Synthesis and functionalization of nitrosyl rhenacarboranes towards their use as drug delivery vehicles

Abstract The compound has been synthesized and used as precursor to several nitrosyl rhenacarborane complexes with boron-bound B–O(CH 2 ) 2 O(CH 2 ) 2 ‒ tethers to halo, amino and hydroxo functional groups. The last two in particular have afforded a pair of rhenacarborane derivatives, [3,3-(CO) 2 -3-NO- closo -Re(8-O(CH 2 ) 2 O(CH 2 ) 2 NH 3 -3,1,2-C 2 B 9 H 10 )]BF 4 and [3,3-(CO) 2 -3-NO- closo -Re(8-O(CH 2 ) 2 O(CH 2 ) 2 OH-3,1,2-C 2 B 9 H 10 )], for potential use as drug-delivery vehicles. Bioconjugates tethering our delivery vehicles to amino acids or small peptides that are not readily transported across the blood–brain barrier, either by means of membrane-based transport mechanisms or through passive diffusion, could make potential pharmacological agents for central nervous system infiltration. The final nitrosyl complexes are made following nucleophilic ring opening of the β -boron-bound 1,4-dioxane moiety and our work has established that even with unprotected hydroxo and amino terminal groups, the metal can be selectively nitrosylated using [NO][BF 4 ] without destroying the integrity of the B–O(CH 2 ) 2 O(CH 2 ) 2 X (X = OH, NH 3 ) tether.