Deoxyvariolins and polymer therapeutics

Abstract

Polymeric carrier molecules have been shown to improve the pharmacokinetics and pharmacological profile of small-molecule anticancer drugs. The variolins are a group of marine natural product-derived cytotoxins whose clinical efficacy may be improved through conjugation with a polymer backbone. This thesis first describes the optimisation of a synthesis of the non-natural analogue deoxyvariolin B, a synthesis that was devised by Anderson and Morris immediately prior to the commencement of this project. The synthesis, comprised of six linear steps, was refined to give an overall yield of 25%. As part of a much larger structure-activity relationship investigation being carried out by Pharma Mar, SA (a Spanish pharmaceutical company specialising in marine natural products), a small library of deoxyvariolin analogues, numbering approximately fifteen, was also synthesised and tested in vitro against the P388 murine leukaemia cell line. All analogues synthesised showed an appreciable loss of bioactivity (typically around an order of magnitutude) compared to that of deoxyvariolin B, Attempts at acylating deoxyvariolin B with the tetrapeptide biolinker were hampered by DVB's awkward reactivity and the low stability of some of the products. A more suitable deoxyvariolin analogue, in terms of its bioactivity as well as chemical reactivity, was therefore chosen for development into a polymer therapeutic. This analogue was successfully conjugated with a tetrapeptide biolinker to give a compararably bioactive conjugate that was to be reacted with an activated polymer backbone. The final part of this thesis, however, describes work that was carried out with the polymeric starting material, in which it was revealed that two unforeseen side reactions were taking place. These side reactions ultimately precluded the synthesis of the target constructs.