- Synthesis of meso-substituted porphyrins carrying carboranes and oligo(ethylene glycol) units for potential applications in boron neutron capture therapy
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Selective delivery of 10B to tumours is one of the major remaining problems in boron neutron capture therapy (BNCT) of cancer. Porphyrins are selectively accumulated in tumours. Thus two series of carborane-carrying porphyrins were constructed, with additional functionality for attachment of uncharged potentially water-solubilising polyethers 3-(1,2-Dicarbaclosododecaboran(12)-1-ylmethoxy)benzaldehyde was prepared by protection of the aldehyde of 3-(prop-2-ynyloxy)benzaldehyde as a dithioacetal, treatment with decaborane(14) and deprotection. Condensation with a 3-nitrophenyldipyrromethane gave a separable mixture of meso-(3-nitrophenyl)-meso-(3-carboranylmethoxyphenyl)porphyrins, resulting from extensive scrambling at the porphyrinogen stage. Similarly, condensation of 3-(1,2-dicarbaclosododecaboran(12)-1-yl)benzaldehyde with this dipyrromethane gave an analogous mixture of meso-(3-nitrophenyl)-meso-(3-carboranylpheneyl)porphyrins. In this second series, the two regioisomeric bis(nitrophenyl)bis(carboranylphenyl)porphyrins could only be distinguished by X-ray crystallography, their NMR spectra being identical. The nitro groups of the mono(nitrophenyl)porphyrins and the bis(nitrophenyl)-porphyrins were reduced to the corresponding amines with tin(II) chloride and the monoamines were coupled with a ω-methoxy poly(ethylene glycol) chloroformate of mean MW 600 to give the MeOPEGylated tricarboranyl porphyrins.
- Frixa, Christophe,Mahon, Mary F.,Thompson, Andrew S.,Threadgill, Michael D.
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p. 306 - 317
(2007/10/03)
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- DNA binding compounds. VII synthesis, characterization and DNA binding capacity of 1,2-dicarba-closo-dodecaborane bibenzimidazoles related to the DNA minor groove binder Hoechst 33258
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A series of bibenzimidazole derivatives based on the known DNA minor groove binder Hoechst 33258 have been prepared to include a 1,2-dicarba-closo-dodecaborane cage for potential use in boron neutron capture therapy (BNCT). The carborane derivatives (5)-(7) were chosen to reduce the steric inhibition of minor groove DNA binding displayed by the previously prepared carborane ligand (4). The synthesis and preliminary DNA binding studies of these bibenzimidazole derivatives are presented herein.
- Bateman, Stuart A.,Kelly, David P.,Martin, Roger F.,White, Jonathan M.
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p. 291 - 301
(2007/10/03)
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- Tumour-targetted Boranes. Part 2. Coupling of closo-Carboranes to Substituted 2-Nitroimidazoles via 1,3-Dipolar Cycloaddition
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Carboranes targetted to specific tumour tissues are important for boron neutron capture therapy of cabcer.Direct syntheses of carboranes linked to 2-nitroimidazole were unsuccesful.A mild procedure for 1,3-dipolar cycloaddition of 4-(carboranylmethoxy)benzonitrile N-oxide 32 with a nitroimidazolyl-alkene 27 and with nitroimidazolyl-alkynes 3 and 30 has been developed, using a series of model reactions, yielding a dihydroisixazole 28 and the isoxazole 29 and 31, respectively.The nitrile oxide 32 is unusually stable.Dithioacetals are shown to be suitable protecting groups for aromatic aldehydes under the vigorous reductive and Lewis acidic-basic conditions of carborane formation. 6-Methoxy-4H-benzopyranoisoxazole 16 has been synthesised by intramolecular 1,3-dipolar cycloaddition.The structure of the isoxasole derivative 29 has been confirmed by an X-ray crystal structure analysis.
- Scobie. Martin,Mahon, Mary F.,Threadgill, Michael D.
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p. 203 - 210
(2007/10/02)
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- Synthesis of Carborane-containing Nitroimidazole Compounds via Mild 1,3-Dipolar Cycloaddition
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Nitroimidazole-linked carboranes are synthesized in good yield from ω-alkenyl- and ω-alkynyl-2-nitroimidazoles and a carborane nitrile oxide by 1,3-dipolar cycloaddition under mild conditions.
- Scobie, Martin,Threadgill, Michael D.
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p. 939 - 941
(2007/10/02)
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