From ortho-carbaborane-9-thiol towards new building blocks

The potential of 1,2-dicarba-closo-dodecaborane(12)-9-thiol, 9-HS-1,2-closo-C2B10H11, for the design of novel building blocks is highlighted by two examples envisioned for incorporation into tumor-selective peptides for boron neutron capture therapy (BNCT). By employing a t-Bu protection strategy the synthesis of a bis-galactosyl-substituted ortho-carbaborane carboxylic acid was elaborated, and the procedure is suggested as a general approach towards carbaboranes with three substituents. Furthermore, a simple route to a tris(ortho-carbaborane) building block starting from pentaerythritol is illustrated. All compounds were synthesized in moderate to high yields and identified by 1H, 11B, and 13C NMR spectroscopy, IR spectroscopy, mass spectrometry, and in one case by X-ray crystallography.

Graphical abstractThe potential of 1,2-dicarba-closo-dodecaborane(12)-9-thiol, 9-HS-1,2-closo-C2B10H11, in the construction of novel building blocks for incorporation into tumor-selective peptides for boron neutron capture therapy (BNCT) is demonstrated at two examples.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► ortho-Carbaborane-9-thiol is applied in the rational design of new building blocks. ► Synthesis of a bis-galactosylated and a tris-carbaboranyl building block. ► Potential building blocks for incorporation into tumor-selective peptides for BNCT.