effective coordination to the {^99mTc(CO)₃}⁺ core, while the other terminus allows incorporation into any position along a peptide sequence or into a variety of biomolecules. In applications to peptidic materials, the approach affords significant flexibility in the choice of donors for ^99mTc coordination combined with the considerable advantages of routine solid phase synthetic techniques. The methodology allows libraries of peptide-based ^99mTc(I) and ^186,188Re(I) radiopharmaceuticals to prepared using conventional automated peptides synthesis. Other biomolecules, including nucleosides, carbohydrates, folic acid and vitamin B12 are also readily modified using analogous methods. The approach also allows the preparation of isostructural ^99mTc and Re complexes for the correlation of in vivo and in vitro imaging studies.