TY - JOUR
A1 - Matera, Carlo
A1 - Kauk, Michael
A1 - Cirillo, Davide
A1 - Maspero, Marco
A1 - Papotto, Claudio
A1 - Volpato, Daniela
A1 - Holzgrabe, Ulrike
A1 - De Amici, Marco
A1 - Hoffmann, Carsten
A1 - Dallanoce, Clelia
T1 - Novel Xanomeline-containing bitopic ligands of muscarinic acetylcholine receptors: design, synthesis and FRET investigation
JF - Molecules
N2 - In the last few years, fluorescence resonance energy transfer (FRET) receptor sensors have contributed to the understanding of GPCR ligand binding and functional activation. FRET sensors based on muscarinic acetylcholine receptors (mAChRs) have been employed to study dual-steric ligands, allowing for the detection of different kinetics and distinguishing between partial, full, and super agonism. Herein, we report the synthesis of the two series of bitopic ligands, 12-Cn and 13-Cn, and their pharmacological investigation at the M\(_1\), M\(_2\), M\(_4\), and M\(_5\) FRET-based receptor sensors. The hybrids were prepared by merging the pharmacophoric moieties of the M\(_1\)/M\(_4\)-preferring orthosteric agonist Xanomeline 10 and the M\(_1\)-selective positive allosteric modulator 77-LH-28-1 (1-[3-(4-butyl-1-piperidinyl)propyl]-3,4-dihydro-2(1H)-quinolinone) 11. The two pharmacophores were connected through alkylene chains of different lengths (C3, C5, C7, and C9). Analyzing the FRET responses, the tertiary amine compounds 12-C5, 12-C7, and 12-C9 evidenced a selective activation of M\(_1\) mAChRs, while the methyl tetrahydropyridinium salts 13-C5, 13-C7, and 13-C9 showed a degree of selectivity for M\(_1\) and M\(_4\) mAChRs. Moreover, whereas hybrids 12-Cn showed an almost linear response at the M\(_1\) subtype, hybrids 13-Cn evidenced a bell-shaped activation response. This different activation pattern suggests that the positive charge anchoring the compound 13-Cn to the orthosteric site ensues a degree of receptor activation depending on the linker length, which induces a graded conformational interference with the binding pocket closure. These bitopic derivatives represent novel pharmacological tools for a better understanding of ligand-receptor interactions at a molecular level.
KW - muscarinic acetylcholine receptors
KW - Xanomeline
KW - 77-LH-28-1
KW - bitopic hybrid ligands
KW - synthesis
KW - fluorescence resonance energy transfer
Y1 - 2023
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-311249
SN - 1420-3049
VL - 28
IS - 5
ER -
TY - JOUR
A1 - Seethaler, Marius
A1 - Hertlein, Tobias
A1 - Hopke, Elisa
A1 - Köhling, Paul
A1 - Ohlsen, Knut
A1 - Lalk, Michael
A1 - Hilgeroth, Andreas
T1 - Novel effective fluorinated benzothiophene-indole hybrid antibacterials against S. aureus and MRSA strains
JF - Pharmaceuticals
N2 - Increasing antibacterial drug resistance threatens global health, unfortunately, however, efforts to find novel antibacterial agents have been scaled back by the pharmaceutical industry due to concerns about a poor return on investment. Nevertheless, there is an urgent need to find novel antibacterial compounds to combat antibacterial drug resistance. The synthesis of novel drugs from natural sources is mostly cost-intensive due to those drugs’ complicated structures. Therefore, it is necessary to find novel antibacterials by simple synthesis to become more attractive for industrial production. We succeeded in the discovery of four antibacterial compound (sub)classes accessible in a simple one-pot reaction based on fluorinated benzothiophene-indole hybrids. They have been evaluated against various S. aureus and MRSA strains. Structure- and substituent-dependent activities have been found within the (sub)classes and promising lead compounds have been identified. In addition, bacterial pyruvate kinase was found to be the molecular target of the active compounds. In conclusion, simple one-pot synthesis of benzothiophene-indoles represents a promising strategy for the search of novel antimicrobial compounds.
KW - antibacterial drug resistance
KW - structure activity
KW - synthesis
KW - inhibition
KW - substituent
Y1 - 2022
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-288253
SN - 1424-8247
VL - 15
IS - 9
ER -
TY - JOUR
A1 - Gehrmann, Robin
A1 - Hertlein, Tobias
A1 - Hopke, Elisa
A1 - Ohlsen, Knut
A1 - Lalk, Michael
A1 - Hilgeroth, Andreas
T1 - Novel small-molecule hybrid-antibacterial agents against S. aureus and MRSA strains
JF - Molecules
N2 - Ongoing resistance developments against antibiotics that also affect last-resort antibiotics require novel antibacterial compounds. Strategies to discover such novel structures have been dimerization or hybridization of known antibacterial agents. We found novel antibacterial agents by dimerization of indols and hybridization with carbazoles. They were obtained in a simple one-pot reaction as bisindole tetrahydrocarbazoles. Further oxidation led to bisindole carbazoles with varied substitutions of both the indole and the carbazole scaffold. Both the tetrahydrocarbazoles and the carbazoles have been evaluated in various S. aureus strains, including MRSA strains. Those 5-cyano substituted derivatives showed best activities as determined by MIC values. The tetrahydrocarbazoles partly exceed the activity of the carbazole compounds and thus the activity of the used standard antibiotics. Thus, promising lead compounds could be identified for further studies.
KW - antibacterial activity
KW - synthesis
KW - substituent
KW - structure–activity
KW - inhibition
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-252371
SN - 1420-3049
VL - 27
IS - 1
ER -
TY - JOUR
A1 - Seethaler, Marius
A1 - Hertlein, Tobias
A1 - Wecklein, Björn
A1 - Ymeraj, Alba
A1 - Ohlsen, Knut
A1 - Lalk, Michael
A1 - Hilgeroth, Andreas
T1 - Novel small-molecule antibacterials against Gram-positive pathogens of Staphylococcus and Enterococcus species
JF - Antibiotics
N2 - Defeat of the antibiotic resistance of pathogenic bacteria is one great challenge today and for the future. In the last century many classes of effective antibacterials have been developed, so that upcoming resistances could be met with novel drugs of various compound classes. Meanwhile, there is a certain lack of research of the pharmaceutical companies, and thus there are missing developments of novel antibiotics. Gram-positive bacteria are the most important cause of clinical infections. The number of novel antibacterials in clinical trials is strongly restricted. There is an urgent need to find novel antibacterials. We used synthetic chemistry to build completely novel hybrid molecules of substituted indoles and benzothiophene. In a simple one-pot reaction, two novel types of thienocarbazoles were yielded. Both indole substituted compound classes have been evaluated as completely novel antibacterials against the Staphylococcus and Enterococcus species. The evaluated partly promising activities depend on the indole substituent type. First lead compounds have been evaluated within in vivo studies. They confirmed the in vitro results for the new classes of small-molecule antibacterials.
KW - antibacterial activity
KW - synthesis
KW - substituent
KW - structure-activity
KW - inhibition
Y1 - 2019
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-193130
SN - 2079-6382
VL - 8
IS - 4
ER -
TY - JOUR
A1 - Ashraf, Kerolos
A1 - Yasrebi, Kaveh
A1 - Hertlein, Tobias
A1 - Ohlsen, Knut
A1 - Lalk, Michael
A1 - Hilgeroth, Andreas
T1 - Novel effective small-molecule antibacterials against \(Enterococcus\) strains
JF - Molecules
N2 - \(Enterococcus\) species cause increasing numbers of infections in hospitals. They contribute to the increasing mortality rates, mostly in patients with comorbidities, who suffer from severe diseases. \(Enterococcus\) resistances against most antibiotics have been described, including novel antibiotics. Therefore, there is an ongoing demand for novel types of antibiotics that may overcome bacterial resistances. We discovered a novel class of antibiotics resulting from a simple one-pot reaction of indole and \(o\)-phthaldialdehyde. Differently substituted indolyl benzocarbazoles were yielded. Both the indole substitution and the positioning at the molecular scaffold influence the antibacterial activity towards the various strains of \(Enterococcus\) species with the highest relevance to nosocomial infections. Structure-activity relationships are discussed, and the first lead compounds were identified as also being effective in the case of a vancomycin resistance.
KW - medicine
KW - antibacterial activity
KW - synthesis
KW - derivatives
KW - structure-activity
KW - lead structure
Y1 - 2017
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-172628
VL - 22
IS - 12
ER -
TY - INPR
A1 - Stennett, Tom E.
A1 - Bissinger, Philipp
A1 - Griesbeck, Stefanie
A1 - Ullrich, Stefan
A1 - Krummenacher, Ivo
A1 - Auth, Michael
A1 - Sperlich, Andreas
A1 - Stolte, Matthias
A1 - Radacki, Krzysztof
A1 - Yao, Chang-Jiang
A1 - Würthner, Frank
A1 - Steffen, Andreas
A1 - Marder, Todd B.
A1 - Braunschweig, Holger
T1 - Near-Infrared Quadrupolar Chromophores Combining Three-Coordinate Boron-Based Superdonor and Superacceptor Units
T2 - Angewandte Chemie, International Edition
N2 - In this work, two new quadrupolar A-π-D-π-A chromophores have been prepared featuring a strongly electron- donating diborene core and strongly electron-accepting dimesitylboryl F(BMes2) and bis(2,4,6-tris(trifluoromethyl)phenyl)boryl (BMes2) end groups. Analysis of the compounds by NMR spectroscopy, X-ray crystallography, cyclic voltammetry and UV-vis-NIR absorption and emission spectroscopy indicated that the compounds possess extended conjugated π-systems spanning their B4C8 cores. The combination of exceptionally potent π-donor (diborene) and π- acceptor (diarylboryl) groups, both based on trigonal boron, leads to very small HOMO-LUMO gaps, resulting in strong absorption in the near-IR region with maxima in THF at 840 and 1092 nm, respectively, and very high extinction coefficients of ca. 120,000 M-1cm-1. Both molecules also display weak near-IR fluorescence with small Stokes shifts.
KW - boron
KW - near-IR chromophores
KW - conjugation
KW - low-valent compounds
KW - synthesis
Y1 - 2019
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-180391
N1 - This is the pre-peer reviewed version of the following article: T. E. Stennett, P. Bissinger, S. Griesbeck, S. Ullrich, I. Krummenacher, M. Auth, A. Sperlich, M. Stolte, K. Radacki, C.-J. Yao, F. Wuerthner, A. Steffen, T. B. Marder, H. Braunschweig, Angew. Chem. Int. Ed. 2019, 58, 6449. , which has been published in final form at https://doi.org/10.1002/anie.201900889. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.
ER -
TY - JOUR
A1 - Darwish, Hany W.
A1 - Attia, Mohamed I.
T1 - New spectrofluorimetric methods for determination of melatonin in the presence of N-{2-[1-({3-[2-(acetylamino)ethyl]-5-methoxy-1H-indol-2-yl}methyl)-5-methoxy-1H-indol-3-yl]ethyl} acetamide: a contaminant in commercial melatonin preparations
JF - Chemistry Central Journal
N2 - Background: Melatonin (MLT) has many health implications, therefore it is of valuable importance to develop specific analytical methods for determination of MLT in the presence of its main contaminant, N-{2-[1-({3-[2(acetylamino)ethyl]-5-methoxy-1H-indol-2-yl}methyl)-5-methoxy-1H-indol-3-yl]ethyl}acetamide (10). For development of these analytical methods, compound 10 had to be prepared in an adequate amount.
Results: Compound 10 was synthesized in six steps starting from 5-methoxyindole-2-carboxylic acid (1). Analytical performance of the proposed spectrofluorimetric methods was statistically validated with respect to linearity, accuracy, precision and specificity. The proposed methods were successfully applied for the assay of MLT in laboratory prepared mixtures containing up to 60 % of compound 10 and in commercial MLT tablets with recoveries not less than 99.00 %. No interference was observed from common pharmaceutical additives and the results were favorably compared with those obtained by a reference method.
Conclusions: This work describes simple, sensitive, and reliable second derivative spectrofluorimetric method in addition to two multivariate calibration methods, principal component regression (PCR) and partial least square (PLS), for the determination of MLT in the presence of compound 10.
KW - melatonin
KW - commercial preparations
KW - spectrofluorimetry
KW - synthesis
KW - contaminants
Y1 - 2012
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-134606
VL - 6
IS - 36
ER -
TY - JOUR
A1 - Attia, Mohamed I.
A1 - Herdeis, Claus
A1 - Bräuner-Osborne, Hans
T1 - GABA(B)-Agonistic Activity of Certain Baclofen Homologues
JF - Molecules
N2 - Baclofen (1) is a potent and selective agonist for bicuculline-insensitive GABAB receptors and is used clinically as an antispastic and muscle relaxant agent. In the search for new bioactive chemical entities that bind specifically to GABAB receptors, we report here the synthesis of certain baclofen homologues, namely (R,S)-5-amino-3-arylpentanoic acid hydrochlorides (R,S)-1a–h as well as (R,S)-5-amino-3-methylpentanoic acid [(RS)-1i] to be evaluated as GABABR agonists. Compound 1a is an agonist to GABAB receptors with an EC50 value of 46 μM on tsA201 cells transfected with GABAB1b/GABAB2/Gqz5, being the most active congener among all the synthesized compounds.
KW - pharmacological evaluation
KW - synthesis
KW - GABA
KW - baclofen homologues
KW - GABAB receptor agonists
Y1 - 2013
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-129690
VL - 18
IS - 9
ER -
TY - JOUR
A1 - Tacke, Reinhold
A1 - Lange, Hartwig
A1 - Bentlage, Anke
A1 - Sheldrick, William S.
A1 - Ernst, Ludger
T1 - 2.2.5.5-Tetraorganyl-1.4-dioxa-2.5-disilacyclohexane/2,2,5,5-Tetraorganyl-1,4-dioxa-2,5-disilacyclohexanes
JF - Zeitschrift für Naturforschung B
N2 - The 2,2,5,5-tetraorganyl-1,4-dioxa-2,5-disilacyclohexanes 2a-2c were prepared by condensation of the corresponding (hydroxymethyl)diorganylsilanes 1 a-1 c. The constitution of the heterocycles was confirmed by elemental analyses, cryoscopic measurements, mass spectrometry, and NMR-spectroscopic \((^1H, ^{13}C)\) investigations. The molecular structure of 2 b was determined by X-ray diffraction analysis.
KW - 1,4-Dioxa-2
KW - 5-disila-cyclohexane ring system
KW - synthesis
KW - structure
Y1 - 1983
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-128423
VL - 38
IS - 2
ER -
TY - THES
A1 - Wahler, Johannes
T1 - Borole als Synthesebausteine für neue Organoborverbindungen
T1 - Boroles as Synthetic Building Blocks for novel Organoboron Compounds
N2 - Die vorliegende Arbeit befasst sich mit der Synthese neuer Borolderivate des Typs Ph4C4BR' (R' = Substituent am Borzentrum). Zudem wurde die Reaktivität ausgewählter Borole gegenüber Lewis-Basen, gesättigten und ungesättigten Substraten sowie unter Reduktionsbedingungen untersucht. Auf diese Weise konnten neue Strategien für die Synthese von Bor-haltigen konjugierten Systemen erschlossen werden. Alle wichtigen Strukturmotive wurden durch Multikern-NMR-Spektroskopie in Lösung sowie durch Einkristall-Röntgenstrukturanalyse im Festkörper charakterisiert.
N2 - The present work addresses the synthesis of novel borole derivatives derived from the Ph4C4BR' framework (R' = substituent at boron). Furthermore, the reactivity of selected boroles towards Lewis bases, saturated and unsaturated substrates as well as under reduction conditions was analyzed. Within this context new strategies for the synthesis of conjugated organoboron compounds were developed. All major structural motifs were characterized by multinuclear NMR spectroscopy in solution as well as single crystal X-ray diffraction in the solid state.
KW - Chemische Synthese
KW - Borole
KW - Reaktivität
KW - Radikal-Anion
KW - Carboran
KW - synthesis
KW - boron
KW - reactivity
KW - borole
KW - radical anion
KW - carborane
KW - Borolderivate
KW - Bor
KW - Synthese
Y1 - 2013
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-84095
ER -
TY - THES
A1 - Markl, Christian
T1 - Neue mono- und dimere Melatonin-Analoga als subtypselektive Liganden der Melatoninrezeptoren
T1 - Novel mono- and dimeric melatonin analogues as subtype selective melatonin receptor ligands
N2 - Die vorliegende Arbeit befasst sich mit der Synthese von Liganden der Melatonin-Rezeptoren (MR). Die zwei humanen MR-Subtypen, MT1 und MT2, gehören zur Familie der G-Protein-gekoppelten Rezeptoren. Als „Schlafhormon“ wirkt es schlafinduzierend und vermittelt den circadianen Rhythmus. Zum genauen Verständnis der physiologischen Funktionen der MT1- und MT2-Rezeptoren ist die Verfügbarkeit von subtypselektiven MR-Liganden unentbehrlich. Zum Design von MT2-selektiven MR-Liganden modifizierte man die Melatonin-Grundstruktur durch formale Substitution in 2-Stellung, z.B. mit dem 2-Methylen-N-methyl-anilin- oder 2-Methylen-1´-indol-Rest. Weiterhin wurden trizyklische Derivate mit 1,2,3,4-Tetrahydro-pyrazino[1,2-a]indol- oder 2,3,4,5-Tetrahydro-1H-[1,4]diazepino[1,2-a]indol-Grundgerüst hergestellt. Das Synthesekonzept für dieses Teilprojekt basierte auf dem Synthesebaustein 3-Cyanomethyl-5-methoxy-1H-indol-2-carbonsäure. Da bislang nur wenige MT1-selektive MR-Liganden bekannt sind, wurde zur Untersuchung der Voraussetzung für MT1-Selektivität, die 5-Methoxygruppe von Melatonin formal durch Phenylalkyloxy-Reste verschiedener Kettenlängen substituiert. Die Synthese der Derivate erfolgte ausgehend von N-Acetylserotonin. Als Referenzverbindung wurde der bis heute MT1-selektivste MR-Antagonist (Descamps-Francois et al. 2003) hergestellt. Zu dessen Synthese benötigte man Agomelatin als Ausgangsverbindung. Eine neuartige vierstufige Route zu Agomelatin wurde daher entwickelt. Die Testung der Referenzverbindung ergab eine drastische Abweichung vom Literaturwert, da diese als nahezu unselektiv getestet wurde. Unter den O-Phenylalkyl-N-Acetylserotonin-Derivaten wurden zwei Verbindungen mit einer 11-fachen MT1-Selektivität getestet. Zur Absicherung der Reinheit wurden die Verbindungen mit RP-HPLC untersucht. Schließlich wurden noch melatoninerge Dimere mit einem 1-1´, 1-2´ und 5-5´ Verknüpfungsmuster hergestellt.
N2 - The present work is focused on the synthesis of ligands of melatonin receptors (MR). The two human MR subtypes, MT1 and MT2, belong to the family of G-protein-coupled receptors. As a “sleep hormone”, it induces sleep and also moderates the circadian rhythm. An accurate characterization of melatonin receptor-mediated functions requires MT1 and MT2 selective ligands. In order to design MT2-selective MR-ligands the melatonin scaffold was formally substituted in 2-position, for example with methylen-N-methyl-aniline- or methylen-1´-indole. Furthermore, tricyclic derivatives with the 1,2,3,4-tetrahydro-pyrazino[1,2-a]indole- or 2,3,4,5-tetrahydro-1H-[1,4]diazepino[1,2-a]indole-scaffold were synthesized. The synthetic concept based on the useful building block 3-cyanomethyl-5-methoxy-1H-indole-2-carboxylic acid. While many series of MT2-selective agents are known, the design of MT1-selective agents still is a challenge. A common structural feature of MT1-selective ligands is the presence of a bulky hydrophobic substituent linked to an alkyl chain in a position topologically equivalent to the MeO-group of melatonin. In order to probe the melatonin receptors for MT1-selectivity, a series of melatonin analogues obtained by the replacement of the ether methyl group with phenylalkyl substituents was prepared. The derivates were synthesized from N-acetylserotonine as a starting compound. The most MT1-selective MR-antagonist (Descamps-Francois et al. 2003) was synthesized additionally as a reference compound. Therefore we need agomelatine as starting material, which could be received from our newly developed four-step route. Surprisingly, the reference compound displayed a much lower affinity for the MT1 receptor than reported earlier. In the homologous series of melatonin analogs, the compound with Ph(CH2)3- and PhO(CH2)3-groups were the most MT1-selective agents, revealing that a C3-spacer is optimal to generate MT1-selectivity. Finally, three series of dimeric melatonin analogues, with a 1-1´-, 1-2´- and 5-5´-junction patter were prepared.
KW - G-Protein gekoppelte Rezeptoren
KW - Melatonin
KW - Analoga
KW - Indolderivate
KW - Melatonin-Analoga
KW - Melatoninrezeptorliganden
KW - Agomelatin
KW - dimere Liganden
KW - Synthese
KW - Indolderivate
KW - Synthese
KW - Selektivität
KW - melatonin analogues
KW - melatonin receptor ligands
KW - agomelatine
KW - dimeric ligands
KW - synthesis
Y1 - 2011
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-54618
N1 - Die in der Dissertation beschriebene neue Synthese von Agomelatin wurde
unter:
https://www.thieme-connect.com/ejournals/abstract/synthesis/doi/10.1055/s-0030-1258968
veröffentlicht
ER -
TY - THES
A1 - Merdanovic, Melisa
T1 - Charakterisierung von NadR : das essentielle Enzym der NAD-Synthese bei Haemophilus influenzae
T1 - Characterization of NadR: an essential enzyme of NAD synthesis in Haemophilus influenzae
N2 - I Zusammenfassung Haemophilus influenzae, ein Gram-negatives, Bakterium der Familie Pasteurellaceae, kann beim Menschen eine Vielzahl an Erkrankungen auslösen: Die bekapselte Stämme, v. a. mit Typ b Kapsel können Cellulitis, septische Arthritis, Epiglottitis und Meningitis verursachen. Die nicht-bekapselte Stämme können Otitis media, Sinusitis, Pneumonie und in selteneren Fällen Bakterämie verursachen. Ein besonderes Merkmal des Metabolismus von H. influenzae ist dessen Unfähigkeit Nikotinamid-Adenin-Dinukleotid (NAD+) de novo zu synthetisieren. Daher sind die Enzyme bzw. Transporter, die an NAD+ Aufnahme und Resynthese beteiligt sind, als putative antimikrobielle Ziele von Interesse. In unserer Arbeitsgruppe konnte gezeigt werden, dass NAD+ zu Nikotinamidribosyl degradiert werden muss, bevor es in die Zelle aufgenommen werden kann. Auch Proteine, die an der Degradation des exogenen NAD+ zu Nikotinamidribosyl und dessen anschließender Aufnahme in die Zelle verantwortlich sind, konnten identifiziert und charakterisiert werden. Wie Nikotinamidribosyl im Cytoplasma wiederum zu NAD+ synthetisiert wird, ist auch erst kürzlich geklärt worden: für NadR konnte sowohl eine Ribosyl-Nukleotid-Kinase (RNK) Aktivität als auch eine Nikotinamid-Mononukleotid-Adenylyltransferase (NMNAT) Aktivität in vitro gezeigt werden. Die Kristallstruktur von hiNadR im Komplex mit NAD+ wurde auch aufgeklärt. In dieser Arbeit sollte NadR, insbesondere dessen RNK Domäne, in vivo und in vitro näher charakterisiert werden. Um zu untersuchen, ob beide Domänen in vivo essentiell sind, wurden Deletionsmutanten erzeugt, bei welchen die komplette bzw. der C-terminale Teil der RNK Domäne fehlten. Diese Deletionen konnten im nadV+ Hintergrund erzeugt werden. Die Deletionen konnten in H. influenzae nur zusammen mit dem nadV-Gen transferiert werden oder alternativ nur in die Zellen, die mit pNadRKan Plasmid transformiert wurden. Dies verdeutlicht, dass nicht nur die NMNAT Domäne sondern auch die RNK Domäne bzw. sogar nur wenige C-terminal fehlende Aminosäuren des NadR Proteins essentiell für die Lebensfähigkeit von H. influenzae sind. Gleichzeitig zeigen diese Experimente, dass die RNK-Domäne in Anwesenheit von NadV redundant ist. Ein weiterer Phänotyp der RNK-Deletionsmutante zeigte sich beim Nikotinamidribosyl-Transport. Im Gegensatz zum Wt, welcher ca. 60-80% des 14C-Nikotinamidribosyls aufnahm, konnte für die RNK-Deletionsmutante nur 2-5% Aufnahme gemessen werden. Dies konnte durch das pNadRKan Plasmid komplementiert werden. Weiterhin wurde festgestellt, dass spontan Aminopyridin-resistente H. influenzae Zellen Mutationen im nadR Gen haben, insbesondere im Walker A-Motif (P-Loop) der RNK Domäne. Zusätzlich konnte in dieser Arbeit gezeigt werden, dass NadR aus Aminopyridin und ATP Aminopyridin-Adenin-Dinukleotid synthetisieren kann. Somit konnte gezeigt werden, dass die wachstumshemmende Wirkung eigentlich durch das aus Aminopyridin synthetisierte Aminopyridin-Adenin-Dinukleotid entsteht, welches NAD+ in Redox-Reaktionen verdrängt, wodurch es letztendlich zum Stillstand des Metabolimus kommt. Durch Einführen von gezielten AS-Substitutionen im Walker A und B Motif und in der LID-Domäne von NadR, konnten einige Aminosäuren identifiziert werden, welche essentiell für die Aktivität der RNK Domäne sind. Alle Aminosäuren-Substitutionen führten zum Verlust der RNK Aktivität, die NMNAT Aktivität jedoch war nicht beeinträchtigt. Desweiteren wurden diese NadR Punktmutanten in vivo untersucht. Für alle konnte eine signifikante Defizienz in der Nikotinamidribosyl-Aufnahme beobachtet werden, die gemessene Aufnahme lag im Bereich der RNK-Deletionsmutante. Dadurch konnte eine direkte Korrelation zwischen der RNK Aktivität und der Nikotinamidribosyl-Aufnahme gezeigt werden. In weiteren in vitro Experimenten konnte für NadR eine Feedback-Inhibition durch das NAD+ gezeigt werden, wobei NAD+ in erster Linie die RNK Domäne von NadR inhibiert. Eine graduelle Erhöhung der NAD+ Konzentration führte in den in vitro Assays zu einer graduellen Abnahme der RNK. Bei der NMNAT Aktivität jedoch zeigte sich keine signifikante Inhibition in Anwesenheit von NAD+. Begleitende in vivo Experimente, zeigten eine 2/3 Reduktion der Nikotinamidribosyl-Aufnahme bei den Zellen, die mit NAD+ inkubiert wurden, d. h. höhere intrazelluläre NAD+ Konzentration hatten. Für die genauere Analyse der Feedback-Inhibition durch NAD+ wurden weitere Punktmutanen hergestellt. Bei zwei der Punktmutanten wurde eine Beeinträchtigung der NadR-Aktivität beobachtet, daher wurden diese Punktmutanten von weiteren Analysen im Bezug auf NAD+-Feedback Inhibition ausgeschlossen. Eine Mutante (NadRW256F) jedoch, zeigte ähnliche Aktivität wie das Wt-NadR. In Anwesenheit von NAD+ wurde die RNK Aktivität dieser Punktmutante, im Gegensatz zum Wt-Protein, kaum gehemmt. Dadurch konnte W256 als eine der Aminosäuren identifiziert werden, die an der Vermittlung der NAD+-bedingten Inhibition der RNK-Domäne beteiligt ist.
N2 - I Summary Haemophilus influenzae, a gram-negative human pathogen belonging to a family of Pasteurellaceae is a causative agent of several distinct diseases. Whereas capsulated strains, particulary those with tybe b capsule can cause severe invasive infections such as cellulitis, septic arthrithis, epiglottitis and meningitis, non-capsulated strains generally tend to cause localized disease including otitis media, sinusitis, pneumonia and in rare cases bacteremia. The inability to synthesize NAD+ de novo is one of the hallmarks of H. influenzae metabolism, therefore proteins involved in NAD+ uptake and utilization respresent interesting putative targets for development of novel antimicrobial treatment. In our lab we were able to show, that prior to uptake, NAD+ has to be degraded to NR. Several proteins involved in NAD+ degradation and NR uptake were identified and characterized: OmpP2 (an outer-membrane porin), e(P4) (a membrane-bound acid phosphoesterase), NadN (a periplasmatic nucleotidase) and PnuC (a nicotinamidribosyl transporter localized in inner membrane). Enzyme responsible for resynthesis of nicotinamidribosyl to NAD+ was recently found to be NadR: A bifunctional protein containing a nicotinamidribosyl kinase (RNK) and a nicotinamid mononucleotide adenylyltransferase (NMNAT) activity, both of which were confirmed in vitro. Also, the crystal structure of NadR complexed with NAD+ was recently resolved. The aim of this work was to characterize the in vivo function of NadR, particular interest was laid on the characterization of the nicotinamidribosyl kinase domain. To test if both domains of NadR are essential for survival, deletion mutants lacking the entire RNK domain and the C-terminal 58 amino acids were constructed. Initially, these mutants were made in a H. influenzae strain which contains a chromosomal copy of H. ducreyi nadV gene. In following transformation experiments, transfer of the RNK deletion mutants to H. influenzae strain was always accompanied with an nadV transfer as well. Only in strain containing pNadRKan plasmid, no nadV transfer along with RNK-deletions took place. Indirectly, this shows that not only the entire RNK domain is essential for H. influenzae, but also the last 58 amino acids as well. It also shows that in presence of NadV the RNK domain is redundant. RNK deletion mutant displayed a significant deficiency in nicotinamidribosyl transport as well: whereas the Wt strain can accumulate up to 80% of 14C labeled nicotinamidribosyl, RNK mutant is able to accumulate only 2-5%. Introduction of pNadRKan plasmid to RNK mutant restored transport efficiency to Wt level. Studies using spontanous 3-aminopyridine (3-AmPR) resistant H. influenzae isolates, revealed that almost all 3-AmPR resistant isolates have mutations in the nadR gene. A clustering of mutations in Walker A motif of the RNK domain could be observed. Further studies represented in this work, show that 3-AmPR can act as a subtrate for NadR, therefore in ATP consuming reactions aminopyridine-adenindinucleotide can be synthesized. Intracellular aminopyridine-adenindinucleotide replaces NAD+ in redox reactions, which ultimately leads to inhibition of cell metabolism, thereby explaining the mechanism of 3-AmPR based growth inhibition. Using site-directed mutagenesis to introduce amino acid substitutions in distinct parts of the NadR-RNK domain, active sites of the RNK domain were revealed and amino acids essential for the RNK activity were identified. These defined amino acid exchanges resulted in loss of the RNK activity in vitro, but had no effect on the NMNAT activity, which remained intact in these mutant variants of NadR. Following in vivo studies revealed that all mutant NadR proteins caused a severe nicotinamidribosyl uptake deficiency, similar to the one observed in the RNK deletion mutant. Therefore, a direct correlation between the RNK activity and nicotinamidribosyl uptake was shown. Further in vitro studies revealed a feedback inhibition of NadR by NAD+, especially for the RNK domain. In case of RNK domain a gradual increase of NAD+ concentration led to gradual decrease in RNK activity. In contrast, for NMNAT domain no significant inhibition in the presence of NAD+ was observed. Also, in in vivo experiments a 3 fold reduction of nicotinamidribosyl uptake rate was observed when intracellular NAD+ concentrations were higher. To adress the mechanism of NAD+ feedback inhibition, once again, distinct amino acid exchanges were introduced. In vitro, two of the mutant proteins were impaired in their activity, especially if lower protein contrations were used. Therefore, further test concerning inhibtion were not preformed with these mutants. However, a W256F protein displayed activity similar to that of the native protein and furthermore was not inhibited in presence of NAD+. This indicates an involvement of the amino acid W256 in mediating the NAD+ dependent feedback inhibition on NadR activity.
KW - Haemophilus influenzae
KW - NAD
KW - Synthese
KW - NAD
KW - Enzym
KW - Synthese
KW - Haemophilus
KW - influenzae
KW - NAD
KW - enzyme
KW - synthesis
KW - Haemophilus
KW - influenzae
Y1 - 2005
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-14907
ER -
TY - THES
A1 - Mohrschladt, Christian J.
T1 - Synthese und Untersuchung der photochemischen und photophysikalischen Eigenschaften Donor-Akzeptor-substituierter Anthracenderivate
T1 - Synthesis and Analysis of the Photochemical and Photophysical Properties of Donor-acceptor-substituted Anthracene Derivatives
N2 - In der vorliegenden Arbeit wurde gezeigt, dass Donor-Akzeptor-substituierte Anthracen- und Ethenoanthracenderivate bemerkenswerte photophysikalische und photochemische Eigenschaften aufweisen. So bieten derartige Anthracenderivate eine interessante Grundlage sowohl zur Entwicklung von Fluoreszenzsonden beispielsweise für Schwermetallionen wie auch zur Entwicklung von molekularen Schaltern für die Datenverarbeitung. Weiterhin stellen die untersuchten Anthracene und Ethenoanthracene hervorragende Systeme zur systematischen Untersuchung von Substituenteneinflüssen auf Photoreaktionen dar.
N2 - It has been demonstrated that donor-acceptor-substituted anthracene and ethenoanthracene derivatives exhibit remarkable photophysical and photochemical properties. Such anthracene derivatives serve as an useful basis for the development of fluorescence sensor e.g. for metall ions as well as molecular switches for data processing. Moreover, the anthracenes and ethenoanthracenes present excellent systems for systematic investigation of substituent effects on photoreactions.
KW - Anthracenderivate
KW - Photochemie
KW - Photophysik
KW - Anthracenderivate
KW - Synthese
KW - Fluoreszenzschalter
KW - Dibenzobarrelene
KW - Photochemie
KW - Anthracene derivatives
KW - synthesis
KW - fluorescence switches
KW - dibenzobarrelenes
KW - photochemistry
Y1 - 2003
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-8486
ER -
TY - THES
A1 - Attia, Mohamad Ibrahim
T1 - Design, synthesis and pharmacological evaluation of certain GABAB agonists
T1 - Design, Synthese und pharmakologische Untersuchungen der GABAB-Agonisten
N2 - Ziel dieser Arbeit war die Synthese von (RS)-5-Amino-3-aryl(methyl)-pentansäure Hydrochloride, 3-Aminomethyl-5-chlor-benzolsäure Hydrochlorid und(RS)-4-Amino-3-(4´-ethynyl(jod)-phenyl)-butansäure Hydrochloride und die Testung der pharmakologischen Aktivität dieser Verbindungen. Die synthetisierten Verbindungen wurden als GABAB-Rezeptor Agonisten, in einem auf Ca2+-Messungen basierenden Funktional-Assay (in vitro tsA Zellen mit GABAB1b/GABAB2/Gαq-z5 transfektiert), getestet und daraus ein Struktur-Aktivitäts Modell abgeleitet. Im allgemein Teil dieser Arbeit wird ein Überblick, über die Neurotransmitter- Rezeptoren (Liganden gesteuerte Ionen-Kanal-Rezeptoren und G Protein-gekoppelte Rezeptoren) des zentralen Nervensystems und deren Agonisten und Antagonisten, gegeben. Eine ausführliche Diskussion zur Synthesestrategie der Verbindungen der Zwischenstufen und der Ausgangsmaterialien wird in den Schemata 2-6 beschrieben. Die synthetisierten Verbindungen wurden als GABAB Agonisten geprüft. Zusätzlich wurden diese im 3D Homologie Modell mit FlexiDock Programm gedockt. Daraus wurde ein Modell zur Voraussage der Aktivität von Analogen und Homologen des Baclofens abgeleitet. Letztendlich wurde ein Pharmakophor-Modell für GABAB Agonisten mit DISCO (DIStance COmparisons) Programm erstellt.
N2 - Synthesis of (RS)-5-amino-3-aryl (methyl)-pentanoic acid hydrochlorides, 3 aminomethyl-5-chloro-benzoic acid hydrochloride and (RS)-4-amino-3-(4`-ethynyl(iodo)-phenyl)-butanoic acid hydrochlorides have been accomplished. The aim of their synthesis was to evaluate their GABABR agonist activity and to derive a model which will correlate their structure with the observed pEC50. The GABABR agonist activity of the prepared compounds has been determined in functional assay based on calcium measurement in vitro using tsA cells transfected with GABAB1b/GABAB2/Gαq-z5. Reviews on the neurotransmitter receptors (ligand-gated ion channel receptors and G protein-coupled receptors), their agonists and antagonists have been given in the general part of this work. A detailed discussion on the strategy followed for the synthesis of the designed compounds as well as the starting materials and intermediates has been described and illustrated in Schemes 2-6. The synthesized compounds were evaluated for their GABABR agonist activity. Furthermore, these compounds were docked in the available 3D homology model of GABABR using the program FlexiDock implemented in SYBYL software. Subsequently, we derived a predictive model which correlates the experimentally determined pEC50 with the calculated binding energy of certain baclofen analogues and homologues. In addition, we used the program DISCO (DIStance COmparisons) implemented in SYBYL software to find the pharmacophore features of GABAB agonists.
KW - Baclofen
KW - Analoga
KW - GABA-Rezeptor-Agonist
KW - Pharmakologie
KW - GABAB
KW - Sythese
KW - Baclofen
KW - Pharmakologie
KW - Molekular Modeling
KW - GABAB
KW - synthesis
KW - baclofen
KW - pharmacology
KW - molecular modeling
Y1 - 2003
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-7551
ER -
TY - THES
A1 - Kelm, Bernd
T1 - A New Synthesis of enantiopure C-3-substituted Glutamates by Utilization of Ortho Ester protected (S)-Pyroglutamic acid
T1 - Eine neue Synthese enantiomerenreiner C-3-substituierter Glutamate unter der Verwendung Orthoester-geschützter (S)-Pyroglutaminsäure
N2 - Priority tasks of the present thesis were to generate various enantiopure C-3-substituted pyroglutamates as well as C-3-substituted glutamates, and furthermore to ameliorate the serious drawback of the bad atom-economy in the reaction sequence of previously published silylether-mediated procedures. To meet these requirements, the ortho ester functionality (OBO ester) developed by Corey was introduced. According to the plan of synthesis, the starting material, non-racemic (S)-pyroglutamic acid, was converted to the corresponding oxetane ester via a DCC-mediated esterification. The latter was N-protected to provide N-acceptor substituted pyroglutamic acid oxetane esters (Acceptor=Boc,Cbz,CO2Me). After rearrangement with boron trifluoride, the ortho ester derivatives (Acceptor=Cbz,CO2Me) were at hand and exclusively the N-Cbz derivative was converted to the corresponding alpha,beta-unsaturated lactam via a syn-elimination reaction. The formation of the C-3-substituted ortho ester compounds (R=methyl,ethyl,butyl,allyl,phenyl,4-chlorophenyl,biphenyl,naphthyl) was performed via a copper-mediated conjugate addition to the alpha,beta-enone system of the N-Cbz-alpha,beta-unsaturated lactam. The OBO functionality hence was envisaged to support perfect trans selectivity in this cuprate addition to the Michael system of the N-Cbz-alpha,beta-unsaturated lactam. Spectroscopic NMR-data, on the basis of 1H-, 13C- and DEPT spectra, proved the assumption that the C-3-substituted ortho ester derivatives exclusively are trans-configurated, i.e. the alkyl derivatives (R=methyl,ethyl,butyl,allyl) are (2S,3S)-configurated and the aryl derivatives (R=phenyl,4-chlorophenyl,biphenyl,naphthyl) are (2S,3R)-configurated). The C-3-substituted ortho ester derivatives were completely deprotected to yield the C-3-substituted pyroglutamates (R=ethyl,phenyl,4-chlorophenyl,naphthyl). Finally, ring opening reaction via route A-2 lead to the desired enantiopure C-3-substituted glutamates. Alternatively, latter preferably were reacted via route A-1 to yield the C-3-substituted glutamates (R=methyl,ethyl,butyl,phenyl,4-chlorophenyl,naphthyl). Their (2S,3R)-configuration (R=aryl) and (2S,3S)-configuration (R=alky), respectively, unambiguously was proved on the basis of available spectroscopic NMR-data. To ensure this assumption, diastereomeric (2S,3R)-3-methyl glutamic acid (i.e. cis-configurated) examplarily was synthesized via route A-3 and spectroscopic NMR-data was compared to that of (2S,3S)-3-methyl glutamic acid (i.e. trans-configurated). Conclusively, there can be recorded the fact that the serious drawback of the bad atom-economy in the reaction sequence previously used can be circumvented by the introduction of the OBO functionality, so the concept of an improved atom-economy is achieved. Additionally, in comparison to the silyl-ether-mediated synthesis, the OBO functionality provided crystalline ortho ester derivatives, which facilitated their purification as well as characterization.
N2 - Schwerpunkte dieser Arbeit lagen in der Synthese verschiedener enantiomerenreiner C-3-substituierter Pyroglutamate als auch Glutamate und desweiteren darin, die unzulängliche Wirtschaftlichkeit der bereits bekannten Silylether-vermittelten Methode zu verbessern. Um diesen Anforderungen gerecht zu werden, wurde die von Corey entwickelte Orthoester-Funktionalität (OBO Ester) eingeführt. Dem Syntheseplan entsprechend wurde die Ausgangskomponente, nicht-razemische (S)-Pyroglutaminsäure, über eine DCC-vermittelteVeresterung zum entsprechenden Oxetanester umgesetzt. Dieser wurde daraufhin N-geschützt, wobei die N-Akzeptor-substituierten Pyroglutaminsäureoxetanester(Akzeptor=Boc,Cbz,CO2Me) erhalten wurden. Nach der Umlagerung dieser Ester mit Bortrifluorid wurden die Orthoester-Derivate (Akzeptor=Cbz,CO2Me) erhalten, wobei sich ausschliesslich das N-Cbz Derivat über eine syn-Eliminierungsreaktion zum entsprechenden alpha,beta-ungesättigten Lactam umsetzen liess. Die C-3-substituierten Orthoester-Derivate (R = Methyl,Ethyl,Butyl,Allyl,Phenyl,4-Chlorphenyl,Biphenyl,Naphthyl) wurden über eine kupferkatalysierte 1,4-Addition an das alpha,beta-Enon-System des alpha,beta-ungesättigten Orthoester-Derivats erhalten. Hiebei war zu erwarten, dass die OBO-Funktionalität ausschliesslich trans-Selektivität bei der Cuprat-Addition an das Michael System dieses Derivats gewährleistet. 1H-, 13C- und DEPT-Spektren und die daraus erhaltenen Daten lieferten den Beweis, dass die C-3-substituierten Orthoester-Derivate ausschliesslich trans-Konfiguration aufwiesen, d.h. die Alkylderivate (R=Methyl,Ethyl,Butyl,Allyl) sind (2S,3S)-konfiguriert bzw. die Arylderivate (R=Phenyl,4-Chlorphenyl,Biphenyl,Naphthyl) (2S,3R)-konfiguriert. Die C-3-substituierten Orthoester-Derivate wurden vollständig entschützt, um die C-3-substituierten Pyroglutamate (R=Ethyl,Phenyl,4-Chlorphenyl,Naphthyl) zu erhalten. Schliesslich führte eine Ringöffnungsreaktion über Route A-2 zu den gewünschten enantiomerenreinen C-3-substituierten Glutamaten. Alternativ wurden diese Glutamate (R=Methyl,Ethyl,Butyl, Phenyl,4-Chlorphenyl,Naphthyl) auf eine einfachere Art und Weise über Route A-1 aus den entsprechenden C-3-substituierten Orthoester-Derivaten gewonnen. Deren (2S,3R)-Konfiguration (R=aryl) bzw. (2S,3S)-Konfiguration (R=alkyl) wurde anhand verfügbarer spectroskopischer NMR-Daten überprüft. Um diese Vermutung zu untermauern, wurde beispielhaft (2S,3R)-3-Methylglutaminsäure (i.e. cis-konfiguriert) über Route A-3 synthetisiert und deren spectroskopische NMR-Daten mit denen von (2S,3S)-3-Methylglutaminsäure (i.e. trans-konfiguriert) verglichen. Zusammenfassend lässt sich feststellen, dass der Nachteil der unzulänglichen Wirtschaftlichkeit früherer Synthesen durch die Einführung der OBO-Funktionalität umgangen werden kann, so dass letztendlich das Konzept einer verbesserten „atom-economy“ erreicht wurde. Zusätzlich lieferte die OBO-Funktionalität im Vergleich mit Silylether-Synthesen den Vorteil kristalliner Orthoester-Produkte, was sowohl die Aufarbeitung als auch deren Charakterisierung erleichterte.
KW - Glutamate
KW - Stereoselektive Synthese
KW - Pyroglutaminsäure
KW - Glutamate
KW - C-3-substituiert
KW - enantiomerenrein
KW - Pyroglutaminsäure
KW - Synthese
KW - glutamates
KW - C-3-substituted
KW - enantiopure
KW - pyroglutamic acid
KW - synthesis
Y1 - 2002
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-1296
ER -