Unexpected linear ion trap collision‐induced dissociation and Fourier transform ion cyclotron resonance infrared multi‐photon dissociation fragmentation of a hydrated C‐glycoside of 5‐fluorouridine formed by the action of the pseudouridine synthases RluA and TruB

As part of the investigation of the pseudouridine synthases, 5‐fluorouridine in RNA was employed as a mechanistic probe. The hydrated, rearranged product of 5‐fluorouridine was isolated as part of a dinucleotide and found to undergo unusual fragmentation during mass spectrometry, with the facile loss of HNCO from the product pyrimidine ring favored over phosphodiester bond rupture. Although the loss of HNCO from uridine and pseudouridine is well established, the pericyclic process leading to their fragmentation cannot operate with the saturated pyrimidine ring in the product of 5‐fluorouridine. Based on the MSⁿ results and calculations reported here, a new mechanism relying on the peculiar disposition of the functional groups of the product pyrimidine ring is proposed to account for the unusually facile fragmentation. Copyright © 2011 John Wiley & Sons, Ltd.     

A microwave-assisted nucleophilic substitution reaction on a quinoline system: the synthesis of amino analogues of nitroxoline

A reliable protocol for the synthesis of a series of 8-amino analogues of pharmacologically interesting nitroxoline (5-nitro-8-hydroxyquinoline) is described. The unprecedented displacement of the cyanomethoxy group of an O-cyanomethylated quinoline derivative by various primary and secondary amines selectively affords 5-nitroquinolin-8-ylamines in moderate-to-high yields. The reactions were accelerated significantly under microwave conditions in comparison with conventional heating.     

Heterogeneous Wide Range <Emphasis Type="Italic">pH</Emphasis>-sensing Materials Allowing Ratiometric Fluorescence Detection Based on Structurally Rigid Analogs of 2,6-distyrylpyridine

The new sensing materials based on the microsized silica gel powder with non-covalently immobilized structurally rigid analogs of 2,6-distyrylpyrydine ((3E,5E)-3,5-dibenzylidene-8-phenyl-1,2,3,5,6,7-hexahydrodicyclopenta[b,e]pyridines) were developed and tested. Most of the investigated compositions demonstrate linear ratiometric fluorescence response on pH in the physiologically important interval (pH 6–9). The compound with the greatest number of protolytic centers within the studied series demonstrated the widest pH sensitivity range, however in this case the analytical signal was the lowest. The prospects for the practical application of the investigated materials in the fiber optics sensing devices were outlined.