Synthesis of selectively labeled D-fructose and D-fructose phosphate analogues locked in the cyclic furanose form

2,5-Anhydroglucitol and 2,5-anhydromannitol and their 6-phosphate and 1,6-diphosphate derivatives are cyclic analogues of the alpha and beta anomers of D-fructofuranose, D-fructofuranose-6-phosphate, and D-fructofuranose-1,6-diphosphate. They were synthesized from protected D-mannose or D-glucose. The synthetic method was developed with emphasis on selective (2)H labeling of these compounds, as a model for (3)H incorporation, which will be used for further biochemical studies. A key cyclization step, based on a benzyl ether nucleophilic attack on an activated alcohol, constructed the ring system. The stereochemistry at C(2) (alpha/beta anomers) and at C(5) (D sugar) was controlled by selective epimerizations. Mono- and diphosphate analogues were obtained from the same intermediate by changing the sequence of deprotection and phosphorylation steps.     

Selective site controlled nucleophilic attacks in 5-membered ring phosphate esters: unusual C-O vs. common P-O bond cleavage

Clean endocyclic C-O bond cleavage has been achieved in the reactions of 5-membered phosphate triesters with various nucleophiles.     

cis-3,5-Dibenzylidene-1,2,4-tritellurole,a novel organotellurium heterocycle

The reaction of sodium phenylethynyltellurolate with ethereal hydrogen chloride afforded, in addition to $\text{trans}$-2,4-dibenzylidene-1,3-di telluretane, a product shown to be the title compound by an X-ray crystallographic analysis.     

Spectroscopy of Ethylenedione and Ethynediolide: A Reinvestigation

In an effort to characterize the electronic states of ethylenedione, OCCO, photoelectron‐photofragment coincidence (PPC) spectroscopy was applied to measure anions at m/z 56 and 57 using a pulsed discharge of glyoxal vapor and N₂O. PPC measurements at a photon energy of 3.20 eV yield photoelectron spectra in coincidence with either neutral photofragments or stable neutral products. The measurements showed that primarily stable neutral products were formed, with photoelectron spectra consistent with the oxyallyl diradical, C₃H₄O, and acetone enolate radical, C₃H₅O. The spectra were also found to have features nearly identical to those reported for OCCO and HOCCO by Sanov and co‐workers. The stability of the neutral products, as well as an examination of spectra reported for the oxyallyl anion and acetone enolate show that the previous assignments of OCCO and HOCCO are in error, and are instead attributed here to the oxyallyl diradical, C₃H₄O, and the acetone enolate radical, C₃H₅O.     

Label-free LC-MS/MS quantitative proteomics for large-scale biomarker discovery in complex samples

Proteomic platforms that enable researchers to profile a high number of proteins across large sets of complex samples hold a great potential for biomarker discovery. LC-MS/MS-based methods can be used to analyse many samples without the need for protein labelling. As the analysis is a sequential process, the performance of the system has to be consistent throughout the entire experiment. In this study we used a set of spiked serum samples as well as a set of 55 clinical serum samples from schizophrenia patients and healthy volunteers to show that the label-free proteomic approach yields reproducible results across a large number of samples and can be used to accurately measure the relative protein abundance. Using this approach, we identified 1709 serum proteins covering a dynamic range of over three orders of magnitude. We believe that label-free quantitative proteomics is especially suited for biomarker discovery in large sample sets.     

Electroinitiated polymerization of vinylic monomers in polar systems. I. Contribution of the electrolysis of methanol to free-radical polymerization

Electrolytic polymerization of acrylates and methacrylates in methanol solution containing lithium acetate as electrolyte was investigated under currents ranging from 10 to 100 mA. Polymer yield increases up to a limiting current value, beyond which it decreases. This abnormal behavior is discussed. A free-radical mechanism is suggested.     

An unexpected rearrangement during mitsunobu epimerization reaction of sugar derivatives

Mitsunobu reaction on the glucose derivative (3S,4R,5R,6R)-3,4,5, 7-tetrabenzyloxy-6-hydroxy-1-heptene yielded an unexpected rearrangement major product. Its structure was determined as (3R,4R, 5R,6S)-4,5,6,7-tetrabenzyloxy-3-hydroxy-1-heptene. The suggested rearrangement mechanism involves an initial intramolecular cyclization, followed by ring opening by the nucleophile p-nitrobenzoate. Product distribution of the Mitsunobu reaction was substrate-dependent, with the corresponding mannose derivative (the 3R epimer) giving less of the initial intramolecular reaction products and the corresponding galactose derivative (the 5S epimer) yielding almost exclusively the expected epimerization product. Varying the Mitsunobu reaction conditions (addition of base and using nonpolar solvent) led to the expected epimerization product of the glucose derivative.     

Electroinitiated polymerization of vinylic monomers in polar systems. III. Polymerization of acrylates and methacrylates in alcohol solutions

Methyl, ethyl, and n-butyl acrylates and methacrylates are polymerized by electroinitiation in methanol–, ethanol–, and n-propanol–electrolyte mixtures in which the monomers are soluble whereas the polymers obtained are insoluble. The technique of changing the polarity of the electrodes described earlier was used. The relationships between molecular weights and polymer yields as function of current density, initial monomer concentration and dielectric constant of the solvent are described. A kinetic scheme for the initiation, propagation, and termination is given.