Anja Sandström

Synthesis of novel aryl and heteroaryl acyl sulfonimidamides via Pd-catalyzed carbonylation using a nongaseous precursor.

Hitherto unexplored aryl and heteroaryl acyl sulfonimidamides have been prepared through the development of a new Pd-catalyzed carbonylation protocol. This novel methodology, employing sulfonimidamides as nucleophiles and CO gas ex situ released from solid Mo(CO)6 in a sealed two-chamber system, yields a wide range of carbamate protected acyl sulfonimidamides in good to excellent yields.

New developments in the discovery of agents to treat hepatitis C.

Hepatitis C virus (HCV) has deceived researchers for seventeen years now and although the current therapy regimen has been optimized by the development of pegylated interferon-alpha and the addition of ribavirin, no new agent to treat HCV infected patients has yet reached the market. A new era is approaching the HCV research due to new developments for the propagation of the virus in a cell-based system, which may lead to new drug innovations. Efforts in the search of new treatments for HCV infected patients are either focused on direct antiviral drugs, targeting the structural components or enzymes encoded by the virus, or indirect antiviral drugs, targeting host cell components (immunomodulators etc.). An inspection of the drug pipeline for HCV reveals representatives from both classes and of different mechanisms of action. Among the direct acting antiviral agents, inhibitors of the NS3 protease, the NS5B polymerase, and the viral RNA are the most intensively explored. However, there is also on-going and promising preclinical research, in different stages, on other potential targets as the structural protein E2 (for cell-entry inhibitors), the NS3 helicase, the p7 ion-channel, and the multifunctional NS5A protein. The combat of HCV will certainly require a combination of drugs of different mechanisms in order to reduce the emergence of resistance. The latest developments in the discovery of agents to treat HCV are reviewed, with special focus on direct small-molecule antiviral drugs, from a medicinal chemistry perspective.

Structure of a hepatotoxic pentapeptide from the cyanobacterium Nodularia spumigena

The structure of a hepatotoxic peptide from the cyanobacterium Nodularia spumigena was determined using 1D and 2D proton nuclear magnetic resonance spectroscopy and fast atom bombardment mass spectrometry. The toxin was a cyclic pentapeptide (mol. wt 824.5) with the structure cyclo-(beta-methylisoAsp-Arg-Adda-isoGlu-N-methylde hydrobutyric acid) (Adda: 3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid).

Effects on protease inhibition by modifying of helicase residues in hepatitis C virus nonstructural protein 3

This study of the full‐length bifunctional nonstructural protein 3 from hepatitis C virus (HCV) has revealed that residues in the helicase domain affect the inhibition of the protease. Two residues (Q526 and H528), apparently located in the interface between the S2 and S4 binding pockets of the substrate binding site of the protease, were selected for modification, and three enzyme variants (Q526A, H528A and H528S) were expressed, purified and characterized. The substitutions resulted in indistinguishable Km values and slightly lower kcat values compared to the wild‐type. The Ki values for a series of structurally diverse protease inhibitors were affected by the substitutions, with increases or decreases up to 10‐fold. The inhibition profiles for H528A and H528S were different, confirming that not only did the removal of the imidazole side chain have an effect, but also that minor differences in the nature of the introduced side chain influenced the characteristics of the enzyme. These results indicate that residues in the helicase domain of nonstructural protein 3 can influence the protease, supporting our hypothesis that full‐length hepatitis C virus nonstructural protein 3 should be used for protease inhibitor optimization and characterization. Furthermore, the data suggest that inhibitors can be designed to interact with residues in the helicase domain, potentially leading to more potent and selective compounds.

The interaction of the 2′-OH group with the vicinal phosphate in ribonucleoside 3′-ethylphosphate drives the sugar-phosphate backbone into unique (S,ω−) conformational state

Abstract The analysis of temperature-dependent vicinal proton-proton coupling constants has shown that the North (N)South (S) pseudorotational equilibria of ribonucleoside 3′-ethylphosphates [ApEt (21), GpEt (22), CpEt(23), rTpEt (24) and UpEt (25)], modelling simple diribonucleoside(3′ → 5′)monophosphate without any intramolecular base-base stacking, are driven more towards the South-type sugar (S) by ΔΔ11° = −2.5 kJ mol−1 in the case of purine and by ≈ −3.8 kJ mol−1 in the case of pyrimidine nucleotides compared to the corresponding parent ribonucleosides 1 - 5. In contrast, the S-type sugar conformation in 2′-deoxyribonucleoside 3′-ethylphosphates (ref. 3d) is stabilized by ΔΔH ° ≈ −1.9 kJ mol−1 in both purine and pyrimidine nucleotides compared to the parent 2′-deoxyribonucleosides. The total energetic effect of 2′-OH group due to its interaction with the vicinal phosphate in ribonucleotides in contrast with the corresponding 2′ -deoxynucleotide counterparts can be assessed by subtracting the free-energies of NS pseudorotational equilibria in the ribonucteotide analogs 21 – 25 from the corresponding 2′-deoxynucleotide counterparts 16 – 20: ΔΔG298 ≈ +0.3 kJ mol−1 in ApEt (21), +0.6 kJ mol−1 in GpEt (22), +2.1 kJ mol−1 CpEt (23), +1.1 kJ mol−1 in rTpEt (24) and +1.3 kJ mol−1 in UpEt (25). The additional stabilization of the S-type pseudorotamers in ribonucleoside 3′-ethylphosphates 21 – 25 compared to ribonucleoside 3′-monophosphates 11–15 by ΔΔH ° ≈ -2.0 kJ mol−1 is attributed to the influence of the 2′-OH group in the former. The population of ω1 rotamers increases by 7–13% from 278 to 358K, which corresponds also with an equal increase of the population of N-type pseudorotamers, suggesting a unique cooperativity in the two-state (N,ω1)(S,ω−) conformational equilibria in 21 – 25. These cooperative conformational transitions of (N,ω1)(S,ω−) equilibrium in 21 – 25 have been found to be orchestrated by the interaction of 2′-hydroxyl group with the vicinal phosphate as evident by the non-equivalent methylene protons of the 3′-ethylester function uplo 348K in 21 – 25 compared to the 2′-deoxynucleotide counterparts 16 – 20 (ref. 3d). The intramolecular interaction of the 2′-OH function with the vicinal phosphodiester stabilizes the S and ω− conformers (“On” switch), whereas 2′-OH in a non-interacting stale stabilizes the N and ω1 conformers (“Off switch) in 21 – 25. The strengths of this “On-Off” molecular switch for the preference of (S,ω−) conformational slate over (N,ω1) slate in 21 – 25 are as follows: ΔG298 ≈ −2.8 kJ mol−1 for adenosine 3′-ethylphosphate (21), −2.1 kl mol−1 for guanosine 3′-ethylphosphate (22), ≈ 0.1 kJ mol−1 for cytidine 3′-ethylphosphate (23), −0.9 kJ mol−1 for ribothymidine 3′-ethylphosphate (24) and −0.7 kJ mol−1 for uridine 3′-ethylphosphaie (25).

Spectroscopic, kinetic and semiempirical molecular orbital studies on 8-amino-, 8-methylamino- & 8-dimethylamino-adenosines

Summary: Kinetic studies on acidic depurination of 8-aminoadenosine, 8-methylaminoadenosine, and 8dimethylaminoadenosine show their relative rates are respectively 2.7,2 and 429,fold with respect ta adenosine. Structural consequence of 8-amino, 8-methylamino or 8-dimethylamino group in the g-substituted purine nucleosides have been therefore investigated in order to delineate the injluence of these d-amino substituents on the relative rate of cleavage of glycosyl bond under acidic condition by both IsN- and IH-NMR spectroscopy in neutral and acidic solutions. ISN-NiUR studies showed that the relative amount of protonation at Nl in 8-amine adenosine and B-methylaminoadenosine are 66% (4470 N’H+) and 8.5% (15% N’H+), respectively, while it is 96% (4% N7H+) in case of 8-dimethylaminoadenosine. IH-NMR studies also showed some differences in conformation of sugar moiety of nucleosides in acidic solution in comparison with their con

The dipeptide Phe-Phe amide attenuates signs of hyperalgesia, allodynia and nociception in diabetic mice using a mechanism involving the sigma receptor system

ormations in neutral solution. Semiempirical Molecular Orbital calculations have been used to throw light on steric and electronic factors dictated by a-amino, 8-methylamino or 8-dimethylamino group across CB-N8 bond that control the stabilization of N7H+ versus NlH+ species. Result from these Semiempirical Molecular Orbital calculations have been subsequently assessed with those obtained by IsN-NMR studies. Successful rational design of new analogues of nucleosides which should interfere specifically with the biosynthesis of DNA or RNA in cancer cells or virus- or parasite-infected cells requires that the effect of specific structural modification in these analogues on the chemical reactivities, hydrolytic stabilitities, and conformational properties in solution are clearly defined. In this respect, we considered 8-aminoadenosine, 8methylaminoadenosine, and 8-dimethylaminoadenosine as useful target nucleosides because of the following reasons. Lipophilic derivatives of cytosine and guanosine have been shown to form Watson-Crick type base pairs in nonaqueous solvents over a wide temperature range suggesting that the monomers can be used to understand and possibly to predict structures of polymeric nucleic acids’, since low dielectric solvents mimic the dielectric environment of the interior of a nucleic acid double helix. Lipophilic derivatives of 8-amino-2’deoxyadenosine and 8-methylamino-2’-deoxyadenosine are expected to form both Watson-Crick and Hcogsteen type base pairs with lipophilic thymidine derivative in non-polar solution while 8-dimethylamino-2’deoxyadenosine should not. Our initial studies on the base-pairing abilities of lipophilic 8-amino-2’deoxyadenosine derivative with lipophilic thymidine derivative in CDC13 have shown that their hydrogenbonded complexation in 1: 1 and 1: 2 molar stoicheiometries at -20 “C are differentx. These studies have indicated that oligonucleotide based on 8-amino-2’-deoxyadenosine or 8-methylamino-2’-deoxyadenosine should form intermolecular DNA triplexes which have been shown to be important because of their potential role in chromosome mapping3 and in antisense gene therapfl. Our unpublished work has shown that the glycosidic bond of 8-amino-2’-deoxyadenosine [8-A-2,&I] and 8-methylamino-2’-deoxyadenosine [8-mA-2’-dA] are -10 times more acid-labile than that of the parent 2’-deoxyadenosine, which suggests that no acid-labile protecting group can be used in the synthesis of [8-A-2’-dA 18 & [S-mA-2’-dA]g. These observations prompted us to study the structural properties of 8-amino- & 8-alkylamino substituted adenosine and guanosine derivatives in

Hepatitis C virus NS3 protease inhibitors comprising a novel aromatic P1 moiety.

BackgroundPrevious studies have demonstrated that intrathecal administration of the substance P amino-terminal metabolite substance P1-7 (SP1-7) and its C-terminal amidated congener induced antihyperalgesic effects in diabetic mice. In this study, we studied a small synthetic dipeptide related to SP1-7 and endomorphin-2, i.e. Phe-Phe amide, using the tail-flick test and von Frey filament test in diabetic and non-diabetic mice.ResultsIntrathecal treatment with the dipeptide increased the tail-flick latency in both diabetic and non-diabetic mice. This effect of Phe-Phe amide was significantly greater in diabetic mice than non-diabetic mice. The Phe-Phe amide-induced antinociceptive effect in both diabetic and non-diabetic mice was reversed by the σ1 receptor agonist (+)-pentazocine. Moreover, Phe-Phe amide attenuated mechanical allodynia in diabetic mice, which was reversible by (+)-pentazocine. The expression of spinal σ1 receptor mRNA and protein did not differ between diabetic mice and non-diabetic mice. On the other hand, the expression of phosphorylated extracellular signal-regulated protein kinase 1 (ERK1) and ERK2 proteins was enhanced in diabetic mice. (+)-Pentazocine caused phosphorylation of ERK1 and ERK2 proteins in non-diabetic mice, but not in diabetic mice.ConclusionsThese results suggest that the spinal σ1 receptor system might contribute to diabetic mechanical allodynia and thermal hyperalgesia, which could be potently attenuated by Phe-Phe amide.

Small peptides mimicking substance P (1-7) and encompassing a C-terminal amide functionality.

Inhibition of the hepatitis C virus (HCV) NS3 protease has emerged as an attractive approach to defeat the global hepatitis C epidemic. In this work, we present the synthesis and biochemical evaluation of HCV NS3 protease inhibitors comprising a non-natural aromatic P(1) moiety. A series of inhibitors with aminobenzoyl sulfonamides displaying submicromolar potencies in the full-length NS3 protease assay was prepared through a microwave-irradiated, palladium-catalyzed, amidocarbonylation protocol.

Discovery of dipeptides with high affinity to the specific binding site for substance P1-7.

Some of the biological effects demonstrated after administration of substance P (SP) in vivo can indirectly be attributed to the fragmentation of the undecapeptide to its N-terminal bioactive fragment SP(1-7). This heptapeptide (H-Arg-Pro-Lys-Pro-Gln-Gln-Phe-OH) is a major bioactive metabolite from SP that frequently exerts similar biological effects as the parent peptide but also, in several cases, completely opposite actions. Specific binding sites for the heptapeptide SP(1-7) that are separate from the SP preferred NK receptors have been identified. In this study we demonstrate that (a) the C-terminal part of the SP metabolite SP(1-7) is most important for binding as deduced from an Ala scan and that a replacement of Phe(7) for Ala is deleterious, (b) truncation of the N-terminal amino acid residues of SP(1-7) delivers peptides with retained binding activity, although with somewhat lower binding affinities than SP(1-7) and (c) a C-terminal amide group as a replacement for the terminal carboxy group of SP(1-7) and for all of the truncated ligands synthesized affords approximately 5-10-fold improvements of the binding affinities.