Systematic Dissection of an Aminopyrrolic Cage Receptor for β‐Glucopyranosides Reveals the Essentials for Effective Recognition

A set of structures designed for the recognition of glucosides has been obtained by systematically destructuring a tripodal aminopyrrolic cage receptor that selectively recognizes octyl‐β‐D ‐glucopyranoside (OctβGlc). NMR spectroscopy and isothermal titration calorimetry binding measurements showed that cleavage of one pillar of the cage was beneficial to the binding properties of the receptor, as long as two residual amino groups of the cleaved pillar were present. Removal of these two residual amino groups produced a dramatic loss of affinity for OctβGlc of the resulting monocyclic analogue of the parent cage receptor. A significant improvement in the binding ability was achieved by replacing one pillar with two aminopyrrolic hydrogen‐bonding arms, despite the loss of a preorganized structure. In contrast to the cage receptor, recognition of OctβGlc was observed, even in a competitive medium (30 % DMF in chloroform). Structural studies in solution, carried out through NMR spectroscopy and molecular modeling calculations, led to the elucidation of the 3D binding modes of the side‐armed monocyclic receptors; this highlighted the key role of the amino groups and demonstrated the occurrence of a rotaxane‐like complex, which featured the octyl chain of the glucoside threaded through the macrocyclic ring.     

Mass spectrometric characterisation of a condensation product between porphobilinogen and indolyl‐3‐acryloylglycine in urine of patients with acute intermittent porphyria

We document the presence of a previously unknown species in the urine of patients with acute intermittent porphyria (AIP). The compound was fully characterised by liquid chromatography tandem mass spectrometry. Interpretation of both full spectrum acquisition and product ion spectra acquired in positive and negative ionisation modes by quadrupole time of flight MS allowed for the identification of a condensation product arising from porphobilinogen (PBG, increased in the urine of AIP patients) and indolyl‐3‐acryloylglycine (IAG, derived from indolylacrylic acid and present in human urine). The structure was unequivocally confirmed through comparison between the selected reaction monitoring chromatograms obtained from the urinary species and the condensation product qualitatively synthesised in the laboratory. Owing to the large amounts of both PBG and IAG in urine of AIP patients, the possible ex vivo formation of PBG‐IAG in urine samples was evaluated. The product was spontaneously formed at room temperature, at 4 °C and even during storage at ?20 °C when spiking a control sample with PBG. A positive correlation was found between PBG and PBG‐IAG in samples collected from AIP patients. However, no correlation was found between PBG‐IAG and IAG. Purified PBG‐IAG did not form the characteristic chromogen after application of p‐dimethylaminobenzaldehyde in HCl, thus suggesting that the current techniques used to measure PBG in urine of AIP patients based on Ehlrich's reaction do not detect this newly characterised PBG‐IAG fraction. Copyright © 2015 John Wiley & Sons, Ltd.     

Detection and characterization of prednisolone metabolites in human urine by LC‐MS/MS

Glucocorticosteroids are prohibited in sports when used by systemic administrations (e.g. oral), whereas they are allowed using other administration ways. Strategies to discriminate between administrations routes have to be developed by doping control laboratories. For this reason, the metabolism of prednisolone (PRED) was studied using liquid chromatography coupled to tandem mass spectrometry. A single oral (10 mg) dose of PRED was administered to two healthy male volunteers. Urine samples were collected up to 6 days after administration. Samples were hydrolyzed with β‐glucuronidase and subjected to liquid–liquid extraction with ethyl acetate in alkaline conditions. The extracts were analyzed by liquid chromatography coupled to tandem mass spectrometry. Precursor ion scan methods (m/z 77, 91, 105, 121, 147 and 171) in positive ionization and neutral loss scan methods (76 and 94 Da) in negative ionization modes were applied for the open detection of PRED metabolites. Using these methods, PRED parent compound plus 20 metabolites were detected. PRED and 11 metabolites were characterized by comparison with standards of the compounds (PRED, prednisone, 20β‐dihydro‐PRED and 20α‐dihydro‐PRED, 20β‐dihydro‐prednisone and 20α‐dihydro‐prednisone, 6β‐hydroxy‐PRED and 6α‐hydroxy‐PRED, 20β isomers and 20α isomers of 6β,11β,17α,20,21‐pentahydroxypregnan‐1,4‐diene‐3‐one, 6α,11β,17α,20β,21‐pentahydroxypregnan‐1,4‐diene‐3‐one and Δ⁶‐PRED). Using mass spectrometric data, feasible structures were proposed for seven of the remaining nine detected metabolites, including several 6‐hydroxy‐metabolites. Eleven of the characterized metabolites have not been previously described. Maximum excretion rates for PRED metabolites were achieved in first 24 h; however, most of the metabolites were still detectable in the last collected samples (day 6). Copyright © 2015 John Wiley & Sons, Ltd.     

Zur Kenntniss der Röstproducte des Caffees

Ohne Zusammenfassung     

Neue Ventilpipette

Ohne ZusammenfassungKiel, 24. Juni 1895.     

Über einige Derivate des Brenzcatechins

Ohne ZusammenfassungZum Schlusse sei es mir noch gestattet, Herrn Prof. Herzig für all seine Mühe, Freundlichkeit und Umsicht herzlichst zu danken, mit der er diese Arbeit geleitet hat.     

Synthesis of linear and hyperbranched tetrazine-based polyhetarylene assemblies with high nitrogen content

The synthesis of polyhetarylenes containing exclusively s-tetrazine and another nitrogen heterocycle (pyridine or s-triazine) is described. The key step involved the polymerization of a suitable di- or triamidrazone, leading to a linear or hyperbranched dihydrotetrazine-based assembly, respectively. The triazinylenetetrazinylene material stands as one of the most nitrogenated polymers ever described.