Solution behavior of a sugar-based carborane for boron neutron capture therapy: A nuclear magnetic resonance investigation

The physico-chemical properties of β-lactosyl-closo-orthocarborane in water solution were investigated by multinuclear NMR, ¹³C NMR relaxation, and ab-initio calculations. This molecule represents a potentially selective boron carrier in Boron Neutron Cancer Therapy (BNCT) and exhibits amphiphilic characteristics. Its structural and dynamic features were studied comparing NMR data acquired in both aggregating and non-aggregating conditions. Aggregates are characterized by rapid exchange with the bulk and by high sensitivity to temperature conditions. An unusually stable intra-molecular CH^{{radical dot}{radical dot}{radical dot}}O hydrogen bond was found to persist in water solution both for the free molecules and after aggregate formation. At the same time, inter-molecular specific CH^{{radical dot}{radical dot}{radical dot}}O interactions do not seem effective in the aggregate formation process, which appears to take place only on non-specific hydrophobic basis.