Design and Synthesis of Enzyme Inhibitors Against Infectious Diseases : Targeting Hepatitis C Virus NS3 Protease and Mycobacterium tuberculosis Ribonucleotide Reductase

Infectious diseases, including hepatitis C and tuberculosis, claim the lives of over 15 million people each year. Hepatitis C is caused by the hepatitis C virus (HCV) which infects the liver and can ultimately result in liver transplantation. HCV is very adaptive as a result of its high mutation rate. Thus, there is a potential high risk for the development of drug resistance and also a possible cross-resistance due to a structural similarity between many of the HCV NS3 protease inhibitors currently in clinical trial and on the market, that all are based on a P2-proline or a proline mimic. Thus, part of the research behind this thesis was to explore a new structural P3-P2 unit for the NS3 protease inhibitors, a 2(1H)-pyrazinone moiety. A microwave-assisted protocol was developed, and the 2(1H)-pyrazinone core was synthesized in only 2 × 10 min. A series of optimization steps resulted in several submicromolar 2(1H)-pyrazinone-containing NS3 protease inhibitors that performed well against drug-resistant NS3 protease variants. The key modifications were: exchanging the unstable carbamate P3 capping group for a stable urea functionality, transferring the P2 group from the amino acid residue to the pyrazinone ring and elongating the substituent, and using an aromatic acyl sulfonamide in the P1-P1' position. The causative agent of tuberculosis is Mycobacterium tuberculosis (Mtb), which currently infects one third of the world's population. No new TB drugs have been approved in nearly 50 years and drug resistance has been observed for all of the current first-line drugs. Because of the importance of identifying novel drug targets, the ribonucleotide reductase (RNR) enzyme was investigated. The RNR enzyme consists of two R1 and two R2 subunits and is essential for Mtb replication. Starting from hits identified in a virtual screening program, a small library of low molecular weight inhibitors of the association between the R1 and R2 subunits was designed and synthesized. The compounds with the strongest affinity for the R1 subunit of RNR were further evaluated in an orthogonal activity assay. Two RNR inhibitors with promising antimycobacterial effects were identified, which can serve as leads in the further optimization of this class of compounds

Design and Synthesis of Enzyme Inhibitors Against Infectious Diseases : Targeting Hepatitis C Virus NS3 Protease and Mycobacterium tuberculosis Ribonucleotide Reductase

Infectious diseases, including hepatitis C and tuberculosis, claim the lives of over 15 million people each year. Hepatitis C is caused by the hepatitis C virus (HCV) which infects the liver and can ultimately result in liver transplantation. HCV is very adaptive as a result of its high mutation rate. Thus, there is a potential high risk for the development of drug resistance and also a possible cross-resistance due to a structural similarity between many of the HCV NS3 protease inhibitors currently in clinical trial and on the market, that all are based on a P2-proline or a proline mimic. Thus, part of the research behind this thesis was to explore a new structural P3-P2 unit for the NS3 protease inhibitors, a 2(1H)-pyrazinone moiety. A microwave-assisted protocol was developed, and the 2(1H)-pyrazinone core was synthesized in only 2 × 10 min. A series of optimization steps resulted in several submicromolar 2(1H)-pyrazinone-containing NS3 protease inhibitors that performed well against drug-resistant NS3 protease variants. The key modifications were: exchanging the unstable carbamate P3 capping group for a stable urea functionality, transferring the P2 group from the amino acid residue to the pyrazinone ring and elongating the substituent, and using an aromatic acyl sulfonamide in the P1-P1' position. The causative agent of tuberculosis is Mycobacterium tuberculosis (Mtb), which currently infects one third of the world's population. No new TB drugs have been approved in nearly 50 years and drug resistance has been observed for all of the current first-line drugs. Because of the importance of identifying novel drug targets, the ribonucleotide reductase (RNR) enzyme was investigated. The RNR enzyme consists of two R1 and two R2 subunits and is essential for Mtb replication. Starting from hits identified in a virtual screening program, a small library of low molecular weight inhibitors of the association between the R1 and R2 subunits was designed and synthesized. The compounds with the strongest affinity for the R1 subunit of RNR were further evaluated in an orthogonal activity assay. Two RNR inhibitors with promising antimycobacterial effects were identified, which can serve as leads in the further optimization of this class of compounds

Design and Synthesis of Enzyme Inhibitors Against Infectious Diseases : Targeting Hepatitis C Virus NS3 Protease and Mycobacterium tuberculosis Ribonucleotide Reductase

Infectious diseases, including hepatitis C and tuberculosis, claim the lives of over 15 million people each year. Hepatitis C is caused by the hepatitis C virus (HCV) which infects the liver and can ultimately result in liver transplantation. HCV is very adaptive as a result of its high mutation rate. Thus, there is a potential high risk for the development of drug resistance and also a possible cross-resistance due to a structural similarity between many of the HCV NS3 protease inhibitors currently in clinical trial and on the market, that all are based on a P2-proline or a proline mimic. Thus, part of the research behind this thesis was to explore a new structural P3-P2 unit for the NS3 protease inhibitors, a 2(1H)-pyrazinone moiety. A microwave-assisted protocol was developed, and the 2(1H)-pyrazinone core was synthesized in only 2 × 10 min. A series of optimization steps resulted in several submicromolar 2(1H)-pyrazinone-containing NS3 protease inhibitors that performed well against drug-resistant NS3 protease variants. The key modifications were: exchanging the unstable carbamate P3 capping group for a stable urea functionality, transferring the P2 group from the amino acid residue to the pyrazinone ring and elongating the substituent, and using an aromatic acyl sulfonamide in the P1-P1' position. The causative agent of tuberculosis is Mycobacterium tuberculosis (Mtb), which currently infects one third of the world's population. No new TB drugs have been approved in nearly 50 years and drug resistance has been observed for all of the current first-line drugs. Because of the importance of identifying novel drug targets, the ribonucleotide reductase (RNR) enzyme was investigated. The RNR enzyme consists of two R1 and two R2 subunits and is essential for Mtb replication. Starting from hits identified in a virtual screening program, a small library of low molecular weight inhibitors of the association between the R1 and R2 subunits was designed and synthesized. The compounds with the strongest affinity for the R1 subunit of RNR were further evaluated in an orthogonal activity assay. Two RNR inhibitors with promising antimycobacterial effects were identified, which can serve as leads in the further optimization of this class of compounds

Diastereoselective Synthesis of N-Methylspiroindolines by Intramolecular Mizoroki–Heck Annulations

Spiroindolines represent a privileged structure in medicinal chemistry, although stereocontrol around the spirocarbon can be a synthetic challenge. Here we present a palladium(0)-catalyzed intramolecular Mizoroki–Heck annulation reaction from (+)-Vince lactam-derived cyclopentenyl-tethered 2-bromo-N-methylanilines for the formation of N-methylspiroindolines. A series of 14 N-methylspiroindolines were synthesized in 59–81% yield with diastereoselectivity >98%, which was rationalized by density functional theory calculations and confirmed through X-ray crystallography. One spiroindoline was converted to an N- and C-terminal protected rigidified unnatural amino acid, which could be orthogonally deprotected

2-Alkyl substituted benzimidazoles as a new class of selective AT2 receptor ligands

Ligands comprising a benzimidazole rather than the imidazole ring that is common in AT2R ligands e.g. in the AT2R agonist C21, can provide both high affinity and receptor selectivity. In particular, compounds encompassing benzimidazoles, substituted in the 2-position with small bulky groups such as an isopropyl (Ki = 4.0 nM) or a tert-butyl (Ki = 5.3 nM) or alternatively a thiazole heterocycle (Ki = 5.1 nM) demonstrate high affinity and AT2R selectivity. An n-butyl chain, as found in the AT1R selective sartans, makes the ligand less receptor selective. The isobutyl group on the biaryl scaffold present in most AT2R selective ligands reported so far was originally derived from the nonselective potent AT1R/AT2R ligand L-162,313. Notably, in all ligands discussed herein, the isobutyl group was substituted by an n-propyl group and ligands with high affinity to AT2R were provided and in addition the majority of them demonstrate a favorable AT2R/AT1R selectivity. The introduction of fluoro atoms in various positions had no pronounced effect on the affinity data. Ligands with a thiazole or a tert-butyl group attached to the 2-position and with a terminal trifluoromethyl butoxycarbonyl sidechain exhibited a similar stability as C21 in human liver microsomes, while other ligands examined were less stable in the microsome assay.De två första författarna delar förstaförfattarskapet</p

A Series of Analogues to the AT2R Prototype Antagonist C38 Allow Fine Tuning of the Previously Reported Antagonist Binding Mode

We here report on our continued studies of ligands binding tothe promising drug target angiotensin II type 2 receptor (AT2R). Two series of compounds were synthesized and investigated. The first series explored the effects of adding small substituents to the phenyl ring of the known selective nonpeptide AT2R antagonist C38, generating small but significant shifts in AT2R affinity. One compound in the first series was equipotent to C38 and showed similar kinetic solubility, and stability in both human and mouse liver microsomes. The second series was comprised of new bicyclic derivatives, amongst which one ligand exhibited a five-fold improved affinity to AT2R ascompared to C38. The majority of the compounds in the second series, including the most potent ligand, were inferior to C38 with regard to stability in both human and mouse microsomes. In contrast to our previously reported findings, ligands with shorter carbamate alkyl chains only demonstrated slightly improved stability in microsomes. Based on data presented herein, a more adequate, tentative model of the binding modes of ligand analogues to the prototype AT2R antagonist C38 is proposed, as deduced from docking redefined by molecular dynamic simulations

Direct Palladium(II)-Catalyzed Synthesis of Arylamidines from Aryltrifluoroborates

A fast and convenient synthesis of arylamidines starting from readily available potassium aryltrifluoroborates and cyanamides is reported. The coupling was achieved by Pd(II)-catalysis in a one step 20 min microwave protocol using Pd(O₂CCF₃), 6-methyl-2,2′-bipyridyl, TFA, and MeOH, providing the corresponding arylamidines in moderate to excellent yields

Hydrogen Peroxide Induced Toxicity Is Reversed by the Macrocyclic IRAP-Inhibitor HA08 in Primary Hippocampal Cell Cultures

Angiotensin IV (Ang IV), a metabolite of Angiotensin II, is a bioactive hexapeptide that inhibits the insulin-regulated aminopeptidase (IRAP). This transmembrane zinc metallopeptidase with many biological functions has in recent years emerged as a new pharmacological target. IRAP is expressed in a variety of tissues and can be found in high density in the hippocampus and neocortex, brain regions associated with cognition. Ang IV is known to improve memory tasks in experimental animals. One of the most potent IRAP inhibitors known today is the macrocyclic compound HA08 that is significantly more stable than the endogenous Ang IV. HA08 combines structural elements from Ang IV and the physiological substrates oxytocin and vasopressin, and binds to the catalytic site of IRAP. In the present study we evaluate whether HA08 can restore cell viability in rat primary cells submitted to hydrogen peroxide damage. After damaging the cells with hydrogen peroxide and subsequently treating them with HA08, the conceivable restoring effects of the IRAP inhibitor were assessed. The cellular viability was determined by measuring mitochondrial activity and lactate dehydrogenase (LDH) release. The mitochondrial activity was significantly higher in primary hippocampal cells, whereas the amount of LDH was unaffected. We conclude that the cell viability can be restored in this cell type by blocking IRAP with the potent macrocyclic inhibitor HA08, although the mechanism by which HA08 exerts its effects remains unclear

Trisubstituted Imidazoles as Mycobacterium tuberculosis Glutamine Synthetase Inhibitors

Mycobacterium tuberculosis glutamine synthetase (MtGS) is a promising target for antituberculosis drug discovery. In a recent high-throughput screening study we identified several classes of MtGS inhibitors targeting the ATP-binding site. We now explore one of these classes, the 2-tert-butyl-4,5-diarylimidazoles, and present the design, synthesis, and X-ray crystallographic studies leading to the identification of MtGS inhibitors with submicromolar IC(50) values and promising antituberculosis MIC values