Quantitative Determination and Environmental Risk Assessment of 102 Chemicals of Emerging Concern in Wastewater-Impacted Rivers Using Rapid Direct-Injection Liquid Chromatography—Tandem Mass Spectrometry

The rapid source identification and environmental risk assessment (ERA) of hundreds of chemicals of emerging concern (CECs) in river water represent a significant analytical challenge. Herein, a potential solution involving a rapid direct-injection liquid chromatography–tandem mass spectrometry method for the quantitative determination of 102 CECs (151 qualitatively) in river water is presented and applied across six rivers in Germany and Switzerland at high spatial resolution. The method required an injection volume of only 10 µL of filtered sample, with a runtime of 5.5 min including re-equilibration with >10 datapoints per peak per transition (mostly 2 per compound), and 36 stable isotope-labelled standards. Performance was excellent from the low ng/L to µg/L concentration level, with 260 injections possible in any 24 h period. The method was applied in three separate campaigns focusing on the ERA of rivers impacted by wastewater effluent discharges (1 urban area in the Basel city region with 4 rivers, as well as 1 semi-rural and 1 rural area, each focusing on 1 river). Between 25 and 40 compounds were quantified directly in each campaign, and in all cases small tributary rivers showed higher CEC concentrations (e.g., up to ~4000 ng/L in total in the R. Schwarzach, Bavaria, Germany). The source of selected CECs could also be identified and differentiated from other sources at pre- and post- wastewater treatment plant effluent discharge points, as well as the effect of dilution downstream, which occurred over very short distances in all cases. Lastly, ERA for 41 CECs was performed at specific impacted sites, with risk quotients (RQs) at 1 or more sites estimated as high risk (RQ > 10) for 1 pharmaceutical (diclofenac), medium risk (RQ of 1–10) for 3 CECs (carbamazepine, venlafaxine, and sulfamethoxazole), and low risk (RQ = 0.1–1.0) for 7 CECs (i.e., RQ > 0.1 for 11 CECs in total). The application of high-throughput methods like this could enable a better understanding of the risks of CECs, especially in low flow/volume tributary rivers at scale and with high resolution.     

Design,synthesis and biological evaluation of pyridyl substituted benzoxazepinones as potent and selective inhibitors of aldosterone synthase

Exorbitant aldosterone is closely associated with various severe diseases, including congestive heart failure and chronic kidney disease. As aldosterone synthase is the pivotal enzyme in aldosterone biosynthesis, its inhibition constitutes a promising treatment for these diseases. Via a structure-based approach, a series of pyridyl substituted 3,4-dihydrobenzo[f][1,4]oxazepin-5(2H)-ones were designed as inhibitors of aldosterone synthase. Six compounds (5j, 5l, 5m 5w, 5x and 5y) distinguished themselves with potent inhibition (IC₅₀ <100 nmol/L) and high selectivity over homogenous 11β-hydroxylase. As the most promising compound, 5x exhibited an IC₅₀ of 12 nmol/L and an excellent selectivity factor (SF) of 157, which are both superior to those of the reference fadrazole (IC₅₀ = 21 nmol/L, SF = 7). Importantly, 5x showed no inhibition against steroidogenic CYP17, CYP19 and a panel of hepatic CYP enzymes indicating an outstanding safety profile. As it manifested satisfactory pharmacokinetic properties in rats, compound 5x was considered as a drug candidate for further development.     

Fluorescence and Photochemistry of Recombinant Phytochrome from the Cyanobacterium Synechocystis

Fluorescence and photochemical properties of phytochrome from the cyanobacterium Synechocystis were investigated in the temperature interval from 293 to 85 K. The apoprotein was obtained by overexpression in Escherichia coli and assembled to a holophytochrome with phycocyanobilin (PCB) and phytochromobilin (PφB), Syn(PCB)phy and Syn(PφB)phy, respectively. Its red-absorbing form, Pr, is characterized at 85 K by the emission and excitation maxima at 682 and 666 nm in Syn(PCB)phy and at 690 and 674 nm in Syn(PφB)phy. At room temperature, the spectra are blue shifted by 5–10 nm. The fluorescence intensity dropped down by ?15–20-fold upon warming from 85 to 293 K and activation energy of the fluorescence decay was estimated to be ca 5.4 and 4.9 kJ mol^?1 in Syn(PCB)phy and Syn(PφB)phy, respectively. Phototransformation of Pr upon red illumination was observed at temperatures above 160–170 K in Syn(PCB)phy and above 140–150 K in Syn(PφB)phy with a 2–3 nm shift of the emission spectrum to the blue and increase of the intensity of its shorter wavelength part. This was interpreted as a possible formation of the photoproduct of the meta-Ra type of the plant phytochrome. At ambient temperatures, the extent of the Pr phototransformation to the far-red-absorbing form, Pfr, was ca 0.7–0.75 and 0.85–0.9 for Syn(PCB)phy and Syn(PφB)phy, respectively. Fluorescence of Pfr and of the photoproduct similar to lumi-R was not observed. With respect to the photochemical parameters, Syn(PCB)phy and Syn(PφB)phy are similar to each other and also to a small fraction of phyA (phyA″) and to phyB. The latter were shown to have low photochemical activity at low temperatures in contrast to the major phyA pool (phyA″), which is distinguished by the high extent (ca 50%) of Pr photoransformation at 85 K. These photochemical features are interpreted in terms of different activation barriers for the photoreaction in the Pr excited state.     

Synthesis of selenolates from stannyl and silyl alkylselenides

Stannyl and silyl alkylselenides have been efficiently transformed to the corresponding alkylselenolates on reaction with butyllithiums. Other conditions proved to be limited.     

New stereoselective syntheses of cis- and trans-2-methyl-4-arylpiperidines

A stereoselective approach has been developed for the synthesis of cis- and trans-2-methyl-4-arylpiperidines from a common intermediate. The Ni-catalyzed hydrogenolysis of N-Boc-2-methyl-4-aryl-4-piperidinols, obtained by addition of organometallic reagents on N-Boc-2-methyl-4-piperidone, afforded the trans derivatives with up to 95% selectivity whereas the corresponding cis isomers were obtained in the presence of palladium catalysts.     

PHOTOCHROMIC SYNERGISM OF BACTERIORHODOPSIN- and HALORHODOPSIN-MEDIATED PHOTOPHOSPHORYLATION IN Halobacterium halobium*

Quantitative action spectroscopy was performed in Halobacterium halobium. using four suited pigment mutants, namely the bacteriorhodopsin and halorhodopsin positive mutant strain M-l (BR⁺, HR⁺), the bacteriorhodopsin positive but halorhodopsin negative strain M-18 (BR⁺, HR^-), the bacteriorhodopsin negative but halorhodopsin positive strain L-33 (BR^-, HR⁺), and the bacteriorhodopsin and halorhodopsin negative strain L-07 (BR^-, HR⁺). The approached questions were: First, photoenergetic synergism of halorhodopsin and bacteriorhodopsin in intact cells; second, photochromism and cellular function of the blue light-absorbing intermediates, i.e. M-412 and HR-410 in bacteriorhodopsin and in halorhodopsin, respectively. Dark-adapted cells of mutant strain M-l show wavelength-dependency of quantum yield of photo-phosphorylation, φ_ATP. An 1.4-fold enhancement was found at 575 nm wavelength where the long wavelength absorbance bands of bacteriorhodopsin and halorhodopsin intersect. The enhancement vanished after a 30 min pulse of orange light (600 Wm^-2 bandpass from 495 to 750 nm), but was restored after a 30 min pulse of blue light (100 Wm^-2 bandpass from 325 to 480 nm). Photoreversibility of this enhancement probably reflects phototransformation of halorhodopsin from its ground state into its inactive intermediate, HR-410, and vice versa. The halorhodopsin-mediated enhancement with maximum quantum yield of photophosphorylation, φ_ATP= 0.06, i.e. a quantum requirement of = 17 photons/ATP, is partly substituted by a rise in phosphate potential and explained in terms of a voltage-regulated gating effect on the H⁺-driven ATP-synthase, superimposed on the chemiosmotic mechanism of energy coupling. The blue-absorbing photochromic intermediate, M-412 of bacteriorhodopsin, dissipates light energy upon photoexcitation that is reflected by a spectral decline in quantum yield of photophosphorylation to a minimum value of = 0.01 at 415 nm, i.e. a quantum requirement of = 100 photons/ATP.     

Economical Access to Diverse Enantiopure Tetrahydropyridines and Piperidines Enabled by Catalytic Borrowing Hydrogen

We disclose herein a catalytic borrowing hydrogen method that enables an unprecedented, economical one-pot access to enantiopure tetrahydropyridines with minimal reagent use or waste formation. This method couples a few classes of readily available substrates with commercially available 1,3-amino alcohols, and delivers the valuable tetrahydropyridines of different substitution patterns free of N-protection. Such transformations are highly challenging to achieve, as multiple redox steps need to be realized in a cascade and numerous side reactions including a facile aromatization have to be overcome. Highly diastereoselective functionalizations of tetrahydropyridines also result in a general access to enantiopure di- and tri-substituted piperidines, which ranks the topmost frequent N-heterocycle in commercial drugs.     

Structural variations of N-acetylneuraminic acid,part 19: Synthesis of both epimeric pairs of the 4-C-methyl- and 4-deoxy-4-C-methyl- as well as of the β-methylketoside of 4-deoxy-4-C-methylene-N-acetylneuraminic acid

Summary While the reaction of the 4-oxo-Neu 5 Ac derivative2 a with tributoxy methyl zirconate led exclusively to equatorial 4-C-methyl derivative3 a, the analogous reaction with tetramethyl zirconate yielded a 3:2 mixture of both diastereoisomeres3 a and4 a. After removal of protecting groups the 5-acetamido-3,4-dideoxy-4-C-methyl-D-glycero-D-galacto-2-nonulosonic acid5 a and 5-acetamido-3,4-dideoxy-4-C-methyl-D-glycero-D-talo-2-nonulosonic acid6 a were obtained. The 4-C-methylene derivative was prepared by treatment of the same 4-oxo-derivative with CH₂I₂/Zn/Cp ₂ZrCl₂. Subsequent hydrogenation led to both epimeric 4-deoxy-4-C-methyl derivatives8 a and9 a. Final removal of protecting groups gave the 5-acetamido-3,4,5-trideoxy-4-C-methyl-D-glycero-D-galacto-2-nonulosonic acid10 a respectively the 5-acetamido-2,7-anhydro-4-C-methyl-3,4,5-trideoxy-D-glycero-D-talo-2-nonulosonic acid11 a. The -methylketosides of the 4-deoxy-4-C-methyl- (16) and 4-C-methylene-Neu 5 Ac (15) were prepared via the peracetylated derivatives to obtain modell substrates for enzymatic studies. Thus all free acids were tested for inhibition of CMP-sialate synthease. Only the 4-C-methylene compound15 showed most unexpectedly a strong competitive inhibition of this enzyme.

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Strukturelle Abwandlungen an N-Acetylneuraminsäure, 19. Mitt.: Synthese der beiden Epimerenpaare der 4-C-Methyl- und 4-Deoxy-4-C-methyl- sowie des -Methylketosids der 4-Deoxy-4-C-methylen-N-acetylneuraminsäure. Verhalten gegenüber CMP-Sialat-Synthase

Zusammenfassung Während die Umsetzung des 4-Oxoderivates2 a mit (BuO)₃ MeZr ausschließlich zur equatorialen 4-C-Methylverbindung3 a führt, wurde bei der Reaktion mitMe ₄Zr ein 3:2-Gemisch der beiden Diastereomeren3 a und4 a erhalten. Das 4-C-Methylenderivat7 a wurde durch Reaktion derselben 4-Oxoverbindung mit CH₂I₂/Zn/Cp ₂ZrCl₂ erhalten. Eine anschließende Hydrierung (H₂-Pd/C) führte zu einem trennbaren Germisch der beiden 4-Deoxy-4-C-methylderivative8 a und9 a. Diese Verbindungen konnten durch das Entfernen der Schutzgruppen einerseits in die 5-Acetamido-3,4,5-trideoxy-4-C-methyl-D-glycero-D-galacto-2-nonulosonsäure10 a und 5-Acetamido-2,7-anhydro-4-C-methyl-3,4,5-tridoxy-D-glycero-D-talo-2-nonulosonsäure11 a umgewandelt werden. Die Verbindungen Methyl-5-acetamido-4-C-methylen-3,4,5-trideoxy--D-manno-2-nonulopyranosidonat (15) und Methyl-5-acetemido-4-C-methyl-3,4,5-tridoxy--D-glycero-D-talo-2-nonulopyranosidonat (16) wurden als Modellverbindungen für enzymatische Untersuchungen über peracetylierte Zwischenstufen hergestellt. Überraschenderweise zeigte nur die 4-C-Methylenverbindung15 eine starke kompetitive Hemmung gegenüber CMP-Sialat-Synthase.