Synthesis of 3-Amino-4-Substituted Monocyclic ß-Lactams—Important Structural Motifs in Medicinal Chemistry

Monocyclic ß-lactams (azetidin-2-ones) exhibit a wide range of biological activities, the most important of which are antibacterial, anticancer, and cholesterol absorption inhibitory activities. The synthesis of decorated monocyclic ß-lactams is challenging because their ring is highly constrained and consequently reactive, which is also an important determinant of their biological activity. We present the optimized synthesis of orthogonally protected 3-amino-4-substituted monocyclic ß-lactams. Among several possible synthetic approaches, Staudinger cycloaddition proved to be the most promising method for initial ring formation, yielding monocyclic ß-lactams with different substituents at the C-4 position, a phthalimido-protected 3-amino group, and a (dimethoxy)benzyl protected ring nitrogen. Challenging deprotection methods were then investigated. Oxidative cleavage with cerium ammonium nitrate and ammonia-free Birch reduction was found to be most effective for selective removal of ring nitrogen protection. Hydrazine hydrate was used for deprotection of the phthalimido group, and the procedure had to be modified by the addition of HCl in the case of aromatic substituents at the C-4 position. The presented methods and the synthesized 3-amino-4-substituted monocyclic ß-lactam derivatives are an important step toward new ß-lactams with potential pharmacological activities.

4-Amino-2-(p-tolyl)-7H-chromeno[5,6-d]oxazol-7-one

The new 4-amino-2-(p-tolyl)-7H-chromeno[5,6-d]oxazol-7-one was successfully prepared through the Au/TiO2-catalyzed NaBH4 activation and chemoselective reduction of the new 4-nitro-2-(p-tolyl)-7H-chromeno[5,6-d]oxazol-7-one. The latter was synthesized by the one-pot tandem reactions of 6-hydroxy-5,7-dinitrocoumarin with p-tolylmethanol under Au/TiO2 catalysis. The dinitrocoumarin was obtained by the nitration of 6-hydroxycoumarin with cerium ammonium nitrate (CAN). The structure of the synthesized compounds was confirmed by FT-IR, HR-MS, 1H-NMR and 13C-NMR analysis. Preliminary biological tests show low anti-lipid peroxidation activity for the title compound.

An astonishing simple cerium-based chemosensor for fluorescent selective phosphate detection in aquaeous medium

<div><div><div><p>Phosphate ions are socially important chemicals. They are involved in crucial processes such as for example in medicine or agriculture. However, their sensing with a chemosensor is ardous due to their chemical properties. In this context, a remarkable chemosensor would reveal an outstanding affinity, a high selectivity and a low detection limit in favor of an analyte. This has long been addressed in the past by chemists in synthesizing com- plex chemical architectures as receptors but with questionable successes. Astonishingly, here, for phosphate detection, we address this problem profiting by a simple fluorescent indicator displacement assay (FID) with only commercially available chemicals. We used cerium ammonium nitrate (CAN) combined with a fluorophore to probe phosphate ions in aqueous mediums. The inorganic complex detects phosphate ions in low millimolar concentrations either spectrophotometrically or with the naked-eye with high selectivity and affinity over other anions. To our knowledge, this is the first description of a simple sensitive, selective and high affinity cerium-based chemosensor for the fluorescent selective naked-eye detection of phosphate in aqueous medium. It proved useful for the detection of phosphate in Coca-Cola©.</p></div></div></div>

Graft Copolymerization of Cinnamic Acid to Cassava Starch and its Viscosity Measurements

In this study, the modification of starch was conducted through graft copolymerization of cinnamic acid to result in starch-g-poly(cinnamic acid). The cinnamic acid polymerization was carried out via radical polymerization using cerium ammonium nitrate (CAN) as an initiator. The viscosity of the graft copolymer 10000 ppm dissolved in 16% NaOH solution was measured at a temperature range of 25-75 °C. The results showed that the higher the temperature the lower the viscosity. The activation energy of viscous flow for the copolymer was 18.4 kJ.mol-1. The viscosity values of the copolymer solutions were also measured in saline solutions with NaCl contents of 3−20%(w/v). For the measurements in these saline solutions, the highest viscosity was 3.39 cP at room temperature for the copolymer solution containing 5%(w/v) NaCl.

Polymer Grafting on Cellulose Nanocrystals Initiated by Ceric Ammonium Nitrate: Is It Feasible under Acid-Free Conditions?

It is of great significance to tailor the physicochemical properties of cellulose nanocrystals (CNCs) for broadening their application fields. Grafting polymerization initiated by cerium ammonium nitrate (CAN) in aqueous medium...

An astonishing simple cerium-based chemosensor for fluorescent selective phosphate detection in aquaeous medium

<div><div><div><p>Phosphate ions are socially important chemicals. They are involved in crucial processes such as for example in medicine or agriculture. However, their sensing with a chemosensor is ardous due to their chemical properties. In this context, a remarkable chemosensor would reveal an outstanding affinity, a high selectivity and a low detection limit in favor of an analyte. This has long been addressed in the past by chemists in synthesizing com- plex chemical architectures as receptors but with questionable successes. Astonishingly, here, for phosphate detection, we address this problem profiting by a simple fluorescent indicator displacement assay (FID) with only commercially available chemicals. We used cerium ammonium nitrate (CAN) combined with a fluorophore to probe phosphate ions in aqueous mediums. The inorganic complex detects phosphate ions in low millimolar concentrations either spectrophotometrically or with the naked-eye with high selectivity and affinity over other anions. To our knowledge, this is the first description of a simple sensitive, selective and high affinity cerium-based chemosensor for the fluorescent selective naked-eye detection of phosphate in aqueous medium. It proved useful for the detection of phosphate in Coca-Cola©.</p></div></div></div>

An astonishing simple cerium-based chemosensor for fluorescent selective phosphate detection in aquaeous medium

<div><div><div><p>Phosphate ions are socially important chemicals. They are involved in crucial processes such as for example in medicine or agriculture. However, their sensing with a chemosensor is ardous due to their chemical properties. In this context, a remarkable chemosensor would reveal an outstanding affinity, a high selectivity and a low detection limit in favor of an analyte. This has long been addressed in the past by chemists in synthesizing com- plex chemical architectures as receptors but with questionable successes. Astonishingly, here, for phosphate detection, we address this problem profiting by a simple fluorescent indicator displacement assay (FID) with only commercially available chemicals. We used cerium ammonium nitrate (CAN) combined with a fluorophore to probe phosphate ions in aqueous mediums. The inorganic complex detects phosphate ions in low millimolar concentrations either spectrophotometrically or with the naked-eye with high selectivity and affinity over other anions. To our knowledge, this is the first description of a simple sensitive, selective and high affinity cerium-based chemosensor for the fluorescent selective naked-eye detection of phosphate in aqueous medium. It proved useful for the detection of phosphate in Coca-Cola©.</p></div></div></div>

Ni-catalyzed asymmetric hydrogenation of N-aryl imino esters for the efficient synthesis of chiral α-aryl glycines

Chiral α-aryl glycines play a key role in the preparation of some bioactive products, however, their catalytic asymmetric synthesis is far from being satisfactory. Herein, we report an efficient nickel-catalyzed asymmetric hydrogenation of N-aryl imino esters, affording chiral α-aryl glycines in high yields and enantioselectivities (up to 98% ee). The hydrogenation can be conducted on a gram scale with a substrate/catalyst ratio of up to 2000. The obtained chiral N-p-methoxyphenyl α-aryl glycine derivatives are not only directly useful chiral secondary amino acid esters but can also be easily deprotected by treatment with cerium ammonium nitrate for further transformations to several widely used molecules including drug intermediates and chiral ligands. Formation of a chiral Ni-H species in hydrogenation is detected by 1H NMR. Computational results indicate that the stereo selection is determined during the approach of the substrate to the catalyst.