Synthesis of [closo-B12(OH)11NH3]−: A New Heterobifunctional Dodecaborane Scaffold for Drug Delivery Applications

Effective utilization of [closo-B12H12]2– derivatives in targeted drug delivery applications depends upon an efficient strategy to differentiate at least one of the 12 vertices on the B122– core. Precursor molecules must also be able to withstand the initial harsh hydrogen peroxide treatment necessary for hydroxylation of the B–H vertices. We report here a method for preparation of the ammonio derivative [closo-B12(OH)11NH3]− and also demonstrate its utility in construction of a targeted drug delivery scaffold. Treatment of the precursor [closo-B12H11NH3]− with hydrogen peroxide gives the corresponding nitro derivative [closo-B12(OH)11NO2]2– in good yield. The nitro group is easily reduced with hydrogen over a Raney nickel catalyst to produce [closo-B12(OH)11NH3]−. The 11 hydroxyl groups can then be readily converted to carbonates or carbamates. As a proof-of-principle of its utility as a drug delivery system, we used the resulting vertex-differentiated ammonio derivative to construct a platinated pro-dru...