A study of cellular polyamine uptake and cytotoxicity
thesisposted on 15.12.2014, 10:35 by Benjamin Martin
The synthesis and study of a series of methylated polyamine-fluorophore conjugates is described in this thesis. The conjugates are related by the degree of N-methylation at the N1 and N8 positions of the spermidine backbone, to which is also attached the fluorescent group (MANT) via a short linker at the N4-position. The conjugates were designed in order to exploit the cellular uptake of polyamines and the confirmed affinity of polyamines for DNA. The N-methylation steps in the synthesis of the three conjugates were facilitated by the regioselective introduction of DPP protecting groups at N1 and N8. The controlled degree of methylation was achieved by a step-wise strategy whereby part-methylated substrates featured in the next round of methylation. In this way, the bis-secondary, bis-tertiary and bis-quaternary methylated polyamines could be isolated without the formation of part-methylated products. The inability of BOC protecting groups to facilitate methylation was demonstrated by the direct comparison of BOC and DPP protected substrates throughout the stages of methylation.;The preparation of methylated analogues of spermine is also described in this thesis. Three bis-methylated analogues were prepared, which are related by the degree of methylation of N1,N12. Synthesis of the analogues was via a divergent scheme which approaches the N-derivatisation of polyamines by a fragment strategy. In this way the flexibility to prepare a range of symmetrically substituted N,N bis-alkylated polyamine analogues is provided for future studies. The preparations of this thesis featured the divergent bis-amination of a bis-reactive intermediate by the series of commercially available monoamines: methylamine, dimethylamine and trimethylamine. The three analogues were tested for cytotoxicity using two independent assays, but showed no cytotoxic activity in A549 cells.