Editorial

Boron is a unique non-metallic element with the ability to combine with itself and many other elements to form compounds of extreme structural diversity and unusual properties. Boron exists in nature as a mixture of two stable isotopes, 10B (19.8%) and 11B (80.2%); the former possesses an extremely high cross-section for neutron capture (3,840 barns), producing high-energy alpha particles and recoiling lithium nuclei, according to the 10B(n,a)7Li nuclear reaction. The discovery of boron clusters of remarkably high boron content in the 1950s and 1960s has widened their application in various fields, mainly in medicinal chemistry as radiolabeling and tumor treatment agents. The exceptional stabilities of boron clusters, their unique hydrophobic and potential amphiphilic properties, and the ability of the opencage clusters to form sandwich complexes with a variety of metals, have led to the development of many interesting molecules for application in tumor imaging and treatment using boron neutron capture therapy (BNCT). Despite extraordinary advances in the last decades on the synthesis and chemistry of boron compounds and their enrichment in the 10B isotope at ∼95% levels, BNCT is still in the early stages of its practical development. One of the main challenges to the BNCT modality continues to be the discovery of uniquely tumor-selective agents, capable of delivering therapeutic concentrations of 10B to target tumors, with low toxicity and high specificity. In this Special Issue of Current Medicinal Chemistry - Anti Cancer Agents, the main classes of boron-containing molecules and the current state-of-the- art in compound design and characterization are reviewed. The scourge of cancer is still with us, but never before has there been such an exciting time in the development of multi-faceted boron molecules for application in medicinal chemistry, and particularly for the treatment of cancer