Synthesis of polyamine-nucleotide conjugates as models for drug delivery

This thesis presents new synthetic methods for the synthesis of a range of novel polyamine- nucleotide conjugates, that vary in the nucleotide, the overall charge and the structure of the polyamine moiety. The synthesis of a novel fluorescent bis-benzyl-spermidine-MANT derivative is also described. Synthetic methods were developed to synthesise a range of novel polyamine-thymidine-5'- phosphate and polyamine-ethenoadenosine-5'-phosphate conjugates that will enable an investigation into whether the lack of membrane permeability to di-anionic nucleoside-5'- phosphates can be overcome by the tethering of nucleotides to polyamines. The synthesis of a second set of derivatives, polyamine-nucleoside-5'-diphenyl phosphate conjugates, has produced a range of control compounds in which the charge on the 5'-phosphate is masked. A comparison between the two sets of compounds, the polyamine-nucleoside-5'-phosphate conjugates and the polyamine-nucleoside-5'-diphenyl phosphate conjugates will allow the effect of net overall charge on cellular uptake to be evaluated. Synthetic procedures were also devised for the conjugation of nucleoside-5'-phosphates and nucleoside-5'-diphenyl phosphates to spermidine on each of the three nitrogens (N1, N4 and N8) to provide further evidence for the most favourable position on spermidine to which cytotoxic drugs should be tethered. 1 & The synthesis of a novel N , N -bis-benzyl-spermidine-MANT conjugate has been carried out to investigate the uptake of such a molecule by the polyamine transport system and to look at the intracellular localisation. Confocal laser scanning microscopy images (CLSM) provided evidence that the bis-benzyl-spermidine-MANT conjugate and its parent conjugate are located in both the cytoplasm and the nucleus. The CLSM images show that the bis-benzyl- spermidine-MANT conjugate appears in a higher concentration in the nucleus than in the cytoplasm. Therefore, the conjugate shows good potential as a high affinity carrier to which DNA-targeted cytotoxic drugs could be linked.