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ABSTRACT ZOU, YAN. Applications of [2+2+2] Cyclotrimerization

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ABSTRACT ZOU, YAN. Applications of [2+2+2] Cyclotrimerization ABSTRACT ZOU, YAN. Applications of [2+2+2] Cyclotrimerization Reactions and Light-Cleavable Groups in the Generation of Biologically Active Molecules. (Under the direction of Dr. Alexander Deiters). [2+2+2] Cyclotrimerization reactions are a versatile tool for constructing the poly- substituted carbo- and hetero- cyclic ring systems. A number of transition metal catalysts, such as Co, Ru, Rh, Ni and Pd complexes, have been applied. However, there are still regio- and chemo- selectivity issues present in [2+2+2] cyclotrimerization reactions, and only few applications of cyclotrimerization reactions in the synthesis of natural products have been reported. We aimed to develop cyclotrimerization reactions for the assembly of benzene and pyridine core structures found in natural products and for applications in the synthesis of fluorophores. Microwave irradiation, a more recent method used to assist organic reactions, was employed in various cyclotrimerization reactions. In order to obtain greater control over the chemoselectivity of these reactions, we developed a solid-supported method of cyclotrimerization reactions through the immobilization of an alkyne or diyne onto a polymer backbone. This methodology was applied to the assembly of poly-substituted pyridines. Furthermore, the microwave mediated cyclotrimerization methodology was utilized to synthesize various anthracene and azaanthracene fluorophores. Additionally, a cyclotrimerization reaction was used in key steps of the total synthesis of the natural products cryptoacetalide and the pyridine core of cyclothiazomycin. Currently, the cyclotrimerization reaction is being utilized in the ongoing synthesis of petrosasponglide L. Photolabile protecting groups (caging groups) have attracted considerable attention in the field of chemical biology. These caging groups are installed on biomolecules of interest to control their function with light. We applied the photocaging technology towards the development of a caged rapamycin, a biologically relevant natural product. Several caged rapamycin analogs were successfully synthesized and applied in the photo-regulation of enzyme activities. Additionally, a photocaged erythromycin was synthesized and used to control gene expression in E. coli . Carbon-nitrogen (C-N) bond forming coupling reactions play an important role in organic chemistry. A Cu(I)-Re complex was synthesized and successfully used to catalyze C- N coupling reactions. Additionally, a “turn-off” fluorescence switch was developed using [3+2] cycloaddition reactions. Lastly, a set of Coenzyme A analogs were synthesized to study the reaction mechanisms of non-ribosomal peptide synthetases. © Copyright 2012 by Yan Zou All Rights Reserved Applications of [2+2+2] Cyclotrimerization Reactions and Light-Cleavable Groups in the Generation of Biologically Active Molecules by Yan Zou A dissertation submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Chemistry Raleigh, North Carolina 2012 APPROVED BY: _______________________________ ______________________________ Dr. Alexander Deiters Dr. Christian Melander Committee Chair ________________________________ ________________________________ Dr. Joshua G. Pierce Dr. Daniel L. Comins BIOGRAPHY The author, Yan Zou, was born in Liancheng, Fujian Province, P. R. China. Yan attended University of Science and Technology of China (USTC) in 1999, where she got her BS of chemistry degree. Her undergraduate research focused on the transition metal- catalyzed C-N, C-S coupling reaction, under the supervision of Professor Qingxiang Guo. In 2005, Yan moved to the US and studied in Miami Unviersity of Ohio and studied the non-bonding interaction in the physical organic field under the supervision of Professor Benjamin W. Gung. In August of 2006, she got married to Haisheng Lin and decided to transfer to North Carolina. In 2007, she graduated from Miami University of Ohio with a MS in Chemistry degree and moved to North Carolina State University to pursue her Ph.D. study in organic chemistry. Her Ph.D. research was performed under the supervision of Professor Alexander Deiters and covered several fields, including the development and application of cyclotrimerization reactions, the synthesis of caged small molecules and CoA analogs, and transition metal catalyzed C-N coupling. After she got her Ph.D. degree in August of 2012, she began her postdoctoral research at Emory Unviersity. ii ACKNOWLEDGMENTS There are many people I would like to show my gratitude to. First of all, I want to acknowledge my advisor Professor Alexander Deiters for his guidance in my research, the financial support and for always being supportive throughout the five years of my Ph.D. study. His enthusiasm, inspiration, and conscientiousness in science taught me how to be a scientist. I am grateful to all members of Deiters lab. I would especially like to thank Doug, Jesse, Harry, Andrew, Jeane, Colleen, Rajendra, Qingyang, Laura, Jessica, Meryl, Kalyn, Alex, and James for making the lab like a family, for advising and helping me in the lab and my daily life, reading and correcting my manuscripts, prelim document and thesis. I want to thank my collaborators Laura, Jie, Kalyn, the Hahn group (UNC Chapel Hill), the Schmeing group (McGill University), and the Maggard group (NCSU) for their scientific contribution to my work. Additionally, I want to express my gratutide to my committee members, including Dr. Melander, Dr. Comins, Dr. Pierce, Dr. Williams and Dr. Novak, for their help and advices on my research. I would also like to thank the Melander lab, Comins lab, Lindsey lab. Most importantly, I would like to show my deepest gratitude to my family, my Mom, my Dad, and my brothers for their deep love and support throughout my life. I especially want to thank my husband Haisheng for the love and always being on my side, sharing my happiness and sadness. Thank you to all of my friends for making my life in Raleigh more colorful. iii TABLE OF CONTENTS List of Tables ........................................................................................................................ viii List of Figures ......................................................................................................................... ix List of Schemes ...................................................................................................................... xii List of Symboles and Abbreviation ...................................................................................... xix CHAPTER 1: Transition Metal-Catalyzed [2+2+2] Cyclotrimerization Reactions ................ 1 1.1 The [2+2+2] Cyclotrimerization Reaction Approach to Benzene Derivatives .............. 1 1.1.1 Mechanism .............................................................................................................. 1 1.1.2 Regioselectivity of Cyclotrimerization Reactions .................................................. 4 1.2 [2+2+2] Cyclotrimerization Reaction Approach to Pyridine Derivatives ..................... 9 1.3 The Use of Temporary Linkers in [2+2+2] Cyclotrimerization Reactions ................. 16 1.4 Natural Product Synthesis via [2+2+2] Cyclotrimerization Reactions ........................ 18 1.4.1 Benzene-Containing Natural Products .................................................................. 18 1.4.2 Pyridine-Containing Natural Products .................................................................. 27 1.5 Microwave-Assisted Cyclotrimerization Reactions .................................................... 32 1.5.1 Microwave-Assisted Organic Synthesis ............................................................... 32 1.5.2 Microwave-Assisted [2+2+2] Cyclotrimerization Reactions ............................... 36 CHAPTER 2: Pyridines Synthesis via Solid-Supported Cyclotrimerization Reaction ........ 43 2.1 Introduction .................................................................................................................. 43 2.2 Results and Discussion ................................................................................................ 45 2.3 Summary and Outlook ................................................................................................. 50 2.4 Experimental ................................................................................................................ 51 iv CHAPTER 3: Synthesis of Anthracene and Azaanthracene Fluorophores via [2+2+2] Cyclotrimerization Reaction ........................................................................... 58 3.1 Introduction .................................................................................................................. 58 3.2 Results and Discussion ................................................................................................ 59 3.3 Conclusion and Outlook .............................................................................................. 72 3.4 Experimental ................................................................................................................ 72 CHAPTER 4: Total Synthesis of Cryptoacetalide ................................................................. 89 4.1 Introduction .................................................................................................................. 89 4.2 Total Synthesis of Crytoacetalide ................................................................................ 90 4.3
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