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A Multidisciplinary Investigation into the Design, Synthesis and Evaluation of a Novel Class of Anti-Glioblastoma Drug Fragments Christopher Sherer A thesis submitted in partial fulfilment for the requirements for the degree of Doctor of Philosophy at the University of Central Lancashire January 2017 STUDENT DECLARATION FORM Concurrent registration for two or more academic awards Either *I declare that while registered as a candidate for the research degree, I have not been a registered candidate or enrolled student for another award of the University or other academic or professional institution Or *I declare that while registered for the research degree, I was with the University’s specific permission, a *registered candidate/*enrolled student for the following award: _____________________________________________________________________________ Material submitted for another award Either *I declare that no material contained in the thesis has been used in any other submission for an academic award and is solely my own work Or *I declare that the following material contained in the thesis formed part of a submission for the award of _____________________________________________________________________________ * delete as appropriate Collaboration Where a candidate’s research programme is part of a collaborative project, the thesis must indicate in addition clearly the candidate’s individual contribution and the extent of the collaboration. Please state below: Signature of Candidate _________________________________________________________ Type of Award Doctor of Philosophy School School of Pharmacy and Biomedical Sciences 2 ABSTRACT Cancer is the second biggest global killer,[1,2] with cancers of the brain and central nervous system accounting for a disproportionately high number of deaths.[3] The most prolific cancer of the central nervous system is glioblastoma, for which prognosis is still very poor. In this project, analogues of two lead compounds with known activity against glioblastoma cell lines (compounds 4 and 5, Figure 1) were produced in order to develop structure-activity relationships and discover compounds with superior activities against glioblastoma. H HO OH N N H 4 H 5 4 5 Figure 1 - The structures of the lead compounds 4 and 5 Analogues of compound 4 were the result of a rigorous similarity search of the ZINC database,[4,5] as well as using chemical intuition to identify potential analogues. A scaffold-hopping approach was undertaken, through which two new compound classes were identified as potentially superior lead compounds for future work (Figure 2). OH HO N N H 168 214 Figure 2 - The structures of two analogues of compound 4 with different scaffolds and superior activity, compounds 168 and 214 Compound 4 is known to induce cell death through the induction of elevated levels of cellular reactive oxygen species (ROS),[6] which may be formed via the radical form of compound 4 and its analogues. The connection between the anticancer activity of 4 and its analogues with the propensity of these compounds to form radicals was also investigated. Enthalpic values relevant to radical formation (BDE, AIP, PDE, PA and ETE) were calculated using a density functional theory (DFT) approach. Although no strong correlation was found for the whole series of compounds, the data indicates that correlations may exist within certain structural classes. The anticancer activity of compound 5, a prodrug, was compared against 11 analogues of both the prodrug and active form of the compound (Scheme 1). It was found that compound 9 has superior activity to that of the prodrug 5. Substitutions at the N-position of 5 were also found 3 to have a significant effect on activity, with an N-tosyl analogue having significantly improved activity against glioblastoma cell lines and short term cultures. The results obtained suggest that future work on this series should therefore be based around compound 9, a subclass of indoles that have wide ranging anticancer activity, but have not yet been reported against glioblastoma. H N OH H N H 5 N H 9 Scheme 1 - The degradation of 5 into its suspected active form (9) In conclusion, analogues were discovered within this project which improved upon the anticancer activity of both compounds 4 and 5. For compound 4, two alternative scaffolds were identified as superior and novel lead compounds against glioblastoma, and there is some indication that there may be a correlation between radical formation and anticancer activity within specific structural classes of this functional class of compounds. For prodrug 5, substituents at the N-positon were found to have a significant effect on activity, and the activity of the active form (9) was found to be superior to the activity of the prodrug. 4 CONTENTS STUDENT DECLARATION FORM .................................................................................................... 2 ABSTRACT ...................................................................................................................................... 3 CONTENTS ..................................................................................................................................... 5 LISTS OF ILLUSTRATIVE MATERIALS ............................................................................................ 12 List of figures ........................................................................................................................... 12 List of schemes ........................................................................................................................ 18 List of tables ............................................................................................................................ 22 List of equations ...................................................................................................................... 24 List of graphs ........................................................................................................................... 26 ACKNOWLEDGEMENTS ............................................................................................................... 27 ABBREVIATIONS, ACRONYMS AND INITIALISMS......................................................................... 28 CHAPTER 1 – INTRODUCTION ..................................................................................................... 33 1.1 Cancer ......................................................................................................................... 34 1.1.1 Glioblastoma ....................................................................................................... 35 1.1.2 The Blood-Brain Barrier ...................................................................................... 37 1.1.3 Chemoresistance ................................................................................................. 38 1.2 Reactive Oxygen Species ............................................................................................. 39 1.2.1 Using ROS to kill cancer cells ............................................................................... 40 1.2.2 Antioxidants ........................................................................................................ 41 1.3 The Lead Compounds .................................................................................................. 43 1.3.1 The Lead Compound 5 ........................................................................................ 44 5 1.3.2 The Lead Compound 4 ........................................................................................ 48 1.4 Project Structure ......................................................................................................... 50 CHAPTER 2 – PROJECT BACKGROUND ........................................................................................ 51 2.1 The Indole Privileged Structure................................................................................... 52 2.2 Indole Syntheses ......................................................................................................... 53 2.2.1 The Fischer Indole Synthesis ............................................................................... 54 2.2.2 Synthesis of Indoles From 2-Alkynyl Anilines ...................................................... 56 2.2.3 Larock Indole Synthesis ....................................................................................... 60 2.2.4 Reductive Cyclisations ......................................................................................... 61 2.2.5 The Bartoli Indole Synthesis ................................................................................ 65 2.2.6 Summary of Indole Syntheses ............................................................................. 66 2.3 Developing Analogues................................................................................................. 68 2.3.1 Chemical Space ................................................................................................... 69 CHAPTER 3 – INTRODUCTION TO QUANTUM CHEMICAL METHODS FOR ENERGETIC CALCULATIONS OF MOLECULAR SPECIES ................................................................................... 78 3.1 Introduction ................................................................................................................ 79 3.2 The Schrödinger Equation ........................................................................................... 79 3.3 The Born-Oppenheimer