Development of sheath‐flow probe electrospray ionization (SF‐PESI)

Probe electrospray ionization (PESI) uses a sharp solid needle as electrospray emitter. This method was found to be applicable to the analysis of real‐world samples with high concentrations of salts and detergents without sample pretreatment. Since PESI is only applicable to wet samples but not to dry samples, sheath‐flow PESI (SF‐PESI) has been developed. The metal needle was inserted into the fine plastic capillary with a protrusion of 0.1–0.2 mm from the capillary terminus. The solvent was supplied continuously through the capillary. At the lowest position of the probe, solvent flowing out from the capillary makes the sample wet and extracts the analytes from the surface. The extracted analytes were electrosprayed at the highest position of the needle. SF‐PESI was successfully applied to samples such as narcotics, tablets, bill, fruits, potatoes, etc. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthetic studies toward potent cytostatic macrolide rhizopodin: stereoselective synthesis of the C16-C28 fragment

A stereoselective synthesis of the C16-C28 fragment of cytostatic C₂-symmetric macrolide rhizopodin is described. Enantioselective addition of a chiral thiazolidinethione derived titanium enolate to acetal, Evans’ aldol reaction, Horner-Wadsworth-Emmons reaction, and Mukaiyama aldol reaction were applied as key steps.     

Total synthesis of (+)-mupirocin H from D-glucose

Enantioselective total synthesis of mupirocin H is accomplished starting from D-glucose featuring strategic application of D-glucose derived chirality, diastereoselective Still-Barrish hydroboration, and further elaboration of carbon chain to furnish a phenyltetrazolyl sulfone intermediate, which on coupling with (2S,3S)-2-methyl-3-(triisopropylsilyloxy)butanal under Julia-Kocienski olefination conditions gave an advanced E-olefinic intermediate selectively. The E-olefin was transformed to the 4-hydroxynitrile, a prefinal substrate, which on acid-catalyzed oxidative lactonization furnished the target molecule mupirocin H in 19 steps from known compound 6 (longest linear sequence) with an overall yield of 4.96%.     

Reactivity of nickel(II) and copper(II) complexes of a β-aminohydrazone ligand with pyridine-2-aldehyde: macrocyclization vs unprecedented pyrazole ring synthesis via C-C bond-forming reaction

The synthesis and characterization of a mononuclear nickel(II) complex [Ni(L(2))](ClO(4))(2) (1) and an analogous mononuclear copper(II) complex [Cu(L(2))](ClO(4))(2) (2) of a 15-membered azamacrocycle (L(2) = 3-(2-pyridyl)-6,8,8,13,13,15-hexamethyl-1,2,4,5,9,12-hexaazacyclopentadeca-5,15-diene) are reported. The macrocyclic ligand is formed during the reaction of 4,4,9,9-tetramethyl-5,8-diazadodecane-2,11-dione dihydrazone (L(1)) with pyridine-2-aldehyde (PyCHO) templated by metal ions. The X-ray crystal structure of 1 exhibits a distorted square-pyramidal coordination geometry, where the metal ion sits in the macrocyclic cavity and the pendant pyridine group of L(2) occupies the axial position. While 1 is stable in the presence of an excess of PyCHO, 2 reacts further with copper(II) salt and PyCHO to form a mononuclear copper(I) complex, [Cu(H(2)L(3))](ClO(4))(3) (3). The structure of the complex cation of 3 reveals a distorted tetrahedral coordination geometry at the copper center with a pseudo 2-fold screw axis. A two-dimensional (2D) polymeric copper(II) complex, {[Cu(2)(L(4))(2)](ClO(4))(2)}(n) (4) is obtained by reacting complex 2 (or [Ni(L(1))](ClO(4))(2)) with copper(II) perchlorate and pyridine-2-aldehyde in a methanol-water solvent mixture. Complex 4 is also obtained by treating 3 with copper(II) perchlorate and pyridine-2-aldehyde in the presence of a base. The X-ray structural analysis of 4 confirms the formation of a pyrazolate bridged dimeric copper(II) complex. The extended structure in the solid state of 4 revealed the formation of a 2D coordination polymer with the dimeric core as the repeating unit. The ligand (HL(4)) in 4 is a 3,4,5-trisubstituted pyrazole ring formed in situ via C-C bond formation and represents an unprecedented transformation reaction.     

Sequential and Exhaustive Ionization of Analytes with Different Surface Activity by Probe Electrospray Ionization

The probe electrospray ionization (PESI) is an ESI-based ionization technique that generates electrospray from the tip of a solid metal needle. In this work, mass spectra for the single-shot PESI were measured as a function of time for a mixture of several analytes with different surface activity values. It was found that the analytes were elecrosprayed in the order of their surface activity. For example, detergent and protein were detected separately and respectively at the first and last stages of electrospray, for a mixed sample of 10^–3 M Triton X100 and 10^–5 M cytochrome c. For human breast cancer tissue, at first proteins such as α and β chains of hemoglobin, were observed as the dominant ions, but just before the liquid droplet on the needle was depleted only lipids were observed, meaning that PESI has the advantage of the suppression effect with analytes being detected separately in the order of their surface activity values.     

Inhomogeneous Bulk Viscous Fluid Universe with Electromagnetic Field and Variable ∧-Term

Cylindrically symmetric inhomogeneous cosmological model for bulk viscous fluid distribution with electro- magnetic field is obtained. The source of the magnetic field is due to an electric current produced along the z-axis. F12 is the non-vanishing component of electromagnetic field tensor. To get the deterministic solution, it has been assumed that the expansion 0 in the model is proportional to the shear σ. The values of cosmological constant for these models are found to be small and positive at late time, which are consistent with the results from recent supernovae Ia observations. Physical and geometric aspects of the models are also discussed in presence and absence of magnetic field.     

N-Rich,Polyphenolic Porous Organic Polymer and Its In Vitro Anticancer Activity on Colorectal Cancer

N-rich organic materials bearing polyphenolic moieties in their building networks and nanoscale porosities are very demanding in the context of designing efficient biomaterials or drug carriers for the cancer treatment. Here, we report the synthesis of a new triazine-based secondary-amine- and imine-linked polyphenolic porous organic polymer material TrzTFPPOP and explored its potential for in vitro anticancer activity on the human colorectal carcinoma (HCT 116) cell line. This functionalized (-OH, -NH-, -C=N-) organic material displayed an exceptionally high BET surface area of 2140 m² g⁻¹ along with hierarchical porosity (micropores and mesopores), and it induced apoptotic changes leading to high efficiency in colon cancer cell destruction via p53-regulated DNA damage pathway. The IC30, IC50, and IC70 values obtained from the MTT assay are 1.24, 3.25, and 5.25 μg/mL, respectively.     

A New Compound for Sequential Sensing of Picric Acid and Aliphatic Amines: Physicochemical Details and Construction of Molecular Logic Gates

Picric acid (PA) at low concentration is a serious water pollutant. Alongside, aliphatic amines (AAs) add to the queue to pollute surface water. Plenty of reports are available to sense PA with an ultralow limit of detection (LOD). However, only a handful of works are testified to detect AAs. A new fluorescent donor-acceptor compound has been synthesized with inherent intramolecular charge transfer (ICT) character that enables selective and sensitive colorimetric quantitative detection of PA and AAs with low LODs in non-aqueous as well as aqueous solutions. The synthesized compound is based on a hemicyanine skeleton containing two pyridenylmethylamino groups at the donor and a benzothiazole moiety at the acceptor ends. The detailed mechanisms and reaction dynamics are explained spectroscopically along with computational support. The fluorescence property of the detecting compound changes due to protonation of its pyridinyl centers by PA leading to quenching of fluorescence and subsequently de-protonation by AAs to revive the signal. We have further designed logic circuits from the acquired optical responses by sequential interactions.