Tumour-targetted boranes. Part 3. Synthesis of carbamate-linked nitroimidazolyl carboranes designed for boron neutron capture therapy of cancer

Carboranes targetted to specific tumour tissues are important for boron neutron capture therapy of cancer (BNCT). Carbamoylation of 2-[2-[2-(2-nitroimidazol-1-yl)ethoxy]ethoxy]ethanol 5 and 1-(chloromethyl)-2-(2-nitroimidazol-1-yl)ethanol 6 with carboran-1-yl isocyanate (generated in situ by a Curtius rearrangement of carborane-1-carbonyl azide) gave the corresponding carbamate-linked nitroimidazolylcarboranes 16 and 17. A similar reaction of 4-carboranylphenyl isocyanate with 6 afforded the corresponding carbamate 24.