Crystallographic report: Synthesis and biological evaluation of novel azanonaboranes as potential agents for boron neutron capture therapy

A number of (hydroxyalkylamine)‐N‐(aminoalkyl)azanonaborane(11) derivatives have been synthesized to provide azanonaboranes with different hydrophilic functional groups for use in the treatment of cancer by boron neutron capture therapy (BNCT). The exo‐diamine group of (aminoalkylamine)‐N‐(aminoalkyl)azanonaborane(11) {H₂N(CH₂)_mH₂NB₈H₁₁NH(CH₂)_mNH₂, where m = 4–6} can be substituted by amino alcohol ligands {HO(CH₂)_nNH₂, where n = 3 and 4} to give azanonaboranes containing free amino and hydroxy groups: (3‐hydroxypropylamine)‐N‐(aminobutyl)azanonaborane(11) {HO(CH₂)₃H₂NB₈H₁₁NH(CH₂)₄NH₂}, 1 ; (4‐hydroxybutylamine)‐N‐ (aminobutyl)azanonaborane(11) {HO(CH₂)₄H₂NB₈H₁₁NH(CH₂)₄NH₂}, 2 ; (3‐hydroxypropylamine)‐N‐ (aminopentyl)azanonaborane(11) {HO(CH₂)₃H₂NB₈H₁₁NH(CH₂)₅NH₂}, 3 ; (4‐hydroxypropylamine)‐N‐(aminopentyl)azanonaborane(11) {HO(CH₂)₄H₂NB₈H₁₁NH(CH₂)₅NH₂}, 4 ; (3‐hydroxypropylamine)‐N‐(aminohexyl)azanonaborane(11) {HO(CH₂)₃H₂NB₈H₁₁NH(CH₂)₆NH₂}, 5 . The in vitro toxicity test using Chinese hamster‐V79 cells showed that compounds 1 – 3 were less toxic (LD₅₀ value of ～2.3, 1.7 and 1.4 mM , respectively) than spermine and spermidine (LD₅₀ value of ～0.88 and 0.66 mM , respectively). In vivo distribution experiments of these compounds in Lewis lung carcinoma and B16 melanoma tumor‐bearing mice showed that boron can be found in tumor tissue. The compounds prepared can be considered as a new class of boron containing polyamine compounds that may be useful for boron neutron capture therapy of tumors. Copyright © 2005 John Wiley & Sons, Ltd.