Ampicillin sodium: Isolation, identification and synthesis of the last unknown impurity after 60 years of clinical use.

Ampicillin, discovered in 1958, was the first broad spectrum semisynthetic penicillin introduced into the market. Despite its wide use not all the impurities have been identified to date. Herein, the last unknown impurity present in commercially available medicines was isolated and identified. This impurity that accounts up to 0.8 in area % by HPLC (EP 10.0) in the Reference Listed Drugs (RLD) was characterized and identified to be the 16-keto penicillin G. The structure was confirmed by comparison with a chemically synthesized sample. The determination of the Relative Response Factor (RRF) of the impurity respect to the parent drug allowed to recalculate the real amount that is consistently below the reporting threshold.

Long-Term Performance Assessment of Low-Cost Atmospheric Sensors in the Arctic Environment.

The Arctic is an important natural laboratory that is extremely sensitive to climatic changes and its monitoring is, therefore, of great importance. Due to the environmental extremes it is often hard to deploy sensors and observations are limited to a few sparse observation points limiting the spatial and temporal coverage of the Arctic measurement. Given these constraints the possibility of deploying a rugged network of low-cost sensors remains an interesting and convenient option. The present work validates for the first time a low-cost sensor array (AIRQino) for monitoring basic meteorological parameters and atmospheric composition in the Arctic (air temperature, relative humidity, particulate matter, and CO2). AIRQino was deployed for one year in the Svalbard archipelago and its outputs compared with reference sensors. Results show good agreement with the reference meteorological parameters (air temperature (T) and relative humidity (RH)) with correlation coefficients above 0.8 and small absolute errors (≈1 °C for temperature and ≈6% for RH). Particulate matter (PM) low-cost sensors show a good linearity (r2 ≈ 0.8) and small absolute errors for both PM2.5 and PM10 (≈1 µg m-3 for PM2.5 and ≈3 µg m-3 for PM10), while overall accuracy is impacted both by the unknown composition of the local aerosol, and by high humidity conditions likely generating hygroscopic effects. CO2 exhibits a satisfying agreement with r2 around 0.70 and an absolute error of ≈23 mg m-3. Overall these results, coupled with an excellent data coverage and scarce need of maintenance make the AIRQino or similar devices integrations an interesting tool for future extended sensor networks also in the Arctic environment.

Novel insights into the chemistry of an old medicine: A general degradative pathway for penicillins from a piperacillin/tazobactam stability study.

Piperacillin is a broad spectrum beta-lactam antibiotic used in combination with tazobactam for hospital-related bacterial infections. The reconstituted solutions must respect the sub-visible and visible particles specifications. It was claimed that the reformulation containing EDTA/sodium citrate was able to control the formation of an insoluble impurity responsible for the formation of particulate matter observed using Ringer Lactate as diluent. The nature of the impurities formed during the degradative process of piperacillin/tazobactam combination has been herein investigated, by exploring the effect of added excipients and pH variations. The exact structure of the isolated dimeric impurity, the penicilloic acid-piperacillin dimer, was determined through complete characterization, allowing to propose a novel degradative general pathway for beta-lactam antibiotics. The presence of EDTA resulted unnecessary to contain the formation of the insoluble impurity, since the use of sodium citrate alone allowed to avoid this drawback. Finally, the proposed mechanism was successfully applied to the design of a novel, easy and high purity procedure for the synthesis of the acetylated penicilloic acid, known related substance of piperacillin.

New isoxazolidinone and 3,4-dehydro-ß-proline derivatives as antibacterial agents and MAO-inhibitors: A complex balance between two activities.

Among the different classes of antibiotics, oxazolidinone derivatives represent important drugs, since their unique mechanism of action overcomes commonly diffused multidrug-resistant bacteria. Anyway, the structural similarity of these molecules to monoamino oxidase (MAO) inhibitors, like toloxatone and blefoxatone, induces in many cases loss of selectivity as a major concern. A small library of compounds based on isoxazolidinone and dehydro-ß-proline scaffold was designed with the aim to obtain antibacterial agents, evaluating at the same time the potential effects of structural features on MAO inhibitory behaviour. The structural modification introduced in the backbone, starting from Linezolid model, lead to a significant loss in antibiotic activity, while a promising inhibitory effect could be observed on monoamino oxidases. These interesting results are also in agreement with docking experiments suggesting a good binding pose of the synthesized compounds into the pocket of the oxidase enzymes, in particular of MAO-B.

Dehydro-ß-proline Containing α4ß1 Integrin Antagonists: Stereochemical Recognition in Ligand-Receptor Interplay.

A novel class of dehydro-ß-proline-containing peptidomimetics, designed to be effective as α4ß1 integrin ligands, has been developed on the basis of the fundamental requirements for the interactions of these transmembrane receptors with bioactive ligands. Dehydro-ß-proline ring has been synthesized through an original pathway, involving ring closing metathesis of a diallylamino derivative. The synthesized products showed to be effective and selective as α4ß1 integrin antagonists and displayed IC50 values in the nanomolar range in cell adhesion inhibition assays and in VCAM-1-induced phosphorylation of extracellular-signal-regulated kinases. Significant activity was observed also toward the homologous integrin α4ß7, while they did not display any activity toward selected members of ß1, ß2, and ß3 families. A strong dependence on the stereochemistry of the heterocyclic central core could be observed. The great importance of α4ß1 integrin in chronic inflammatory and autoimmune diseases suggests a possible exploitation of these ligands as lead compounds for therapeutic tools development.

Toward the development of dual-targeted glyceraldehyde-3-phosphate dehydrogenase/trypanothione reductase inhibitors against Trypanosoma brucei and Trypanosoma cruzi.

A significant improvement in the treatment of trypanosomiases has been achieved with the recent development of nifurtimox-eflornithine combination therapy (NECT). As an alternative to drug combinations and as a means to overcome most of the antitrypanosomatid drug discovery challenges, a multitarget drug design strategy has been envisaged. To begin testing this hypothesis, we designed and developed a series of quinone-coumarin hybrids against glyceraldehyde-3-phosphate dehydrogenase/trypanothione reductase (GAPDH/TR). These enzymes belong to metabolic pathways that are vital to Trypanosoma brucei and Trypanosoma cruzi, and have thus been considered promising drug targets. The synthesized molecules were characterized for their dual-target antitrypanosomal profile, both in enzyme assays and in in vitro parasite cultures. The merged derivative 2-{[3-(3-dimethylaminopropoxy)-2-oxo-2H-chromen-7-yl]oxy}anthracene-1,4-dione (10) showed an IC50 value of 5.4 µM against TbGAPDH and a concomitant Ki value of 2.32 µM against TcTR. Notably, 2-{4-[6-(2-dimethylaminoethoxy)-2-oxo-2H-chromen-3-yl]phenoxy}anthracene-1,4-dione (compound 6) displayed a remarkable EC50 value for T.brucei parasites (0.026 µM) combined with a very low cytotoxicity toward mammalian L6 cells (7.95 µM). This promising low toxicity of compound 6 might be at least partially due to the fact that it does not interfere with human glutathione reductase.

Modulation of αvß3- and α5ß1-integrin-mediated adhesion by dehydro-ß-amino acids containing peptidomimetics.

A novel class of low molecular weight ligands of αvß3 and α5ß1 integrins, that possess a dehydro-ß-amino acid as conformationally constrained core, linked to the pharmacophoric moieties mimicking the RGD recognition sequence, have been synthesized through a very simple protocol. Cell adhesion assays and integrin-mediated signaling activation experiments suggested a good affinity of these compounds toward both integrin receptors. Moreover, further elongation with two glycine units allowed to obtain an excellent dual inhibitor. Structural models for αvß3 integrin-ligand binding confirmed that the dehydro-ß-amino derivatives are able to act as an electrostatic clamp by establishing several stabilizing interactions with the receptor.

Development of isoxazoline-containing peptidomimetics as dual αvß3 and α5ß1 integrin ligands.

Isoxazoline-containing peptidomimetics, designed to be effective α(v)ß(3) and α(5)ß(1) integrin ligands, were synthesized through an original procedure involving N,O-bis(trimethylsilyl)hydroxyamine conjugate addition to alkylidene acetoacetates, followed by intramolecular hemiketalization. To mimic the RGD recognition sequence, basic and acidic terminal appendages were introduced, and the final products were tested in cell adhesion inhibition assays. All the synthesized compounds proved to be excellent ligands for both integrin receptors, and a strong influence on intracellular signaling and phosphorylation pathways was demonstrated by evaluation of fibronectin-induced phosphorylation of ERK. The molecular basis of the observed inhibitory activity was suggested on the results of docking experiments.

A straightforward route to enantiopure 2-substituted-3,4-dehydro-ß-proline via ring closing metathesis.

The synthesis of unusual cyclic amino acids, that may be envisaged as proline analogs, is an area of great interest for their potential applications as scaffolds for the design of bioactive peptidomimetics or units for the creation of novel foldamers. We have carried out the preparation of cyclic dehydro-ß-amino acids starting from allylic carbonates via a two-step allylic amination/ring closing metathesis (RCM) protocol. The introduction of the allylamino moiety has been carried out either without a catalyst, through an S(N)2' reaction, or in the presence of iridium complexes. The backbone of the allylamino intermediates contains two unsaturations, thus suggesting that RCM could be a valuable tool for the preparation of dihydropyrrole scaffolds. A similar reaction has been already reported in the literature for racemic aromatic-substituted substrates, but no examples of enantiopure derivatives bearing aliphatic chains have been reported. The reaction was optimized by testing different Grubbs' catalysts and carbamate nitrogen protecting groups. Moreover, in view of a future application of these dehydro-ß-amino acids as central core of peptidomimetics, the malonate chain was also used to protect nitrogen prior to RCM.