Dissertation zur Erlangung des Doktorgrades der Fakultät für Chemie und Pharmazie der Ludwig-Maximilians-Universität München Total Synthesis of Wickerol A – Development of a Photoswitchable AMPA Receptor Antagonist von Shu-An Liu aus Villach, Österreich 2017 Erklärung Diese Dissertation wurde im Sinne von § 7 der Promotionsordnung vom 28.November 2011 von Herrn Prof. Dr. Dirk Trauner betreut. Eidesstattliche Versicherung Diese Dissertation wurde eigenständig und ohne unerlaubte Hilfe erarbeitet. München, ..................................... ............................................................................. Shu-An Liu Dissertation eingereicht am 08. Juni 2017 1. Gutachter: Prof. Dr. Dirk Trauner 2. Gutachter: Dr. Dorian Didier Mündliche Prüfung am 17.07.2017 For my family. 謹以此文獻給我的家庭. Parts of this thesis have been published in peer-reviewed journals: “Synthesis of the Antiviral Diterpene Wickerol A”, S.-A. Liu, D. Trauner, J. Am. Chem. Soc., 2017 , ASAP. “Optical control of AMPA receptors using a photoswitchable quinoxaline-2,3-dione antagonist”, D. M. Barber, † S.-A. Liu,† K. Gottschling, M. Sumser, M. Hollmann, D. Trauner, Chem. Sci. 2017 , 8, 611- 615. † These authors contributed equally to this work. Parts of this thesis have been presented at a scientific conference: 16th Tetrahedron Symposium: Challenges in Bioorganic & Organic Chemistry Poster presentation: “Light Controlled Antagonists of AMPA Receptors“. Berlin, Germany, June 2015 I Abstract Part I: Terpenes represent the largest family of natural products and comprise compounds with extremely diverse biological and physical properties. One unique member of this class is wickerol A, an antiviral diterpene isolated from the fungus Trichoderma atroviride FKI-3849. It features an unprecedented and highly congested carbon framework with seven stereocenters, of which two are quaternary carbons. Out of several failed approaches to wickerol A evolved a route which ultimately led to its first total synthesis. The highly convergent strategy is based on a Diels–Alder reaction and an intramolecular alkylation to complete the 6-5-6-6 ring system. TBSO OTBS OMs Me Diels Alder O Me Me O reaction O + H H H OTBS OTBS OMOM intramolecular O alkylation OMOM OH wickerol A Part II: AMPA receptors are a subclass of ionotropic glutamate receptors which play a crucial role in excitatory neurotransmission. They are also involved in processes such as memory and learning as well as several psychiatric disorders. In the second part of this thesis, we present the development of the first photoswitchable antagonist that is selective for AMPA receptors. Our light-responsive ligand, ShuBQX-3, blocks the receptor in its dark-adapted trans -isomer and can be switched to its significantly less active cis -isomer using blue light. Control of action potential firing in hippocampal CA1 neurons could be demonstrated with ShuBQX-3. In addition, it exhibits a remarkable red-shifting of its photoswitching properties through interactions with the AMPA receptor ligand binding site. II III Acknowledgement This PhD has certainly been the most challenging endeavor of my life so far. When I embarked on it four years ago, I had no idea how difficult it would be but I´d like to think that all the hardship was worth it, that I learned a lot and that I have become a better person through it. This journey was shaped by many people, some of which I´d like to thank here: I want to express my gratitude to Prof. Dr. Dirk Trauner for giving me the opportunity to work in his group and to the permanent staff: Heike Traub, Alexandra Grilic, Dr. Martin Sumser, Carrie Louis, Luis de la Osa de la Rosa and Mariia Palchyk. I would also like to thank Dr. Dorian Didier, Dr. Thomas Magauer, Prof. Dr. Franz Bracher and Prof. Dr. Manfred Heuschmann for being part of my defense committee and the Studienstiftung des deutschen Volkes for financial support. My gratitude also goes to Dr. David Barber and Dr. Martin Sumser, who worked with me on the ShuBQX-3 project, as well as Dr. Guillaume Journot and Dr. Bryan Matsuura, who helped me with the total synthesis of wickerol A. I also want to thank all my interns: Alexander Harjung, Jens Popp, Julius Hillenbrand, Peter Gänsheimer and Simon Graßl. Furthermore, I am grateful to the analytical department of the LMU Munich: Claudia Dubler, Dr. David Stephenson, Dr. Werner Spahl, Sonja Kosak and particularly Dr. Peter Mayer. I am very thankful to all the past and present members of the Trauner and Magauer group who have generated a great working environment, especially to Dr. Martin Olbrich (for his humor), Dr. David Barber (for all the great coffee breaks and proofreading so many documents), Dr. Cedric Hugelshofer (for his early morning visits), Dr. Robin Meier (for always having encouraging words), Matthias Schmid (for his cheerfulness) and Dr. Hong-Dong Hao (for his calmness and helpful discussions). In addition, I want to thank Dr. Guillaume Journot, Dr. Nicolas Armanino and Dr. Bryan Matsuura for having been awesome hood mates who patiently dealt with all my craziness. I am especially grateful to Dr. Giulio Volpin, Antonio Rizzo and Dr. Julius Reyes for their friendship and support: without you I would have been lost. IV I can also call myself lucky to have enjoyed the friendship of Edris Parsa, Jürgen Vorndran and especially Julia Kress, who always tried to get me out of the lab and show me new things. Last but not least, I want to thank my parents and my sister for all their support and their sacrifices. Without them, this journey would not have been possible. V List of Abbreviations Å angstrom DMAP 4-(dimethylamino)pyridine Ac acetyl DMAPP dimethylallyl pyrophosphate acac acetylacetone DMDO dimethyldioxirane AIBN azobisisobutyronitrile DME 1,2-dimethyoxyethane AMPA 2-amino-3-(5-methyl-3- DMF dimethylformamide hydroxyisoxazol-4- DMP Dess–Martin periodinane yl)propanoic acid DMSO dimethylsulfoxide aqu aqueous DNA deoxyribonucleic acid ATP adenosine triphosphate d.r. diastereomeric ratio ATR attenuated total reflection E opposite, trans Bn benzyl EDG electron donating group br broad (NMR spectroscopy, IR ee enantiomeric excess spectroscopy) Bu butyl EI electron impact ionization °C degree Celsius ent enantiomer cal calorie(s) enz enzyme CAN ceric ammonium nitrate epi epimer CCDC Cambridge Crystallographic eq equivalent(s) Data Centre ESI electron spray ionization CNS central nervous system (mass spectrometry) CoA coenzyme A Et ethyl COSY homonuclear correlation EWG electron withdrawing group spectroscopy FDA Food and Drug Cp cyclopentadienyl Administration CTP cytidine triphosphate FPP farnesyl diphosphate δ chemical shift (NMR) g gram(s) d doublet (NMR spectroscopy) GABA γ-aminobutyric acid gem germinal D dexter (“right”) D Debye GG geranylgeranyl d day(s) GluR glutamate receptor DBU 1,8-diazabicyclo[5.4.0]undec- GPP geranyl diphosphate 7-ene h hour(s) DCE 1,2-dichloroethane HG II Hoveyda-Grubbs II catalyst DCM dichloromethane HMDS hexamethyldisilazide DIBAL-H diisobutylaluminium hydride HMPA hexamethylphosphoramide DIPA diisopropylamine h·ν irradiation DIPEA diisopropylethylamine HSQC heteronuclear single DIPT diisopropyl d-tartrate quantum coherence Hz Hertz (frequency) VI i iso (mer) NMDA N-methyl-d-aspartate IC 50 half maximal inhibitory NMO N-methylmorpholine-N-oxide concentration NMP 1-methyl-2-pyrrolidinone imid imidazole NMR nuclear magnetic resonance IPP isopentenyl pyrophosphate NOESY nuclear Overhauser effect IR infrared correlation spectroscopy IUPAC International Union of Pure Nu nucleophile and Applied Chemistry p para (isomer) J coupling constant (NMR) PG protecting group k kilo PIDA phenyliodonium diacetate L liter(s) Piv pivaloyl L laevus (“left”) Ph phenyl LBD ligand binding domaine PMB para -methoxybenzyl ether LDA lithium diisopropylamide PP pyrophosphate LG leaving group ppm parts per million LHMDS lithium hexamethyldisilazide PPTS pyridinium para -toluene- M molar sulfonate m meter(s) p-TsOH para -toluenesulfonic acid m medium (IR spectroscopy) pyr pyridine m multiplet (NMR q quartet (NMR spectroscopy) spectroscopy) R undefined substituent m meta rac racemic MABR methylaluminum bis(4- RCM ring closing metathesis bromo -2,6-di-t- R retardation factor butylphenoxide f m-CPBA meta -chloroperbenzoic acid r.t. room temperature Me methyl s strong (IR spectroscopy) MEP methylerythritol phosphate s singlet (NMR spectroscopy) min minute(s) SAR structure activity relationship mL milliliter(s) sat saturated mmol millimole(s) SN nucleophilic substitution MOM methoxymethyl T temperature MS mass spectrometry t time MS molecular sieves t tertiary Ms methanesulfonyl t triplet (NMR spectroscopy) MVA mevalonate TBAF tetrabutylammonium fluoride NADPH nicotinamide adenine TBAI tetrabutylammonium iodide dinucleotide phosphate hydrogen TBDPS tert -butyldiphenylsilyl NBS N-iodosuccinimide TBHP tert -butyl hydrogenperoxide NHC N-heterocyclic carbene TBS tert-butyldimethylsilyl NIS N-iodosuccinimide TES triethylsilyl VII Tf trifluoromethanesulfonyl TFA trifluoroacetic acid THF tetrahydrofurane TIPS triisopropyl TLC thin layer chromatography TMS trimethylsilyl TPP thiamine pyrophosphate TRPV ransient receptor potential channels vanilloid Ts tosyl TTMSS tris(trimethylsilyl)silane tol toluene UV ultraviolet (irradiation) w weak (IR spectroscopy) wt% weight percent Z zusammen, “together” VIII Table of Content Abstract ............................................................................................................................ I Acknowledgement .........................................................................................................