Synthesis and characterization of a novel functionalized azanonaborane cluster for boron neutron capture therapy

Abstract

The reactivity of an azanonaborane cluster containing free amino groups {H₂N(CH₂)₄H₂NB₈H₁₁NH(CH₂)₄NH₂} towards ketones and aldehydes is investigated. In a one step reaction, the reductive amination of some ketones and aldehydes (namely acetone, benzaldehyde, 3-hydroxybenzaldehyde, 4-hydroxybenzaldehyde, 4-nitrobenzaldehyde, 4-acetoxybenzaldehyde, and 4-acetamidobenzaldehyde) with an azanonaborane cluster in the presence of H₃BNH₂(CH₂)₄NH₂ gives monoalkylamino derivatives of the azanonaborane cluster {RHN(CH₂)₄H₂NB₈H₁₁NH(CH₂)₄NHR} where (R = (Me)₂CH–, C₆H₅CH₂–, 3-OHC₆H₄CH₂–, 4-OHC₆H₄CH₂–, 4-NO₂C₆H₄CH₂–, 4-MeOCOC₆H₄CH₂–, or 4-NH₂COC₆H₄CH₂-). The functionalized derivatives of the {B₈N} cluster can be used in boron neutron capture therapy for tumors (BNCT). Similarly, the reductive amination of 5-(4′-formylphenyl)-10,15,20-triphenylporphyrin with the {B₈N} cluster gave a porphyrin bearing azanonaborane cluster, while a porphyrin dimer linked by an azanonaborane moiety was obtained following the same method, starting with a 2 : 1 molar ratio of porphyrin : {B₈N} cluster. 5,10,15,20-Tetraformylphenylporphyrin gave the chance to increase the percentage of boron in the resulting boronated porphyrin, which is considered an important factor for a BNCT delivery agent. With these compounds, the cell toxicity using V79 cells was carried out to determine whether these compounds would have favorable biological properties.