Utility of boron clusters for drug design. Hansch-fujita hydrophobic parameters pi of dicarba-closo-dodecaboranyl groups.

The spherical boron clusters, dicarba-closo-dodecaboranes (carboranes) are new hydrophobic pharmacophores, which interact hydrophobically with receptors. We have experimentally measured the partition coefficients log P for carboranylphenols employing an HPLC method, and determined the Hansch-Fujita hydrophobic parameters pi of various carboranyl groups. The values (pi=2.69-4.44) vary depending on the position of substitution on the carborane cage and the isomeric form (o-, m-, p-carboranes). These values lie within the range of those of hydrocarbons.