TY - THES A1 - Duda, Katharina T1 - Synthesen und Eigenschaften von Dicarba-closo-dodecaboran-Derivaten und ersten gemischten Fluorohydridoborat-Anionen T1 - Syntheses and properties of dicarba-closo-dodecaborane derivatives and first mixed fluorohydridoborate anions N2 - Ein wesentliches Ziel dieser Arbeit war die Durchführung von regioselektiven Deborierungsreaktionen von 1,7-Dicarba-closo-dodecaboranen sowie die Herstellung von polyfunktionalisierten meta-Carboran-Derivaten. Die synthetisierten {nido-7,9-C2B9}- und {closo-1,7-C2B10}-Derivate und ausgewählte ortho-Carboran-Derivate wurden nach erfolgter Kumada-artiger Kreuzkupplungsreaktion bzgl. ihrer Koordinationschemie untersucht. Die ethinylfunktionalisierten Borcluster wurden als Edukte für die Herstellung von Gold(I)-Komplexen genutzt. Weitere Ziele dieser Arbeit waren außerdem die Synthese und umfassende Charakterisierung des gemischten Fluorohydridoborat-Anions [BHF3]− und der carboranylsubstituierten Borat-Anionen [1-HF2B-closo-1,2-C2B10H11]− und [1-HF2B-9,12-I2-closo-1,2-C2B10H9]− sowie die Untersuchung hinsichtlich ihrer Folgechemie. N2 - An essential aim of the presented work was the investigation of regioselective deboronation reactions of 1,7-dicarba-closo-dodecaboranes as well as the preparation of poly-functionalized meta-carboranes. After the {nido-7,9-C2B9}-, {closo-1,7-C2B10}- and selected ortho-carborane derivates were prepared by a Kumada-type cross coupling reaction, the behaviour of these compounds in coordination chemistry was examined. The ethynyl-functionalised boron clusters were used as educts for the preparation of gold(I) complexes. Further objectives of this work were the synthesis and complete characterisation of the mixed fluorohydridoborate anion [BHF3]− and of the carboranyl substituted anions [1-HF2B-closo-1,2-C2B10H11]− and [1-HF2B-9,12-I2-closo-1,2-C2B10H9]− and in further applications in syntheses. KW - Carborane KW - Fluoroborate KW - regioselektive Deborierungsreaktionen KW - Gold(I)-Komplexe KW - gemischte Fluorohydridoborat-Anionen KW - Cluster-Aufbau Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-181038 ER - TY - JOUR A1 - Gentzsch, Christian A1 - Chen, Xinyu A1 - Spatz, Philipp A1 - Košak, Urban A1 - Knez, Damijan A1 - Nose, Naoko A1 - Gobec, Stanislav A1 - Higuchi, Takahiro A1 - Decker, Michael T1 - Synthesis and Initial Characterization of a Reversible, Selective \(^{18}\)F-Labeled Radiotracer for Human Butyrylcholinesterase JF - Molecular Imaging and Biology N2 - Purpose A neuropathological hallmark of Alzheimer's disease (AD) is the presence of amyloid-β (Aβ) plaques in the brain, which are observed in a significant number of cognitively normal, older adults as well. In AD, butyrylcholinesterase (BChE) becomes associated with A\(_{β}\) aggregates, making it a promising target for imaging probes to support diagnosis of AD. In this study, we present the synthesis, radiochemistry, in vitro and preliminary ex and in vivo investigations of a selective, reversible BChE inhibitor as PET-tracer for evaluation as an AD diagnostic. Procedures Radiolabeling of the inhibitor was achieved by fluorination of a respective tosylated precursor using K[\(^{18}\)F]. IC\(_{50}\) values of the fluorinated compound were obtained in a colorimetric assay using recombinant, human (h) BChE. Dissociation constants were determined by measuring hBChE activity in the presence of different concentrations of inhibitor. Results Radiofluorination of the tosylate precursor gave the desired radiotracer in an average radiochemical yield of 20 ± 3 %. Identity and > 95.5 % radiochemical purity were confirmed by HPLC and TLC autoradiography. The inhibitory potency determined in Ellman's assay gave an IC\(_{50}\) value of 118.3 ± 19.6 nM. Dissociation constants measured in kinetic experiments revealed lower affinity of the inhibitor for binding to the acylated enzyme (K2 = 68.0 nM) in comparison to the free enzyme (K\(_{1}\) = 32.9 nM). Conclusions The reversibly acting, selective radiotracer is synthetically easily accessible and retains promising activity and binding potential on hBChE. Radiosynthesis with \(^{18}\)F labeling of tosylates was feasible in a reasonable time frame and good radiochemical yield. KW - Alzheimer’s disease KW - amyloid-β (Aβ) KW - butyrylcholinesterase Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-269870 SN - 1860-2002 VL - 23 IS - 4 ER - TY - JOUR A1 - Gentzsch, Christian A1 - Hoffmann, Matthias A1 - Ohshima, Yasuhiro A1 - Nose, Naoko A1 - Chen, Xinyu A1 - Higuchi, Takahiro A1 - Decker, Michael T1 - Synthesis and Initial Characterization of a Selective, Pseudo‐irreversible Inhibitor of Human Butyrylcholinesterase as PET Tracer JF - ChemMedChem N2 - The enzyme butyrylcholinesterase (BChE) represents a promising target for imaging probes to potentially enable early diagnosis of neurodegenerative diseases like Alzheimer's disease (AD) and to monitor disease progression in some forms of cancer. In this study, we present the design, facile synthesis, in vitro and preliminary ex vivo and in vivo evaluation of a morpholine‐based, selective inhibitor of human BChE as a positron emission tomography (PET) tracer with a pseudo‐irreversible binding mode. We demonstrate a novel protecting group strategy for 18F radiolabeling of carbamate precursors and show that the inhibitory potency as well as kinetic properties of our unlabeled reference compound were retained in comparison to the parent compound. In particular, the prolonged duration of enzyme inhibition of such a morpholinocarbamate motivated us to design a PET tracer, possibly enabling a precise mapping of BChE distribution. KW - carbamate KW - enzyme kinetics KW - fluorine-18 KW - positron emission tomography KW - radiotracers Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-239904 VL - 16 IS - 9 SP - 1427 EP - 1437 ER - TY - JOUR A1 - Krebs, Johannes A1 - Haehnel, Martin A1 - Krummenacher, Ivo A1 - Friedrich, Alexandra A1 - Braunschweig, Holger A1 - Finze, Maik A1 - Ji, Lei A1 - Marder, Todd B. T1 - Synthesis and Structure of an o-Carboranyl-Substituted Three-Coordinate Borane Radical Anion JF - Chemistry—A European Journal N2 - Bis(1-(4-tolyl)-carboran-2-yl)-(4-tolyl)-borane [(1-(4-MeC\(_{6}\)H\(_{4}\))-closo-1,2-C\(_{2}\)B\(_{10}\)H\(_{10}\)-2-)\(_{2}\)(4-MeC\(_{6}\)H\(_{4}\))B] (1), a new bis(o-carboranyl)-(R)-borane was synthesised by lithiation of the o-carboranyl precursor and subsequent salt metathesis reaction with (4-tolyl)BBr\(_{2}\). Cyclic voltammetry experiments on 1 show multiple distinct reduction events with a one-electron first reduction. In a selective reduction experiment the corresponding paramagnetic radical anion 1\(^{.−}\) was isolated and characterized. Single-crystal structure analyses allow an in-depth comparison of 1, 1\(^{.−}\), their calculated geometries, and the S\(_{1}\) excited state of 1. Photophysical studies of 1 show a charge transfer (CT) emission with low quantum yield in solution but a strong increase in the solid state. TD-DFT calculations were used to identify transition-relevant orbitals. KW - Wade’s rules KW - carborane KW - charge transfer KW - radical KW - threecoordinate boron Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256841 VL - 27 IS - 31 ER - TY - JOUR A1 - Brückner, Tobias A1 - Heß, Merlin A1 - Stennett, Tom E. A1 - Rempel, Anna A1 - Braunschweig, Holger T1 - Synthesis of Boron Analogues of Enamines via Hydroamination of a Boron-Boron Triple Bond BT - Dedicated to Professor Wolfgang Kaim on the occasion of his 70th birthday JF - Angewandte Chemie, International Edition N2 - An N-heterocyclic-carbene-stabilized diboryne undergoes rapid, high-yielding and catalyst-free hydroamina- tion reactions with primary amines, yielding 1-amino-2-hydro- diborenes, which can be considered boron analogues of enamines. The electronics of the organic substituent at nitrogen influence the structure and further reactivity of the diborene product. With electron-rich anilines, a second hydroamination can occur at the diborene to generate 1,1-diamino-2,2-dihy- drodiboranes. With isopropylamine, the electronic influence of the alkyl substituent upon the diborene leads to an unprece- dented boron-mediated intramolecular N-dearylation reaction of an N-heterocyclic carbene unit. KW - boron KW - diborynes KW - diborenes KW - DFT KW - enamines KW - hydroamination KW - multiple bonds Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-240669 VL - 60 IS - 2 ER - TY - JOUR A1 - Ferger, Matthias A1 - Berger, Sarina M. A1 - Rauch, Florian A1 - Schönitz, Markus A1 - Rühe, Jessica A1 - Krebs, Johannes A1 - Friedrich, Alexandra A1 - Marder, Todd B. T1 - Synthesis of Highly Functionalizable Symmetrically and Unsymmetrically Substituted Triarylboranes from Bench-Stable Boron Precursors JF - Chemistry—A European Journal N2 - A novel and convenient methodology for the one-pot synthesis of sterically congested triarylboranes by using bench-stable aryltrifluoroborates as the boron source is reported. This procedure gives systematic access to symmetrically and unsymmetrically substituted triarylboranes of the types BAr\(_{2}\)Ar’ and BArAr'Ar’’, respectively. Three unsymmetrically substituted triarylboranes as well as their iridium-catalyzed C−H borylation products are reported. These borylated triarylboranes contain one to three positions that can subsequently be orthogonally functionalized in follow-up reactions, such as Suzuki-Miyaura cross-couplings or Sonogashira couplings. KW - synthetic methods KW - boranes KW - borylation KW - chromophore KW - functionalization Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256827 VL - 27 IS - 35 ER - TY - THES A1 - Ming, Wenbo T1 - Synthesis of α‑Aminoboronates and PBP Pincer Palladium Boryl Complexes T1 - Synthese von α-Aminoboronaten und PBP-Pincer-Palladium-Boryl-Komplexen N2 - The first Borono-Strecker reaction has been developed to synthesize α-aminoboronates via a multicomponent reaction of readily available carbonyl compounds (aldehydes and ketones), amines and B2pin2. The preparation of α-amino cyclic boronates can be achieved via multicomponent coupling of salicylaldehydes, amines, and B2(OH)4. In addition, the diazaborole-based PBP pincer palladium chloride and the diazaborole-based PBP pincer palladium trifluoromethanesulfonate complexes were synthesized and fully characterized for the first time, and used as catalysts for Suzuki-Miyaura cross-coupling reactions. N2 - Wurde die erste Borono-Strecker Reaktion zur Synthese von α-Aminoboronaten, mittels einer Multikomponenten-Reaktion aus leicht zugänglichen Carbonylverbindungen (Aldehyde und Ketone), Aminen und B2pin2, entwickelt. Außerdem gelang die Darstellung von zyklischen α-Aminoboronaten durch Multikomponenten-Kupplung von leicht zugänglichen Salicylaldehyden, Aminen und B2(OH)4. Des Weiteren wurde der Diazaborol-basierte PBP Pincer Palladium Chlorid Komplex und der Diazaborol-basierte PBP Pincer Palladium Trifluoromethylsulfonat Komplex erstmalig synthetisiert, vollständig charakterisiert und als Katalysator für Suzuki-Miyaura Kreuzkupplungen eingesetzt. KW - borylation KW - α-aminoboronates KW - PBP pincer palladium complexes KW - cross-coupling Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-198323 ER - TY - THES A1 - Roos, Markus T1 - Synthesis, Photophysics and Photocatalysis of [FeFe] Complex Containing Dyads and Bimolecular Systems T1 - Synthese, Photophysik und Photokatalyse von [FeFe]-Komplex enthaltenden Dyaden und bimolekularen Systemen N2 - In the course of this work, a total of three photocatalytically active dyads for proton reduction could be synthesized together with the associated individual components. Two of them, D1 and D2, comprised a [Ru(bpy)3]2+ photosensitizer and D3 an [Ir(ppy)2bpy]+ photosensitizer. A Ppyr3-substituted propyldithiolate [FeFe] complex was used as catalyst in all systems. The absorption spectroscopic and electrochemical investigations showed that an inner-dyadic electronic coupling is effectively prevented in the dyads due to conjugation blockers within the bridging units used. The photocatalytic investigations exhibited that all dyad containing two-component systems (2CS) showed a significantly worse performance than the corresponding bimolecular three-component systems (3CS). Transient absorption spectroscopy showed that the 2CS behave very similarly to the associated multicomponent systems during photocatalysis. The electron that was intended for the intramolecular transfer from the photosensitizer unit to the catalyst unit within the dyads remains at the photosensitizer for a relatively long time, analogous to the 3CS and despite the covalently bound catalyst. It is therefore assumed that this intramolecular electron transfer is likely to be hindered as a result of the weak electronic coupling caused by the bridge units used. Instead, the system bypasses this through an intermolecular transfer to other dyad molecules in the immediate vicinity. In addition, with the help of emission quenching experiments and electrochemical investigations, it could be clearly concluded that all investigated systems proceed via the reductive quenching mechanism during photocatalysis. N2 - Im Rahmen dieser Arbeit konnten insgesamt drei photokatalytisch aktive Dyaden zur Protonenreduktion zusammen mit den zugehörigen Einzelkomponenten synthetisiert werden. Zwei von ihnen, D1 und D2, umfassten einen [Ru(bpy)3]2+-Photosensibilisator und D3 einen [Ir(ppy)2bpy]+-Photosensibilisator. Als Katalysator wurde in allen Systemen ein Ppyr3-substituierter Propyldithiolat-[FeFe]-Komplex verwendet. Die absorptionsspektroskopischen und elektrochemischen Untersuchungen zeigten, dass eine innerdyadische elektronische Kopplung aufgrund von Konjugationsblockern innerhalb der verwendeten Brückeneinheiten wirksam verhindert wird. Die photokatalytischen Untersuchungen zeigten, dass alle dyadenhaltigen Zweikomponentensysteme (2CS) eine signifikant schlechtere Leistung zeigten als die entsprechenden bimolekularen Dreikomponentensysteme (3CS). Mithilfe der transienten Absorptionsspektroskopie konnte gezeigt werden, dass sich die 2CS während der Photokatalyse sehr ähnlich wie die zugehörigen Mehrkomponentensysteme verhalten. Das Elektron, das für den intramolekularen Transfer von der Photosensibilisatoreinheit zur Katalysatoreinheit innerhalb der Dyaden vorgesehen war, verbleibt analog zu den 3CS und trotz des kovalent gebundenen Katalysators relativ lange am Photosensibilisator. Es wird daher angenommen, dass dieser intramolekulare Elektronentransfer wahrscheinlich aufgrund der schwachen elektronischen Kopplung, die durch die verwendeten Brückeneinheiten verursacht wird, behindert wird. Stattdessen umgeht das System dies durch einen intermolekularen Transfer zu anderen Dyadenmolekülen in unmittelbarer Nähe. Darüber hinaus konnte mithilfe von Emissionslöschungsexperimenten und elektrochemischen Untersuchungen eindeutig darauf geschlossen werden, dass alle untersuchten Systeme während der Photokatalyse über den reduktiven Löschmechanismus ablaufen. KW - Fotokatalyse KW - Elektronentransfer KW - proton reduction KW - [FeFe] hydrogenase mimic KW - dyad KW - ruthenium photosensitizer KW - iridium photosensitizer KW - Protonenreduktion KW - [FeFe]-Hydrogenase Imitator KW - Dyade KW - Ruthenium-Photosensibilisator KW - Iridium-Photosensibilisator Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-234537 ER - TY - JOUR A1 - Berger, Sarina M. A1 - Ferger, Matthias A1 - Marder, Todd B. T1 - Synthetic Approaches to Triarylboranes from 1885 to 2020 JF - Chemistry – A European Journal N2 - In recent years, research in the fields of optoelectronics, anion sensors and bioimaging agents have been greatly influenced by novel compounds containing triarylborane motifs. Such compounds possess an empty p‐orbital at boron which results in useful optical and electronic properties. Such a diversity of applications was not expected when the first triarylborane was reported in 1885. Synthetic approaches to triarylboranes underwent various changes over the following century, some of which are still used in the present day, such as the generally applicable routes developed by Krause et al. in 1922, or by Grisdale et al. in 1972 at Eastman Kodak. Some other developments were not pursued further after their initial reports, such as the synthesis of two triarylboranes bearing three different aromatic groups by Mikhailov et al. in 1958. This review summarizes the development of synthetic approaches to triarylboranes from their first report nearly 135 years ago to the present. KW - arylmetalate KW - boranes KW - chromophore KW - Lewis acid KW - synthetic methods Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-238952 VL - 27 IS - 24 SP - 7043 EP - 7058 ER - TY - JOUR A1 - Mayr, Stefan A1 - Klein, Igor A1 - Rutzinger, Martin A1 - Kuenzer, Claudia T1 - Systematic water fraction estimation for a global and daily surface water time-series JF - Remote Sensing N2 - Fresh water is a vital natural resource. Earth observation time-series are well suited to monitor corresponding surface dynamics. The DLR-DFD Global WaterPack (GWP) provides daily information on globally distributed inland surface water based on MODIS (Moderate Resolution Imaging Spectroradiometer) images at 250 m spatial resolution. Operating on this spatiotemporal level comes with the drawback of moderate spatial resolution; only coarse pixel-based surface water quantification is possible. To enhance the quantitative capabilities of this dataset, we systematically access subpixel information on fractional water coverage. For this, a linear mixture model is employed, using classification probability and pure pixel reference information. Classification probability is derived from relative datapoint (pixel) locations in feature space. Pure water and non-water reference pixels are located by combining spatial and temporal information inherent to the time-series. Subsequently, the model is evaluated for different input sets to determine the optimal configuration for global processing and pixel coverage types. The performance of resulting water fraction estimates is evaluated on the pixel level in 32 regions of interest across the globe, by comparison to higher resolution reference data (Sentinel-2, Landsat 8). Results show that water fraction information is able to improve the product's performance regarding mixed water/non-water pixels by an average of 11.6% (RMSE). With a Nash-Sutcliffe efficiency of 0.61, the model shows good overall performance. The approach enables the systematic provision of water fraction estimates on a global and daily scale, using only the reflectance and temporal information contained in the input time-series. KW - earth observation KW - landsat KW - MODIS KW - remote sensing KW - probability KW - Sentinel-2 KW - subpixel KW - water Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-242586 SN - 2072-4292 VL - 13 IS - 14 ER -