Recognition of aromatic compounds by π pocket within a cage-shaped borate catalyst

Taking shape: the ability of a Lewis acid catalyst to distinguish between aromatic and aliphatic hydrocarbon moieties was accomplished by using cage-shaped borate catalysts B(OC(6)H(3)Aryl)(3)CH having a π pocket derived from aryl substituents surrounding the boron center. The catalyst predominantly activated aromatic aldehydes over aliphatic ones for reaction.     

Application of high‐resolution ESI and MALDI mass spectrometry to metabolite profiling of small interfering RNA duplex

We investigated the application of a high‐resolution Orbitrap mass spectrometer equipped with an electrospray ionization (ESI) source and a matrix‐assisted laser desorption/ionization‐time‐of‐flight (MALDI‐TOF) mass spectrometer to the metabolite profiling of a model small interfering RNA (siRNA) duplex TSR#34 and compared their functions and capabilities. TSR#34 duplex was incubated in human serum in vitro, and the duplex and its metabolites were then purified by ion exchange chromatography in order to remove the biological matrices. The fraction containing the siRNA duplex and its metabolites was collected and desalted and then subjected to high‐performance liquid chromatography (HPLC) equipped with a reversed phase column. The siRNA and its metabolites were separated into single strands by elevated chromatographic temperature and analyzed using the ESI‐Orbitrap or the MALDI‐TOF mass spectrometer. Using this method, the 5' and/or 3' truncated metabolites of each strand were detected in the human serum samples. The ESI‐Orbitrap mass spectrometer enabled differentiation between two possible RNA‐based sequences, a monoisotopic molecular mass difference which was less than 2 Da, with an intrinsic mass resolving power. In‐source decay (ISD) analysis using a MALDI‐TOF mass spectrometer allowed the sequencing of the RNA metabolite with characteristic fragment ions, using 2,4‐dihydroxyacetophenone (2,4‐DHAP) as a matrix. The ESI‐Orbitrap mass spectrometer provided the highest mass accuracy and the benefit of on‐line coupling with HPLC for metabolite profiling. Meanwhile, the MALDI‐TOF mass spectrometer, in combination with 2,4‐DHAP, has the potential for the sequencing of RNA by ISD analysis. The combined use of these methods will be beneficial to characterize the metabolites of therapeutic siRNA compounds. Copyright © 2012 John Wiley & Sons, Ltd.     

An efficient and selective conversion of sorbitol in ionic liquids: Use of ion exchange resin as a solid acid catalyst

Sorbitol was readily converted by heating in hydrophobic ionic liquids by the presence of ion exchange resins. Chemoseletivity of the dehydration depended on the choice of ion exchange resin; Nafion selectively produced isosorbide while Amberlite gave 1,5-anhydrosorbitol along with unreacted sorbitol. Ionic liquids used in the reaction were readily recovered by simple extraction procedure. With these procedures, we succeeded to prepare isosorbide in pure form, not contaminated with either ionic liquids or acid catalyst, by simple experimental procedure.     

FOURIER TRANSFORM INFRARED SPECTRAL STUDIES ON THE SCHIFF BASE MODE OF ALL-trans BACTERIORHODOPSIN and ITS PHOTOINTERMEDIATES,K and L*

Abstract– Difference Fourier transform infrared spectra were recorded for bacteriorhodopsin upon irradiation at 230, 170 or 77 K, which gave, respectively, the spectrum of the M, L or K intermediate minus unphotolyzed all-trans bacteriorhodopsin (denoted as BR). By replacement of the Schiff base nitrogen with ¹⁵N, or of either its hydrogen at N or C₁₅ with deuterium, the vibrational bands related to the Schiff base were identified and the isotope-shifts evaluated for BR, K and L. The 1348 cm^?l band of BR and K and the 1400 cm^?1 band of L were sensitive to each of these isotope substitutions. The 1254 cm^?1 band of BR, the 1245 cm^?1 band of K and the 1301 cm^?1 band of L were sensitive to either N- or C₁₅-deuteration but not to ¹⁵N-substitution. The N—D in-plane bending vibration of K and L appeared at 969 and 997 cm^?1, respectively, upon substitution with D₂O. All the results show that L is larger in frequencies related to the N—H in-plane bending vibration than K or BR and suggest that L has the strongest interaction with the protein. Among the bands containing an N—H bending vibration, the 1348 cm^?1 band of K was more intense than the corresponding band of L at 1400 cm^?1. The C₁₅-deuteration-induced upshift of the 1245 cm^?1 band of K was unobservable for the 1301 cm^?1 band of L. Such differences between L and K might be brought about by a distortion in the retinal moiety close to the protonated Schiff base of the 13-cis chromophore.     

Structural Elucidation of an Elicitor-Active Oligosaccharide,LN-3, Prepared from Algal Laminaran

Abstract

The primary structure of an elicitor-active oligosaccharide, LN-3, prepared from partially hydrolyzed algal laminaran was determined by means of the analyses of glycosyl-linkage, fragments by acetolysis, and glycosyl-sequence. The elicitor-active oligosaccharide, LN-3, is a pyridylaminated hepta-β-d-glucoside which was shown to have the following linear structure: β-d-Glcp(1→6)-β-d-Glcp(1→3)-β-d-Glcp(1→3)-β-d-Glcp(1→3)-β-d-Glcp(1→6)-β-d-Glcp(1→3)-Glc-PA.     

Rapid and high-resolution analysis of geometric polyprenol homologues by connected octadecylsilylated monolithic silica columns in high-performance liquid chromatography

A Chromolith Performance octadecylsilyl (ODS) monolithic silica column (Merck) was compared with a conventional microparticulate ODS-bonded silica column in the high-performance liquid chromatography separation of natural polyprenols. A system comprising two connected monolithic columns afforded an equivalent separation at half the analysis time of the conventional method. Furthermore, ten connected columns achieved a tremendously high-resolution separation, in which the complicated series of homologous polyprenols with geometric isomerism were fully separated.     

Preparation of (Z)-1-fluoro-1-alkenyl carboxylates,carbonates and carbamates through chromium mediated transformation of dibromofluoromethylcarbinyl esters and the reactivity as double acyl group donors

CrCl₂/Mn-mediated transformation of various dibromofluoromethylcarbinyl esters including carboxylates, carbonates and carbamates provided 1-fluoro-1-alkenyl esters via [2,3]-sigmatropic rearrangement of ester group. Reaction proceeded by using CrCl₂/Mn system under mild conditions (in THF at room temperature) to give 1-fluoro-1-alkenyl esters in good yield with an excellent Z selective manner. 1-Fluoro-1-alkenyl ester thus obtained acts as a double acyl donor in the reaction with necleophiles such as amine, thiol, alcohol as well as bifunctional necleophiles such as ethylene diamine derivative.