Novel pi-expanded radialene macrocycles with inner cavity

[structure: see text] Polyenyne macrocycles with pi-extended [9]- and [12]radialene frameworks have been synthesized. These radialenes exhibit restricted rotation of the aromatic rings, and the D3- and D4-symmetric structures in solutions have been determined by dynamic NMR. The macrocyclic radialenes bear small to medium inner cavities, and the small cavity of the pi-extended [9]radialene can incorporate a silver cation.     

Determination of picomolar beryllium levels in seawater with inductively coupled plasma mass spectrometry following silica-gel preconcentration

A robust and rapid method for the determination of natural levels of beryllium (Be) in seawater was developed to facilitate mapping Be concentrations in the ocean. A solid-phase extraction method using a silica gel column was applied for preconcentration and purification of Be in seawater prior to determination of Be concentrations with inductively coupled plasma mass spectrometry (ICP-MS). Be was quantitatively adsorbed onto silica gel from solutions with pH values ranging from 6.3 to 9, including natural seawater. The chelating agent ethylenediamine tetraacetic acid was used to remove other ions in the seawater matrix (Na, Mg, and Ca) that interfere with the ICP-MS analysis. The reproducibility of the method was 3% based on triplicate analyses of natural seawater samples, and the detection limit was 0.4 pmol kg⁻¹ for 250 mL of seawater, which is sufficient for the analysis of seawater in the open ocean. The method was then used to determine the vertical profile of Be in the eastern North Pacific Ocean, which was found to be a recycled-type profile in which the Be concentration increased with depth from the surface (7.2 pmol kg⁻¹ at <200 m) to deep water (29.2 pmol kg⁻¹ from 3500 m to the bottom).     

Internal amide-triggered cycloaromatization of maduropeptin-like nine-membered enediyne

In the Masamune-Bergman cyclization of a nine-membered non-conjugated enediyne with an internal, maduropeptin-like nucleophile, the exocyclic alkene migrated to form the nine-membered conjugated enediyne, triggered by the intramolecular addition of the amide group; final aromatized products showed up to 85% yield.     

Structural analysis of glycosphingolipid analogues obtained by the saccharide primer method using CE‐ESI‐MS

A glycosphingolipid analogue (12‐azidododecyl β‐lactoside) as a saccharide primer has been shown to be useful for the synthesis of oligosaccharide libraries by mammalian cells. In the present study, CE‐ESI‐MS was employed to elucidate the structure of glycosphingolipid analogues derived from 12‐azidododecyl β‐lactoside (Lac‐C12N3) by mammalian cells. MDCK cells and COLO201 cells were cultured with Lac‐C12N3, and the glycosylated products secreted into the medium were collected and separated into acidic and neutral products by column chromatography. The acidic products could be directly analyzed by CE‐ESI‐MS, while the neutral products were converted to anionic derivatives via a reaction with propiolic acid. With this method, it was possible to analyze both acidic and neutral products glycosylated by MDCK cells and COLO201 cells at high sensitivity.     

An efficient synthesis of 4‐alkoxy‐5,6‐dihydro‐furo(and ‐thieno)[2,3‐d]pyrimidines using zinc chloride/triethylamine reagent system

The one‐pot synthesis of 4‐alkoxy‐5,6‐dihydro‐furo(and ‐thieno)[2,3‐d]pyrimidines is described. The reactions of 2‐benzamido‐4,5‐dihydro‐3‐furan(and ‐3‐thiophene)carbonitriles 1a‐d and 2a‐c with ethanol and/or methanol in the presence of zinc chloride and triethylamine gave the corresponding 4‐alkoxy‐5,6‐dihydro‐furo(and ‐thieno)[2,3‐d]pyrimidines 3a‐d , 4a‐d , 5a‐c and 6a‐c .     

Flow visualization and scanning PIV measurement of three-dimensional structure in near field of strongly buoyant jet

Abstract  

The near-field structure of strongly buoyant jet issuing from a square nozzle at low Froude and Reynolds numbers is studied by using LIF flow visualization and time-resolved scanning PIV. These experimental techniques allow the visualization of unsteady three-dimensional flow phenomenon occurring in the near-field of strongly buoyant jet. It is found that the buoyant jet is unstable to the positive buoyancy forces, which promote the inflow motion near the nozzle exit. The surrounding low temperature fluid moves into the nozzle inside along the nozzle corner and mixes with the high temperature fluid deep into the nozzle. Then, the flow pattern inside the nozzle becomes highly complex to promote the laminar to turbulent transition of the jet. The statistical flow characteristics of the strongly buoyant jet are evaluated from the scanning PIV measurement, and the result indicates the presence of axisymmetric distributions of mean flow and velocity fluctuations in the circle of diameter equal to the square side of the nozzle.     

Synthesis of 5,6‐dihydrothieno(and furo)pyrimidines bearing an active methine group at the 4‐position

The reactions of 2‐benzamido‐4,5‐dihydro‐3‐thiophene(and ‐3‐furan)carbonitriles ( 1a‐c and 4a‐c ) with ethyl acetoacetate in the presence of tin(IV) chloride and triethylamine provided the corresponding ethyl 2‐(5,6‐dihydro‐2‐phenylthieno(and furo)[2,3‐d]pyrimidin‐4‐yl)‐3‐oxobutanoates ( 2a‐c and 9a‐c ). Similarly, compounds 1a‐c and 4a‐c reacted with dialkyl malonates to give the corresponding dialkyl(5,6‐dihydro‐2‐phenylthieno(and furo)[2,3‐d]pyrimidin‐4‐yl)propanedioates ( 5a‐c, 6a‐c, 10a‐c and 11a‐c ).