Three-dimensional structures of OSW-1 and its congener

The 3D structures of an antitumor glycosylsterol OSW-1 and its closely related congener were investigated by NMR studies and an X-ray crystallographic analysis. The disaccharide moiety was found as a structural scaffold for the formation of a hydrophobic cluster by the biologically required functionalities.     

A Novel Non-Phosgene Process for Polycarbonate Production from CO2: Green and Sustainable Chemistry in Practice

This paper focuses on the world’s first non-phosgene process using CO₂ as starting material succeeded in development and industrialization by Asahi Kasei Corp. The Asahi Kasei Process enables high-yield production of high-quality PC having excellent properties and high-purity monoethylene glycol (MEG), starting from ethylene oxide (EO), by-produced CO₂ and bisphenol-A without waste and waste water. The innovative reactive distillation technologies in the monomer production and the innovative gravity-utilized, non-agitation polymerization reactor in the melt polymerization, led the new process to success. The monomer process consists of 3 production steps, ethylene carbonate (EC) from CO₂ and EO, dimethyl carbonate (DMC) and MEG from EC and MeOH, and diphenyl carbonate (DPC) and MeOH from DMC and PhOH. All intermediates are recycled. The new type polymerization reactor perfectly overcomes the difficulty based on the extremely high viscosity in the melt polymerization of DPC with Bis-A. The by-produced PhOH is recycled to the monomer process. The reduction of CO₂ emissions (0.173t/PC 1t) is also achieved, because CO₂ used as raw material is utilized as the main chain components of the products. Four commercial plants (Taiwan: 150,000 t/y, Korea: 2 plants of 65,000 t/y, Russia: 65,000 t/y) using the Asahi Kasei Process are now successfully operating, and the plant of 260,000 t/y in Saudi Arabia will start in 2010.     

Rapid and Slow Generation of 1‐Trifluoromethylvinyllithium: Syntheses and Applications of CF3‐Containing Allylic Alcohols,Allylic Amines,and Vinyl Ketones

1‐(Trifluoromethyl)vinylation is accomplished in two protocols by the in situ generation of thermally unstable 3,3,3‐trifluoroprop‐1‐en‐2‐yllithium ( 1 ): 1) a rapid lithium–halogen‐exchange reaction of 2‐bromo‐3,3,3‐trifluoroprop‐1‐ene ( 2 ) takes effect with sec‐BuLi at ?105 °C to generate vinyllithium 1 , which reacts with more reactive electrophiles, such as aldehydes and N‐tosylimines before its decomposition, to afford 2‐(trifluoromethyl)allyl alcohols and N‐[2‐(trifluoromethyl)allyl] sulfoamides in good yield; 2) treatment of 2 with nBuLi at ?100 °C causes a slow lithium–halogen exchange of 2 , which gives rise to a mixture of 1 and nBuLi. Vinyllithium 1 is preferentially trapped with less reactive electrophiles, such as N,N‐dimethylamides in the presence of BF₃?OEt₂, to afford 1‐(trifluoromethyl)vinyl ketones in good yield. Versatility of the products toward syntheses of CF₃‐containing ring‐fused cyclopentenones is also demonstrated by the Pauson–Khand reaction and the Nazarov cyclization.     

Chemical synthesis, folding, and structural insights into O-fucosylated epidermal growth factor-like repeat 12 of mouse Notch-1 receptor

Notch receptors are cell surface glycoproteins that play key roles in a number of developmental cascades in metazoa. The extracellular domains of Notch-1 receptors are composed of 36 tandem epidermal growth factor (EGF)-like repeats, many of which are modified at highly conserved consensus sites by an unusual form of O-glycan, with O-fucose. The O-fucose residues on certain EGF repeats may be elongated. In mammalian cells this can be a tetrasaccharide, Siaα2,3Galβ1,4GlcNAcβ1,3Fucα1→. This elongation process is initiated by the action of O-fucose-specific β1,3 N-acetylglucosaminyltransferases of the Fringe family. There is evidence that the addition of GlcNAc by Fringe serves as an essential modulator of the interaction of Notch with its ligands and the triggering of activation. Here we describe the efficient synthesis, folding, and structural characterization of EGF repeat 12 (EGF 12) of a mouse Notch-1 receptor bearing different O-fucose glycan chains. We demonstrate that the three disulfide bonds, Cys(456)-Cys(467) (C1-C3), Cys(461)-Cys(476) (C2-C4), and Cys(478)-Cys(487) (C5-C6) were correctly formed in the nonglycosylated as well as the O-fucosylated forms of EGF 12. Three-dimensional structural studies by NMR reveal that the methyl group of fucose is in close contact with ILe(475), Met(477), Pro(478) residues and this stabilizes the conformation of the antiparallel β-sheet of EGF 12. The addition of the GlcNAc residue on O-fucosylated EGF 12 induces a significant conformational change in the adjacent tripeptide sequence, Gln(462)Asn(463)Asp(464), which is a motif involved in the natural, enzymatic O-fucosylation at the conserved site (Cys(461)X(4)Ser/ThrCys(467)).     

Crystallization-controlled dynamic self-assembly and an on/off switch for equilibration using boronic ester formation

Macrocyclic boronic esters of different sizes can be prepared selectively from the same starting diboronic acid and 1,2-diol by means of an interesting dynamic self-assembly phenomena. More specifically, two kinds of macrocyclic boronic esters could be formed diastereoselectively and nearly quantitatively under neutral conditions by the addition of an appropriate guest molecule that acts as a template. Although a mixture of tetrol 1 and di(boronic acid) 2 in methanol gave only insoluble polymeric boronic esters, a soluble macrocyclic boronic ester, homo-[2+2], was obtained selectively in the presence of toluene as a guest molecule. Furthermore, when benzene was employed as a guest molecule, the selective formation of another macrocyclic boronic ester, hetero-[3+3], occurred. Interestingly, each of these macrocycles could be converted into the other in the presence of methanol and the appropriate guest molecule; however, under aprotic conditions, guest molecules encaged by the macrocyclic boronic ester could be exchanged without affecting its structure. Thus the presence or absence of a protic solvent could be used as a regulator to switch on or off the dynamic equilibrium of the system. In addition, investigation of the effect of reaction time, direct observation of the reaction mixture by NMR spectroscopy, and carrying out the reaction using optically active tetrol suggested that precipitation plays an essentially important role in the selective formation of the macrocyclic boronic esters. Thus, although both of [2+2] and [3+3] were present as solutes in the reaction mixture, the type of added guest molecule induced the selective precipitation of only one form of macrocyclic boronic ester, hence displacing the equilibrium of the system.     

Study on surface adsorption from cationic surfactant–electrolyte mixed aqueous solution including BF 4 − ion

The surface tension of aqueous mixtures of dodecyltrimethylammonium tetrafluoroborate (DTABF₄) and sodium tetrafluoroborate (NaBF₄) was measured as a function of total molality and composition of DTABF₄ at 298.15 K. The results were analyzed by originally developed thermodynamic equations and compared with those of dodecyltrimethylammonium bromide (DTAB)–sodium bromide (NaBr) mixed system. It was indicated that BF₄⁻ ions reduce the repulsion between DTA⁺ ions more effectively than Br⁻ ions in the adsorbed film. To investigate this difference more closely, the surface tension of DTAB–NaBF₄ and DTABF₄–NaBr mixed system was also measured. The data analysis revealed that BF₄⁻ ions are adsorbed positively even for the pure NaBF₄ system and preferentially to Br⁻ ions in these mixtures. Furthermore, it was concluded that the side-by-side arrangement suggested in the adsorbed film of 1-hexyl-3-methylimidazolium tetrafluoroborate (HMIMBF₄) is due to not only the positive adsorption of BF₄⁻ ions but also the capability of hydrogen bond formation between imidazolium ion and BF₄⁻ ions.     

Development of the new IC decapsulation technology

An IC is generally decapsulated with wet etching technology. The influences of environment and worker's health in usage and waste of the chemicals are seen as problems. Improvement of processing time is also needed. In order to overcome them, the laser processing technology is applied to IC decapsulation. In this paper, the relationship between processing condition and the processed surface quality is reported to select a suitable laser source. In addition, the new IC decapsulation technology, which is the combination of laser and wet etching, is proposed. To achieve the complex machining, firstly, the method of measuring the reflection light intensity of the laser is proposed to estimate the residual molding thickness. Secondly, the relationship between intensity of reflected laser and mold thickness to IC is shown to construct a mold thickness monitoring system. Finally, processing time and the volume of chemical solution used a process are compared with a conventional wet etching process.