Replacement of a carbonyl group of cyclic ketones by an oxygen atom: A four-step transformation of cyclic ketones into cyclic ethers

We describe a new and versatile method for transforming cyclic ketones into cyclic ethers with the same ring size in which the chirality adjacent to the carbonyl group of the ketones is retained.     

Moments of a statistic caused by random combinations or random matings

Summary Given two sets of sizek, {α ₁...,α _k} and {β ₁...,β _k} there arek! possible combinations of these two , and suppose there is apriori given a number corresponding to the partnership (α ₁,β _j}. The average of the numbers corresponding to is a random variable, and this paper presents the first five moments of the average, and an application in the study of an isolated human population is demonstrated.     

Controlled release of vitamin E from thermo-responsive polymeric physico-gel

Thermo-sensitive copolymer consists of poly(2-ethoxyethyl vinyl ether) and poly(hydroxyethyl vinyl ether) (EOVE200-HOVE400), whose sol-gel transition temperature was 20.5 degrees C, was synthesized and its applicability to a drug delivery system was examined. Vitamin E (VE) was enclosed in EOVE200-HOVE400 and the release of VE was measured by varying the temperature 10<-->30 degrees C. There was no release of VE from EOVE200-HOVE400 at 30 degrees C, while VE was released when the temperature was reduced to 10 degrees C.     

Contribution of oligosaccharides to protection of the H,K-ATPase beta-subunit against trypsinolysis

The proton-pumping H+,K+-adenosinetriphosphatase (H,K-ATPase), responsible for acid secretion by the gastric parietal cell, faces a harshly acidic environment, with some pepsin from neighboring chief cells, at its luminal surface. Its large catalytic alpha-subunit is mostly oriented cytoplasmically. The smaller beta-subunit (HKbeta), is mainly extracellular, with one transmembrane domain and a small cytoplasmic domain. Seven N-linked oligosaccharides in the extracellular domain of HKbeta are thought to contribute to protection of the H,K-ATPase, since previous work has shown that their complete removal, by peptide N-glycosidase F (PNGase F), greatly increased susceptibility of HKbeta to proteolysis. The possibility of graded protection by different numbers of oligosaccharides was investigated here with the use of mutant HKbeta cDNA, having various N-glycosylation sites mutated (Asn to Gln), transfected into HEK-293 cells. Membrane preparations, two days after transfection, were solubilized in 1% Triton X-100 and subjected to trypsinolysis (pH 8, 37 degrees C, trypsin:protein 1:10-1:25). Relative amounts of HKbeta remaining after 20 min trypsin were determined, after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and probing of Western blots with an antibody to the HKbeta extracellular domain, by chemiluminescent development of blots and densitometry of resulting films. Maturely glycosylated HKbeta was made significantly more susceptible to trypsin than wild type when at least five oligosaccharides were deleted, while the high-mannose form (pre-beta), from the endoplasmic reticulum, became significantly more susceptible than wild-type pre-beta with removal of only two or more oligosaccharides. For each mutant, and wild type, pre-beta was consistently more susceptible than the mature form. While the number, and kind, of oligosaccharides seem to affect protection for HKbeta against trypsinolysis, other aspects of protein maturation, including proper folding of peptide domains and possible subtle alterations of conformation during Golgi processing, are also likely to contribute to this protection.     

Design and synthesis of dual inhibitors of acetylcholinesterase and serotonin transporter targeting potential agents for Alzheimer's disease

Highly efficient acetylcholinesterase (AChE) and serotonin transporter (SERT) dual inhibitors, (S)-4 and (R)-13 were designed and synthesized on the basis of the hypothetical model of AChE active site. Both compounds showed potent inhibitory activities against AChE and SERT. [structure: see text]     

Computational analysis of side-chain conformations in polyaspartates exhibiting reversible helical sense inversion in the solid state

Poly(β-phenylpropyl -aspartate), poly(β-phenylbutyl -aspartate), and poly(β-phenylpentyl -aspartate) exhibit a reversible transformation from a right-handed -helix (_R) to a left-handed ω-helix (ω_L) in the solid state. During this transition, the infrared (IR) dichroism of the side-chain ester group and the birefringence change drastically, showing that the side-chain conformations are different for these two helices. In the present study, for the purpose of elucidating the preferred side-chain conformation in each helix, we performed the computational analyses. The energy contours, the directions of the IR transition moments and the anisotropies in polarizability as functions of the first two dihedral angles of the side chain, χ₁ and χ₂ were calculated. Then, comparing them with the experimental IR dichroism and birefringence data, we elucidated the specific side-chain conformation preferred for each _R or ω_L skeleton. The preferred values of (χ₁, χ₂) were found to be (−75, −60°) for _R and (180, 45°) for ω_L.     

Precursor mediated cycloaddition reaction of ethylene to the Si(100)c(4 x 2) surface

We report the direct observation of a precursor state for the cycloaddition reaction (the di-sigma bond formation) of ethylene on Si(100)c(4 x 2) using high-resolution electron energy loss spectroscopy at low temperature, and the meta-stable precursor state is identified as a weakly bonded pi-complex type. The activation energy from the pi-complex precursor to the di-sigma bonded species is experimentally estimated to be 0.2 eV. First-principles calculations support the pi-complex precursor mediated cycloaddition reaction of ethylene on Si(100)c(4 x 2).     

Phase-vanishing reactions that use fluorous media as a phase screen. Facile,controlled bromination of alkenes by dibromine and dealkylation of aromatic ethers by boron tribromide

In fluorous triphasic reactions, such as bromination of alkenes by dibromine and dealkylation of aromatic ethers by boron tribromide, the middle fluorous phase acts as a liquid membrane permitting passive transport of the reagents at the bottom to the top layer involving the substrates, thereby regulating the reactions.     

The stereochemical investigation of 8-membered 1,3,6-dioxazocines via NMR

The stereochemical properties of 2-, 4-, 7-, and 8-methyl substituted 5,6,7,8-tetrahydro-1,3,6-dioxazocines have been investigated by their pmr and cmr spectroscopy. On the basis of the coupling constant and γ-effects, the stereochemical structures are discussed.     

The effects of a remote stereogenic center in the Lewis base catalyzed aldol additions of chiral trichlorosilyl enolates

Chiral trichlorosilyl enolates bearing a remote stereogenic center were employed in the phosphoramide-catalyzed aldol reaction. The additions of the methyl ketone enolates proceeded with only moderate diastereoselectivities. The addition of the Z-enolate to various aldehydes selectively produced the syn relative diastereomers. In both cases, the effect of the beta-silyloxy stereogenic center was modest, and the internal diastereoselection was mainly controlled by the catalyst. [reaction: see text]