Reaction of N,N-dimethylselenocarbamoyl chloride with nucleophiles. Preparation of diselenocarbamates, selenothiocarbamates, and selenoureas

Reactions of N,N-dimethylselenocarbamoyl chloride prepared by using LiAlHSeH with nucleophiles such as lithium alkylselenolate, lithium alkylthiolate, and amines afford the corresponding diselenocarbamates, selenothiocarbamates, and selenoureas. The crystal structure of the Se-phenyl N,N-dimethyldiselenocarbamate was also determined by X-ray diffraction.     

Precision synthesis of regioregular poly(3‐hexylthiophene) with low dispersity using a zincate complex catalyzed by nickel with the ligand of 1,2‐bis(dicyclohexylphosphino)ethane

Regioregular poly(3‐hexylthiophene) (P3HT) has been a commonly used p‐type semiconducting material for solution processable organic electronics. To establish a living system of “Negishi‐type catalyst‐transfer polycondensation (NCTP)” using zincate complex as a synthetic method for well‐defined P3HT having predictable molecular weight (MW) and low dispersity (?), the ligands of Ni catalyst were optimized. As a result, a ligand of 1,2‐bis(dicyclohexylphosphino)ethane produced P3HTs with highly controlled number average MWs (1650–32,800) and very low ? values (1.03–1.17). The polymerization results were strongly influenced by steric hindrance based on the factors of cone angle and bite angle of Ni catalysts, and/or electron‐donating ability of phosphine ligands. In addition, we succeeded in the two‐stage polymerization of P3HT and the synthesis of P3HT‐b‐poly(3‐octadecylthiophene), the latter of which is the first demonstration by NCTP using zincate complex. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2287–2296     

Distribution of late gadolinium enhancement in end-stage hypertrophic cardiomyopathy and dilated cardiomyopathy: Differential diagnosis and prediction of cardiac outcome

Background

The prognostic implications of late gadolinium enhancement (LGE) have been evaluated in ischemic and non-ischemic cardiomyopathies. The present study analyzed LGE distribution in patients with end-stage hypertrophic cardiomyopathy (ES-HCM) and with dilated cardiomyopathy (DCM), and tried to identify high risk patients in DCM.

Methods

Eleven patients with ES-HCM and 72 with DCM underwent cine- and LGE-cardiac magnetic resonance and ultrasound cardiography. The patient outcome was analyzed retrospectively for 5 years of follow-up.

Results

LGE distributed mainly in the inter-ventricular septum, but spread more diffusely into other left ventricular segments in patients with ES-HCM and in a certain part of patients with DCM. Thus, patients with DCM can be divided into three groups according to LGE distribution; no LGE (n = 24), localized LGE (localized at septum, n = 36), and extensive LGE (spread into other segments, n = 12). Reverse remodeling occurred after treatment in patients with no LGE and with localized LGE, but did not in patients with extensive LGE and with ES-HCM. The event-free survival rate for composite outcome (cardiac death, hospitalization for decompensated heart failure or ventricular arrhythmias) was lowest in patients with extensive LGE (92%, 74% and 42% in no LGE, localized LGE, and extensive LGE, p = 0.02 vs. no LGE), and was comparable to that in patients with ES-HCM (42%).

Conclusions

In DCM, patients with extensive LGE showed no functional recovery and the lowest event-free survival rate that were comparable to patients with ES-HCM. The analysis of LGE distribution may be valuable to predict reverse remodeling and to identify high-risk patients.     

Synthetic Studies on Sialoglycoconjugates 66: First Total Synthesis of a Cholinergic Neuron-Specific Ganglioside GQ1bα1

Abstract

A first total synthesis of a cholinergic neuron-specific ganglioside, GQ1bα (IV³Neu5Acα, III⁶Neu5Acα, II³Neu5Acα₂-Gg₄Cer) is described. Regio- and stereo-selective monosialylation of the hydroxyl group at C-6 of the GalNAc residue in 2-(trimethylsilyl)ethyl O-(2-acetamido-2-deoxy-3,4-O-isopropylidene-β-d-galactopyranosyl)-(1→4)-O-(2,6-di-O-benzyl-β-dgalactopyranosyl)-(1→4)- O-2,3,6-tri-O-benzyl-β-dglucopyranoside (4) with methyl (phenyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-2-thio-d glycero-d galacto-2-nonulopyranosid) onate (5), and subsequent dimericsialylation of the hydroxyl group at C-3 of the Gal residue with methyl [phenyl 5-acetamido-8-O-(5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-d glycero-α-d galacto-2-nonulopyranosylono-1′,9-lactone)-4, 7-di-O-acetyl-3,5-dideoxy-2-thio-d glycero-d galacto-2-nonulopyranosid]onate (7), using N-iodosuccinimide (NIS)-trifluoromethanesulfonic acid (TfOH) as a promoter, gave the desired hexasaccharide 8 containing α-glycosidically-linked mono- and dimeric sialic acids. This was transformed into the acceptor 9 by removal of the isopropylidene group. Condensation of methyl O-(methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-d glycero-α-d galacto-2-nonulopyranosylonate)-(2→3)-2,4,6-tri-O-benzoyl-1-thio-β-dgalactopyranoside (10) with 9, using dimethyl(methylthio)sulfonium triflate (DMTST) as a promoter, gave the desired octasaccharide derivative 11 in high yield. Compound 11 was converted into α-trichloroacetimidate 14, via reductive removal of the benzyl groups, O-acetylation, removal of the 2-(trimethylsilyl)ethyl group, and treatment with trichloroacetonitrile, which, on coupling with (2S,3R,4E)-2-azido-3-O-benzoyl-4-octadecene-1,3-diol (15), gave the β-glycoside 16. Finally, 16 was transformed, via selective reduction of the azido group, coupling with octadecanoic acid, O-deacylation, and hydrolysis of the methyl ester group, into the title ganglioside 18 in good yield.     

Synthetic Studies on Sialoglycoconjugates 81: Synthesis of Positional Isomers of Sialyl Lewis X Epitope Containing 1-Deoxy-d Glucose in Place of N-Acetylglucosamine,and Their Inhibitory Activity to Selectin-Mediated Adhesion

Abstract

Three sialyl-Le^x epitope analogs, which carry fucose and α-sialyl-(2→3)-galactose residues at O-2 and O-3, O-3 and O-2, and O-4 and O-6 positions of 1-deoxy-D-glucose backbone, respectively, have been synthesized. Glycosylation of 1,5-anhydro-4,6-O-benzylidene-D-glucitol (1) or 1,5-anhydro-6-O-benzoyl-2,3-di-O-benzyl-d-glucitol (4) prepared from 1,5-anhydro-d-glucitol, with methyl 2,3,4-tri-O-benzyl-1-thio-β-L-fucopyranoside (5) using dimethyl(methylthio)sulfonium triflate (DMTST) as a promoter, afforded the corresponding fucosyl 1,5-anhydro-d-glucitol derivatives 7, 8 and 9. Glycosylation of 7, 8 or 10 derived from 9, with methyl O-(methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-d-glyceroα-d-galacto-2-nonulopyranosylonate)-(2→3)-2,4,6-tri-O-benzoyl-1-thio-β-d-galactopyranoside (11) in the presence of DMTST gave the expected tetrasaccharide derivatives 12, 16 and 20. Hydrolysis of the benzylidene group in 12 and 16 gave compounds 13 and 17. Finally 13, 17 and 20 were transformed, by reductive removal of the benzyl groups, O-deacylation and subsequent hydrolysis of the methyl ester, into the sialyl-Le^x epitope analogs 15, 19 and 22, respectively.     

Synthetic Studies on Sialoglycoconjugates 49: Novel Disaccharides and Lactams Composed of Sialic Acid and 1-Deoxynojirimycin-Potential for Biomedical Application

Abstract

Sialic acid-containing glycoconjugates participate in a variety of biological functions on cell surfaces, not only serving as receptors for hormones, viruses and bacteria but also as mediators in cell growth, differentiation, adhesion, oncogenesis and so on. For example, influenza virus^1,2 and tripanosoma cruzi ^3,4 recognize sialic acid in the time of infection to animal cells. Recently, the sialyl-Le^x (sLe^x) and sialyl-Le^a (sLe^a) carbohydrate epitopes have been highlighted as the ligands for selectins, a family of cell adhesion molecules involved in leukocyte traffic^5,6 and tumor metastasis.⁷ 1-Deoxynojirimycin (DNJ) and related compounds are well known⁸ as the potent inhibitors of a-glycosidases and glycoprotein-processing enzymes. Some of the Nsubstituted DNJ derivatives have been noted as antidiabetic and anti-HIV agents.     

Fluorescence study of thermotropic liquid-crystalline polyesters

Photoluminescence behavior (polarization, lifetime) related to liquid-crystal (LC) formation was examined for the thermotropic liquid-crystalline polyesters poly [(ethylene terephthalate)-co-(p-oxybenzoate)] (PET40/OBA60) (OBA content: 60 mol %) and poly [(ethylene 2,6-naphthalene dicarboxylate)-co-(p-oxybenzoate)] (PEN50/OBA50) (OBA:50 mol %). The Growth of liquid-crystalline (LC) phases of PET40/OBA60 proceeded during annealing. even at low temperature (e.g., 138°C) and were promoted by an increase in annealing temperatures T_a in the experimental temperature range 138–260°C. The concentration dependence of fluorescence spectra of PET40/OBA60 in solution suggested that the fluorescences at 325 and 395 nm can be attributed to monomer and ground-state dimer, respectively. The increase in dimer fluorescence intensity and the decrease in the fluorescence anisotropy ratio r from 0.06 to –0.14 were observed with growth of LC phases. These effects are explained by an increase in the ground-state dimer population and a slight change in the dimer configuration, respectively. PEN50/OBA50 showed monomer fluorescence at 395 nm due to naphthalenedicarboxylate segments and excimer fluorescence at 430 nm. The r value for the excimer fluorescence decreased from zero to about ?0.14 with growth of the LC phase. Such an extraordinary phenomena, in comparison with the usual excimer fluorescences which occurs through energy migration, could be interpreted as the result of formation of high-concentration excimer sites induced by chain orientation in LC domains. © 1993 John Wiley & Sons, Inc.     

Preparation of polysiloxanes from silicic acid. IX. Partially silylated silicic acid and its spinnability

The reaction in different molar ratios of trimethylchlorosilane to silicic acid offered partially silylated silicic acids PSSX (X = OH) with various degrees of silylation. Esterification and acetylation of PSSX (X = OH) with 1-butanol or acetylchloride gave polysiloxanes PSSX (X = OBuⁿ and OCOCH₃). Some of them showed an excellent spinnability and provided a fine fiber with a length of about 250 cm. A fiber drawing test from concentrated PSSX solutions of various solvents revealed that spinnability markedly depended on the DS, functional group X of PSSX, and solvent. Spinnability may also be correlated to solubility parameter of PSSX and solvent.     

Membrane reactor performance of steam reforming of methane using hydrogen-permselective catalytic SiO2 membranes

Hydrogen production by steam reforming of methane using catalytic membrane reactors was investigated first by simulation, then by experimentation. The membrane reactor simulation, using an isothermal and plug-flow model with selective permeation from reactant stream to permeate stream, was conducted to evaluate the effect of permselectivity on membrane reactor performance – such as methane conversion and hydrogen yield – at pressures as high as 1000 kPa. The simulation study, with a target for methane conversion of 0.8, showed that hydrogen yield and production rate have approximately the same dependency on operating conditions, such as reaction pressure, if the permeance ratio of hydrogen over nitrogen ((H₂/N₂)) is larger than 100 and of H₂ over H₂O is larger than 15. Catalytic membrane reactors, consisting of a microporous Ni-doped SiO₂ top layer and a catalytic support, were prepared and applied experimentally for steam reforming of methane at 500 °C. A bimodal catalytic support, which allows large diffusivity and high dispersion of the metal catalyst, was prepared for the enhancement of membrane catalytic activity. Catalytic membranes having H₂ permeances in the range of 2–5 × 10⁻⁶ m³ m⁻² s⁻¹ kPa⁻¹, with H₂/N₂ of 25–500 and H₂/H₂O of 6–15, were examined for steam reforming of methane. Increased performance for the production of hydrogen was experimentally obtained with an increase in reaction-side pressure (as high as 500 kPa), which agreed with the theoretical simulation with no fitting parameters.