Base‐Promoted Coupling of Carbon Dioxide,Amines, and N‐Tosylhydrazones: A Novel and Versatile Approach to Carbamates

A base‐promoted three‐component coupling of carbon dioxide, amines, and N‐tosylhydrazones has been developed. The reaction is suggested to proceed via a carbocation intermediate and constitutes an efficient and versatile approach for the synthesis of a wide range of organic carbamates. The advantages of this method include the use of readily available substrates, excellent functional group tolerance, wide substrate scope, and a facile work‐up procedure.     

Metal‐Free Dehydrogenative Diels–Alder Reactions of 2‐Methyl‐3‐Alkylindoles with Dienophiles: Rapid Access to Tetrahydrocarbazoles,Carbazoles, and Heteroacenes

An unprecedented strategy for in situ generation of indole‐based ortho‐quinodimethanes (oQDMs) from 2‐methyl‐3‐alkylmethylindoles by either a metal‐free DDQ‐ or BQ‐mediated dehydrogenative process was developed. These oQDMs were trapped by electron‐deficient dienophiles to provide a facile approach to synthetically valuable tetrahydrocarbazoles, carbazoles, and hetereoacenes. The salient features of this transformation include direct C(sp³) H bond functionalizations, readily available starting materials, metal‐free conditions, high efficiency, operational simplicity, and ease of scale‐up.     

Separation and Characterization of Unknown Impurities in Amikacin Sulfate by HPLC–MS n

Nine impurities in amikacin sulfate made in China were separated and identified by HPLC–MSⁿ for the further improvement of official monographs in pharmacopoeias. The mass fragmentation patterns and structural assignment of these impurities were studied. The column was Acchrom Click XIon (250 × 4.6 mm, 5 μm). The mobile phase was 250 m mol L⁻¹ ammonium formate and 1.4 % formic acid aqueous solution–acetonitrile–water (30:48:22). In positive mode, full scan LC–MS was first performed in order to obtain the m/z value of the protonated molecules, LC–MS–MS was then carried out on the compounds of interest on AB SCIEX 4000 Q TRAP™ composite triple quadrupole/linear ion trap tandem mass spectrometer. The complete fragmentation patterns of nine impurities were studied and used to obtain information about the structure of these impurities. The structures of nine impurities in amikacin sulfate were deduced based on the HPLC–MSⁿ data, in which three impurities were novel impurities. Three novel impurities were 1-N-(l-4-amino-2-hydroxybutyryl) derivative of 4-O-(6-AG)DS, 1-N-(l-4-amino-2-hydroxybutyryl) derivative of 6-O-(3-AG)DS and 1-N-(l-4-amino-2-hydroxybutyryl) derivative of kanamycin D.

     

Two New Triterpene Saponins from the Seed Residue of Hippophae rhamnoides L.

Two new triterpene saponins, named hippophosides E and F ( 1 and 2 , resp.), together with two known compounds, were isolated from the seed residue of Hippophae rhamnoides L. Their structures were elucidated on the basis of chemical and spectral analysis, including 1D‐ and 2D‐NMR and HR‐MS experiments, and by comparison with literature data.     

Poly(o-phenylenediamine) nanosphere-conjugated capture antibody immobilized on a glassy carbon electrode for electrochemical immunoassay of carcinoembryonic antigen

We report on a new electrochemical immunosensor for the carcinoembryonic antigen (CEA; a model analyte). First, poly(o-phenylenediamine) nanospheres (PPDNSs) were synthesized by using a wet-chemistry method. The nanospheres were utilized as the support for immobilizing horseradish peroxidase-labeled polyclonal rabbit anti-human CEA antibody (HRP-anti-CEA) on a pretreated glassy carbon electrode (GCE) using glutaraldehyde as a crosslinker. In the presence of target CEA, an antigen-antibody immunocomplex formed on the electrode. This results in a partial inhibition of the active center of HRP and decreases the activity of HRP in terms of H₂O₂ reduction. The performance and factors influencing the performance of the immunoelectrode were studied. Under optimal conditions, the reduction current obtained from the anti-CEA-conjugated HRP (best at a working voltage of −265 mV vs. Ag/AgCl) is proportional to the CEA concentration in the 0.01 to 60 ng mL⁻¹ range, with a detection limit of 3.2 pg mL⁻¹. Non-specific adsorption was not observed. Relative standard deviations for intra-assay and inter-assay are <8.3 % and <9.7 %, respectively. The method was applied to the analysis of nine human serum samples, and a good relationship was found between the electrochemical immunoassay and the commercialized ELISA kit for human CEA.

A new electrochemical immunosensor based on poly(o-phenylenediamine) nanospheres was developed for the rapid detection of carcinoembryonic antigen via the inhibition of enzymatic activity.

     

N‐Arylation of Heterocycles Promoted by Cyclen Derivatives

An efficient copper‐catalyzed N‐arylation reactions of imidazole, indole, and triazole with aryl or heteroaryl halides using cyclen derivatives as efficient organic base and ligand at moderate temperature have been investigated. The cross‐couplings proceed smoothly with good to excellent yields.