Synthesis and in vitro anti-tumor activity of carboranyl levodopa.

Reactions of closo-1-Me-2-Iodobutyl-1,2-closo-dicarborane, 1-Me-2-I(CH₂)₄-C₂B₁₀H₁₀, with l-dopa methyl ester can produce carboranyl l-dopa methyl esters in 54% yield in the presence of sodium hydroxide. The appended closo-carboranes can be decapitated with sodium hydroxide in a mixed solvent of ethanol and deionized water to produce highly water-soluble carboranyl levodopa in 64% yield. All the new compounds were characterized by ¹H, ¹³C, ¹¹B NMR, FT-IR spectroscopy and elemental analysis. The highly water soluble carboranyl levodopa 4 shows promising efficacy of anti-tumors in vitro in the presence of slow neutron beams.