Matthias Westerhausen

CORM-EDE1: A Highly Water-Soluble and Nontoxic Manganese-Based photoCORM with a Biogenic Ligand Sphere

[Mn(CO)5Br] reacts with cysteamine and 4-amino-thiophenyl with a ratio of 2:3 in refluxing tetrahydrofuran to the complexes of the type [{(OC)3Mn}2(μ-SCH2CH2NH3)3]Br2 (1, CORM-EDE1) and [{(OC)3Mn}2(μ-SC6H4-4-NH3)3]Br2 (2, CORM-EDE2). Compound 2 precipitates during refluxing of the tetrahydrofuran solution as a yellow solid whereas 1 forms a red oil that slowly solidifies. Recrystallization of 2 from water yields the HBr-free complex [{(OC)3Mn}2(μ-S-C6H4-4-NH2)2(μ-SC6H4-4-NH3)] (3). The n-propylthiolate ligand (which is isoelectronic to the bridging thiolate of 1) leads to the formation of the di- and tetranuclear complexes [(OC)4Mn(μ-S-nPr)2]2 and [(OC)3Mn(μ-S-nPr)]4. CORM-EDE1 possesses ideal properties to administer carbon monoxide to biological and medicinal tissues upon irradiation (photoCORM). Isolated crystalline CORM-EDE1 can be handled at ambient and aerobic conditions. This complex is nontoxic, highly soluble in water, and indefinitely stable therein in the absence of air and phosphate buffer. CORM-EDE1 is stable as frozen stock in aqueous solution without any limitations, and these stock solutions maintain their CO release properties. The reducing dithionite does not interact with CORM-EDE1, and therefore, the myoglobin assay represents a valuable tool to study the release kinetics of this photoCORM. After CO liberation, the formation of MnHPO4 in aqueous buffer solution can be verified.

Tris(pyrazolyl)methanides of the Alkaline Earth Metals: Influence of the Substitution Pattern on Stability and Degradation

Trispyrazolylmethanides commonly act as strong tridentate bases toward metal ions. This expected coordination behavior has been observed for tris(3,4,5-trimethylpyrazolyl)methane (1a), which yields the alkaline-earth-metal bis[tris(3,4,5-trimethylpyrazolyl)methanides] of magnesium (1b), calcium (1c), strontium (1d), and barium (1e) via deprotonation of 1a with dibutylmagnesium and [Ae{N(SiMe3)2}2] (Ae = Mg, Ca, Sr, and Ba, respectively). Barium complex 1e degrades during recrystallization that was attempted from aromatic hydrocarbons and ethers. In these scorpionate complexes, the metal ions are embedded in distorted octahedral coordination spheres. Contrarily, tris(3-thienylpyrazolyl)methane (2a) exhibits a strikingly different reactivity. Dibutylmagnesium is unable to deprotonate 2a, whereas [Ae{N(SiMe3)2}2] (Ae = Ca, Sr, and Ba) smoothly metalates 2a. However, the primary alkaline-earth-metal bis[tris(3-thienylpyrazolyl)methanides] of Ca (2c), Sr (2d), and Ba (2e) represent intermediates and degrade under the formation of the alkaline-earth-metal bis(3-thienylpyrazolates) of calcium (3c), strontium (3d), and barium (3e) and the elimination of tetrakis(3-thienylpyrazolyl)ethene (4). To isolate crystalline compounds, 3-thienylpyrazole has been metalated, and the corresponding derivatives [(HPz(Tp))4Mg(Pz(Tp))2] (3b), dinuclear [(tmeda)Ca(Pz(Tp))2]2 (3c), mononuclear [(pmdeta)Sr(Pz(Tp))2] (3d), and [(hmteta)Ba(Pz(Tp))2] (3e) have been structurally characterized. Regardless of the applied stoichiometry, magnesiation of thienylpyrazole 3a with dibutylmagnesium yields [(HPz(Tp))4Mg(Pz(Tp))2] (3b), which is stabilized in the solid state by intramolecular N-H···N···H-N hydrogen bridges. The degradation of [Ae{C(Pz(R))3}2] (R = Ph and Tp) has been studied by quantum chemical methods, the results of which propose an intermediate complex of the nature [{(Pz(R))2C}2Ca{Pz(R)}2]; thereafter, the singlet carbenes ([:C(Pz(R))2]) dimerize in the vicinity of the alkaline earth metal to tetrapyrazolylethene, which is liberated from the coordination sphere as a result of it being a very poor ligand for an s-block metal ion.

Concept for enhancement of the stability of calcium-bound pyrazolyl-substituted methanides.

Metalation of bis(3-thiophen-2-ylpyrazol-1-yl)phenylmethane [2, which is accessible from the reaction of bis(3-thien-2-ylpyrazol-1-yl)methanone (1) with triphosgene] with [(thf)2Ca{N(SiMe3)2}2] in tetrahydrofuran and subsequent crystallization from a mixture of toluene and 1,2-dimethoxyethane yield [(dme)Ca{C(Pz(th))2Ph}{N(SiMe3)2}] (3). The α,α-bis(3-thiophen-2-ylpyrazol-1-yl)benzyl ligand exhibits a κ(2)N,κC-coordination mode with a Ca-C σ-bond length of 262.8(2) pm. The crystalline compound is stable if air and moisture is strictly excluded; however, in solution; this calcium complex slowly degrades.

Fluorescent amphiphilic heterografted comb polymers comprising biocompatible PLA and PEtOx side chains

A series of amphiphilic heterografted comb polymers comprising various ratios of oligomeric polylactide (PLA) and poly(2-ethyl-2-oxazoline) (PEtOx) side chains was synthesized via the grafting-through method employing the reversible addition–fragmentation chain transfer copolymerization. Two well-defined PLA macromonomers were prepared via ring opening polymerization (ROP) of L-lactide using a calcium-based pre-catalyst, pyrenebutanol as an initiator and methacryloyl chloride as an end-capping agent. The PEtOx macromonomer was obtained from the cationic ROP of EtOx and end-capping with methacrylic acid. The amphiphilic comb polymers self-assembled in aqueous solution to form spherical and worm-like micelles, vesicles and more complex morphologies as a function of the composition, as is evident from dynamic light scattering and cryo-transmission electron microscopy studies. All polymers were found to be non-toxic to L929 cells up to a concentration of 200 μg mL−1. Cellular uptake studies with HEK-293 cells by live cell confocal fluorescence microscopy revealed localization in the cytosol after 4 h and suggest an energy-driven cellular uptake mechanism.

Calcium-Mediated Catalytic Synthesis of 1-(Diorganylamino)-1,4-diphenyl-4-(diphenylphosphanyl)buta-1,3-dienes

The hydroamination of diphenylbutadiyne with 1 equiv of the secondary amines HNRR (R/R = Ph/Ph, Ph/Me, and pTol/Me) in the presence of catalytic amounts of the tetrakis(amino)calciate K2[Ca{N(H)Dipp}4] (Dipp = 2,6-diisopropylphenyl) yields the corresponding 1-(diorganylamino)-1,4-diphenylbut-1-ene-3-ynes as a mixture of E/Z isomers. These tertiary alkenylamines react with diphenylphosphane to form RRN-C(Ph)═CH-CH═C(Ph)-PPh2 [R/R = Ph/Ph (1), Ph/Me (2), and pTol/Me (3)] in the presence of catalytic amounts of [(THF)4Ca(PPh2)2] or of the same calciate K2[Ca{N(H)Dipp}4]. Whereas the hydroamination is regio- (amino group in 1-position) but not stereoselective (formation of E and Z isomers), this second hydrofunctionalization step is regio- (phosphanyl group in 4-position) and stereoselective (only E isomers are formed), finally leading to mixtures of (E,E)- and (Z,E)-1-(diorganylamino)-1,4-diphenyl-4-(diphenylphosphanyl)buta-1,3-dienes.

Impact of higher-order heme degradation products on hepatic function and hemodynamics

BACKGROUND & AIMSnBiliverdin and bilirubin were previously considered end products of heme catabolism; now, however, there is evidence for further degradation to diverse bioactive products. Z-BOX A and Z-BOX B arise upon oxidation with unknown implications for hepatocellular function and integrity. We studied the impact of Z-BOX A and B on hepatic functions and explored their alterations in health and cholestatic conditions.nnnMETHODSnFunctional implications and mechanisms were investigated in rats, hepatocytic HepG2 and HepaRG cells, human immortalized hepatocytes, and isolated perfused livers. Z-BOX A and B were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in acute and acute-on-chronic liver failure and hereditary unconjugated hyperbilirubinemia.nnnRESULTSnZ-BOX A and B are found in similar amounts in humans and rodents under physiological conditions. Serum concentrations increased ∼20-fold during cholestatic liver failure in humans (p<0.001) and in hereditary deficiency of bilirubin glucuronidation in rats (p<0.001). Pharmacokinetic studies revealed shorter serum half-life of Z-BOX A compared to its regio-isomer Z-BOX B (p=0.035). While both compounds were taken up by hepatocytes, Z-BOX A was enriched ∼100-fold and excreted in bile. Despite their reported vasoconstrictive properties in the brain vasculature, BOXes did not affect portal hemodynamics. Both Z-BOX A and B showed dose-dependent cytotoxicity, affected the glutathione redox state, and differentially modulated activity of Rev-erbα and Rev-erbβ. Moreover, BOXes-triggered remodeling of the hepatocellular cytoskeleton.nnnCONCLUSIONSnOur data provide evidence that higher-order heme degradation products, namely Z-BOX A and B, impair hepatocellular integrity and might mediate intra- and extrahepatic cytotoxic effects previously attributed to hyperbilirubinemia.nnnLAY SUMMARYnDegradation of the blood pigment heme yields the bile pigment bilirubin and the oxidation products Z-BOX A and Z-BOX B. Serum concentrations of these bioactive molecules increase in jaundice and can impair liver function and integrity. Amounts of Z-BOX A and Z-BOX B that are observed during liver failure in humans have profound effects on hepatic function when added to cultured liver cells or infused into healthy rats.

Retinol initiated poly(lactide)s: stability upon polymerization and nanoparticle preparation

The synthesis of retinol initiated polylactide (PLA) by ring opening polymerization (ROP) of L-lactide via in situ calcium alkoxide formation with all-trans-retinol and Ca[N(SiMe3)2]2(THF)2 is described. PLAs with degree of polymerization (DP) values ranging from 13 to 60 were obtained and characterized in detail by means of 1H nuclear magnetic resonance (NMR) spectroscopy, size exclusion chromatography (SEC), UV/vis spectroscopy and (tandem) mass spectrometry techniques. Stable nanoparticles (NPs) were prepared via a nanoprecipitation method and characterized by DLS and SEM. The stability of retinol upon conjugation to PLA as well as the nanoparticle formulation was investigated in detail and found to be significantly affected by the storage conditions such as exposure to light, oxygen and temperature.

An unsymmetrical phosphonium diylide with a fluorenylidene subunit and its lithium complexes

The phosphonium ylide MePh2P(flu) (3) (flu = C13H8, fluorenylidene) was conveniently prepared by reaction of Ph2P(fluH) (1) (fluH = C13H9, fluorenyl) with iodomethane, followed by subsequent dehydrohalogenation of the resulting phosphonium salt [MePh2P(fluH)]I (2) by potassium tert-butoxide. Compound 3 was further deprotonated by n-butyllithium, yielding the corresponding lithium complex [Li{CH2PPh2(flu)}(tmeda)] (4) in presence of N,N,N′,N′-tetramethylethylenediamine (tmeda). This mononuclear lithium compound contains the monoanionic chelating diylidic ligand. An exchange of the neutral bidentate tmeda by tridentate N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (pmdta) enforces a change in coordination mode. Consequently, the diylide is monodentate in [Li{CH2PPh2(flu)}(pmdta)] (5). Compounds 1–5 were characterized by NMR spectroscopy and single-crystal X-ray diffraction experiments. Graphical abstract

One-pot Synthesis of 3-Aryl-substituted 1-Hydroxy-2-acylindolizines

A new method for the formation of C-C bonds in a one-pot synthesis of 1-hydroxy-2-acyl-3- arylindolizines (acyl: 2-pyridylformyl, thienylformyl; aryl: phenyl, pyridyl, thienyl) from the reaction of 1,3-diketones with aldehydes has been evaluated. X-Ray diffraction studies of single crystals have provided structural information about the so-formed indolizines. In the crystalline state, the hydroxyl units form intra- or intermolecular hydrogen bonds to the acyl functionalities. The color of these indolizines depends on the pH value of the solvent. Graphical Abstract One-pot Synthesis of 3-Aryl-substituted 1-Hydroxy-2-acylindolizines