The Case of Silodosin
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Department of Chemistry Doctorate School in Industrial Chemical - XXVII Cycle New processes for the APIs industrial production: the case of silodosin Ph. D. Thesis of Francesco CALOGERO R09773 Tutor: Prof. Daniele Passarella Cotutor: Dr. Emanuele Attolino Coordinator: Prof. Dominique Roberto Academic Year: 2013/2014 Ai miei genitori Dietro ogni problema c’è un’opportunità (Behind every problem there is an opportunity) Galileo Galilei (1564-1642) ABSTRACT This thesis is focused on the development of new synthetic processes for the production of already known Active Pharmaceutical Ingredients (APIs). The research work was performed in the laboratories of Dipharma Francis srl, a company which operates in the generic drug market. The launch of the generic version of a drug in the market often leads to lowering of product prices for both the branded product and the generic ones. For this reason, the process adopted to produce an API has to be innovative, efficient, safe and, of course, cheaper than the existing ones, in order to be competitive in the market. During my Ph.D. I worked on the synthesis of some APIs, in particular here I report the feasibility and development studies of an alternative process to produce silodosin. Silodosin is an API used as a treatment for the symptoms of Benign Prostatic Hyperplasia (BPH). In order to establish the synthetic strategy and to outline our freedom to operate, an accurate survey of the whole patent literature about silodosin has been done. During the feasibility study several synthetic approaches have been tried in order to functionalise indoline at positions 5 and 7. A copper(I) catalysed C-arylation reaction and a regioselective electrophilic aromatic substitution revealed to be the best choices to introduce respectively substituents in position 5 and 7 of indoline. The synthesis continued with a diastereoselective reductive amination which after crystallisation yielded optically pure amine A that is the key intermediate for the synthesis of silodosin and ended converting amine A into Silodosin using already reported procedures. Our new process to prepare silodosin starting from commercially available and cheap indoline consists of 11 steps. The whole synthetic route has been performed in gram scale using only 4 purifications of key intermediates. Silodosin has been finally obtained in a 10% overall yield, with a purity greater than 99% measured by HPLC and an optical purity greater than 99% measured by HPLC on chiral stationary phase. TABLE OF CONTENTS ABSTRACT .......................................................................................................................... 6 LIST OF ABBREVIATION .................................................................................................... 13 PREFACE ............................................................................................................................... 16 DIPHARMA FRANCIS .................................................................................................... 19 GENERICS ..................................................................................................................... 21 INDUSTRIAL PROPERTY ................................................................................................ 27 RESEARCH AND DEVELOPMENT IN INDUSTRY ............................................................ 30 PROCESS R&D CHEMISTRY .......................................................................................... 33 AIM OF THE THESIS ...................................................................................................... 39 SILODOSIN ........................................................................................................................... 40 1 Introduction .................................................................................................................. 42 1.1 Activity and therapeutic information .................................................................... 46 1.2 Silodosin state of art .............................................................................................. 50 1.2.1 Indoline scaffold (Part A): Nucleophilic indoline reagent ............................... 53 1.2.2 Indoline scaffold (part A): Electrophilic indoline reagents ............................. 80 1.2.3 Catechol scaffold (part B) ............................................................................... 83 1.2.4 Polymorphism ................................................................................................. 87 2 Result and Discussion: Feasibility ................................................................................. 90 2.1 FEASIBILITY ............................................................................................................ 92 2.1.1 INVESTIGATION ON POSITION 5 FUNCTIONALISATION ................................. 92 2.1.2 INTRODUCTION OF 7 POSITION SUBSTITUENT ............................................ 124 2.1.3 CONNECTION TO THE FORMAL SYNTHESIS OF SILODOSIN .......................... 154 2 Result and Discussion: Development ......................................................................... 162 2.2 DEVELOPMENT .................................................................................................... 164 2.2.1 COMPOUND 159 ........................................................................................... 166 2.2.2 COMPOUND 76 ............................................................................................. 171 2.2.3 COMPOUND 180 ........................................................................................... 173 2.2.4 COMPOUND 181 ........................................................................................... 175 8 2.2.5 COMPOUND 192 ........................................................................................... 178 2.2.6 COMPOUND 183 ........................................................................................... 180 2.2.7 COMPOUND 186 ........................................................................................... 182 2.2.8 COMPOUND 18 ............................................................................................. 184 2.2.9 COMPOUND 98 ............................................................................................. 186 2.2.10 COMPOUND 68 ........................................................................................... 191 2.2.11 COMPOUND 69 ........................................................................................... 193 2.2.12 COMPOUND 1: silodosin ............................................................................ 196 2.2.13 BRIEF SYNTHESIS OF SILODOSIN ................................................................. 199 3 Conclusion .................................................................................................................. 204 4 Experimental Part ....................................................................................................... 210 Synthesis of compound 3 : .................................................................................... 214 Synthesis of compound 97 : .................................................................................. 216 Synthesis of compound 70 : .................................................................................. 218 Synthesis of compound 72 : .................................................................................. 221 Synthesis of compound 99 : .................................................................................. 223 Synthesis of compound 101 : ................................................................................ 224 Synthesis of compound 102 : ................................................................................ 225 Synthesis of compound 94 : .................................................................................. 226 Formation of Grignard reagent 91 :....................................................................... 227 Synthesis of compound 104 : ................................................................................ 229 Organolithium formation on substrate 104 : ........................................................ 230 Compound 107 : .................................................................................................... 230 Compound 106 : .................................................................................................... 231 Characterisation of side product 110 : .................................................................. 233 Synthesis of compound 114 : ................................................................................ 234 Synthesis of compound 115 : ................................................................................ 235 Synthesis of compound 95 : .................................................................................. 236 Synthesis of compound 116 : ................................................................................ 238 Synthesis of compound 118 : ................................................................................ 239 Compound 120 : .................................................................................................... 241 9 Compound 120-D : ................................................................................................ 241 Synthesis of compound 126 : ................................................................................ 242 Synthesis