Synthesis of Enantiomerically Pure Polyfluorobenzo[D]Sultams

FACOLTÀ DI SCIENZE MATEMATICHE, FISICHE E NATURALI DIPARTIMENTO DI CHIMICA ORGANICA E INDUSTRIALE CORSO DI DOTTORATO DI RICERCA IN CHIMICA INDUSTRIALE - XXI CICLO Chim/06 TESI DI DOTTORATO DI RICERCA Synthesis of enantiomerically pure polyfluorobenzo[d]sultams AARON TAGLIABUE MATR. R06491 Tutor: Prof. Dario Landini Co-Tutor: Dott. Michele Penso Coordinatore: Prof. Paolo Ferruti ANNO ACCADEMICO 2008/2009 Synthesis of polyfluorobenzo[d]sultams 2 Synthesis of polyfluorobenzo[d]sultams 1 INTRODUCTION ............................................................................................. 5 2 SULTAMS ......................................................................................................... 13 2.1 Sultams in medicinal chemistry ................................................................................... 13 2.2 Sultams as chiral auxiliaries .......................................................................................... 22 2.3 Sultams as fluorinating agent ....................................................................................... 31 2.4 Strategies used in sultam synthesis ............................................................................. 35 2.5 Strategies used in benzosultam synthesis .................................................................. 45 3 RESULTS ........................................................................................................... 53 3.1 Synthesis of Benzosultams ............................................................................................ 55 3.2 Stereochemistry of Benzosultams ................................................................................ 85 4 EXPERIMENTAL PART .............................................................................. 101 5 BIBLIOGRAPHY ........................................................................................... 231 3 Synthesis of polyfluorobenzo[d]sultams 4 Synthesis of polyfluorobenzo[d]sultams 1 INTRODUCTION Sulfonamido group, the open-chain analog and the historical “ancestor” of sultams, is a very common organic functional group; in fact it is well known for its wide range of biological activities, holding the prestigious position of being the first synthetic compounds to have had utility in human therapy. Sulfonamide drugs in fact were the first antimicrobial drugs, and paved the way for the antibiotic revolution in medicine. The first sulfonamide synthesized was trade named Prontosil and was discovered by a team under the general direction of Farben executive Heinrich Hoerlein, synthesized by Bayer chemist Josef Klarer and tested under the direction of physician/researcher Gerhard Domagk, who subsequently would have received the 1939 Nobel Prize in Medicine.1 The first official communication about the breakthrough discovery was not published until 1935,2 more than two years after the drug was patented by Klarer and his research partner Fritz Mietzsch. Experiments with Prontosil began in 1932 in the laboratories of Bayer AG, at that time a component of the huge German chemical trust IG Farben and showed that Prontosil was the first medicine ever discovered that could effectively treat a range of bacterial infections inside the body.3,4 It had a strong protective action against infections caused by streptococci, including blood infections, childbed fever, and erysipelas, and a lesser effect on infections caused by other cocci. 5 Synthesis of polyfluorobenzo[d]sultams Few people today would deny that 1936 was the turning point in the history of puerperal infection, one of the most common cause of death during childbirth, and that the arrival of Prontosil brought about the change: obviously when penicillin became available in 1945 the situation became better still, because that antibiotic is an even more potent antistreptoccal agent than the sulfonamides, but it is evident that even if penicillin had not arrived when it did, the story of streptococcal puerperal fever would not have been very different. Graphic 2-1: Decline in puerperal sepsis mortality in England and Wales, 1928–1948. The average figure for the years 1928–30 istaken as 100 and the total for each subsequent year is expressed in terms of that. In 1935 Tréfouël and his colleagues at the Pasteur Institute observed that Prontosil had no effect at all in the test tube, exerting its antibacterial action only in live animals; they soon surprised the scientific world by the suggestion that the red dye was probably a prodrug and that was metabolized into two pieces inside the body, to a much simpler compound, p-aminobenzene sulfonamide. The discovery helped establish the concept of "bioactivation" and dashed the German corporation's dreams of enormous profit; the active sulfanilamide had been known for many years being synthesized in 1906 and was widely used in the dye-making industry; its patent had since expired and the drug was available to anyone. These findings naturally led to a change-over in human therapy from red prontosil to the simpler and cheaper compound which we soon came to know by the name Sulfanilide, the first of the ‘‘sulfa drugs’’. 6 Synthesis of polyfluorobenzo[d]sultams O O O O O S S H N Structural NH 2 HO H2N 2 Metabolization analogy N N NH2 NH2 NH2 PABA Figure 2-1 The important role of sulfonamide is due to its structural analogy to p-Aminobenzoic acid (PABA) which is needed in bacteria organisms for the synthesis of folic acid; they interfere with folate metabolism in the bacterial cell by competitively blocking the biosynthesis of tetrahydrofolate, which acts as a carrier of one-carbon fragments and is necessary for the ultimate synthesis of nucleic bases (most notably thymine, but also purine bases) but also for the synthesis of DNA, RNA and bacterial cell wall proteins. Unlike mammals, bacteria and protozoan parasites usually lack a transport system to take up preformed folic acid from their environment. Most of these organisms must synthesize folates, although some are capable of using exogenous thymidine, circumventing the need for folate metabolism. Thus folate deficiency hinders DNA synthesis and cell division, affecting RNA transcription, and subsequent protein synthesis. Sulfonamides are capable to interfere with the metabolic processes in bacteria that require PABA in particular, having a greater affinity than p- aminobenzoic acid, they compete as a substrate of the enzyme dihydropteroate synthetase in the conversion of dihydropteroate diphosphate in dihydropteroic acid. The result of this discovery was a sulfa craze. For several years in the late 1930s hundreds of manufacturers produced tens of thousands of tons of myriad forms of sulfa. This and nonexistent testing requirements lead to the ELIXIR SULFANILAMIDE DISASTER in the fall of 1937; in the same year S. E. Massengill Co., a pharmaceutical manufacturer, created a preparation of sulfanilamide using diethylene glycol as a solvent, and called the preparation "Elixir Sulfanilamide". Diethylene glycol is poisonous to humans, but the company's chief pharmacist and chemist, was not aware of this, although it was known at the time. At least 100 people were poisoned with diethylene glycol and died and this led to the passage of the Federal Food, Drug, and Cosmetic Act in 1938 but, as the first and only effective antibiotic available in the years before Penicillin, sulfa drugs continued to thrive through the early years of World 7 Synthesis of polyfluorobenzo[d]sultams War II and they are credited with saving the lives of tens of thousands of patients. Sulfa had a central role in preventing wound infections during the war: in fact american soldiers were issued a first aid kit containing sulfa powder and were told to sprinkle it on any open wound. Figure 2-2 Many thousands of molecules containing the sulfanilamide structure have been created since its discovery (by one account, over 5400 permutations by 1945), yielding improved formulations with greater effectiveness and less toxicity. Sulfonamides, however, are not only used as competitive inhibitors of the enzyme dihydropteroate synthetase but they have been in clinical use for over 50 years, because of their antibacterial and antimycotic activity, for example in the treatment of many diseases like: • pneumonia caused by Pneumocystis Carinii , • drug-resistant Malaria and Toxoplasmosis, • some sexually transmitted infections ( Trachoma, Clamydia, Chancroid ), • in inflammatory bowel disease, • for respiratory infections for special problems (e.g. infection with Nocardia ), • for acute urinary tract infection • for infected burns. Moreover these molecules are still widely used for conditions such as acne and urinary tract infections, and are receiving renewed interest for the treatment of infections caused by bacteria resistant to other antibiotics. Unsaturated sulfonamides were also identified as potent, and irreversible inhibitors of cysteine proteases 5, which are essential to the life cycles of many pathogenic protozoa; preliminary 8 Synthesis of polyfluorobenzo[d]sultams biological evaluation of some of this molecules has shown a promising pharmacological activity; this kind of structures have been studied even in relation with their ability to inhibit a series of matrix metalloproteinases, particularly gelatinase A, collagenase-3, and stromelysin-1 and for the treatment of multiple sclerosis, artherosclerotic plaque rupture, aortic aneurysm, heart failure, left ventricular dilation, restenosis, periodontal disease, or other autoimmune or inflammatory disorders

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