Highly stereoselective radical carbonylations of gem-dihalocyclopropane derivatives with CO

A couple of radical carbonylations of gem-dihalocyclopropanes 1 using CO and Bu3SnH (formylation) or Bu3Sn(CH2CH=CH2) (allylacylation) successfully proceeded to give trans and cis adducts (2 and 3) with good to excellent stereoselectivity (trans/cis = >99/1-75/25 or 17/83-1/99). The formylation of 2,3-cis-disubstituted 1,1-dihalocyclopropanes enhanced trans selectivity (trans/cis = >99/1-95/5), whereas both 2,3-cis-disubstituted and 2-monosubstituted 1,1-dihalocyclopropanes underwent allylacylation with nearly complete trans selectivity (trans/cis = >99/1). Inherently less reactive gem-dichloro- and bromochlorocyclopropanes than gem-dibromocyclopropanes served as favorable substrates. [reaction: see text].     

Synthesis of hyperbranched carbohydrate polymers by ring-opening multibranching polymerization of anhydro sugar

The synthesis of novel hyperbranched carbohydrate polymers, prepared by the ring-opening multibranching polymerizations of anhydro and dianhydro sugars, is described. The hyperbranched carbohydrate polymers were formed by the cationic polymerization of 1,6-anhydro-beta-D-hexopyranose, 1,4-anhydrotetritol, 2,3-anhydrotetritol, and 1,2:5,6-dianhydro-D-mannitol. These polymerizations proceeded without gelation to produce water-soluble hyperbranched carbohydrate polymers with controlled molecular weights and narrow polydispersities. The values for the degree of branching of the polymers were in the range of 0.28-0.50. The polymerization method, which proceeds through a ring-opening reaction by a proton-transfer reaction mechanism, is a facile method leading to a spherical carbohydrate polymer with a high degree of branching.     

Exchange of Methyl‐ and Azobenzene‐Terminated Alkanethiols on Polycrystalline Gold Studied by Tip‐Enhanced Raman Mapping

Mixed thiol self‐assembled monolayers (SAMs) presenting methyl and azobenzene head groups were prepared by chemical substitution from the original single‐component n‐decanethiol or [4‐(phenylazo)phenoxy]hexane‐1‐thiol SAMs on polycrystalline gold substrates. Static contact‐angle measurements were carried out to confirm a change in the hydrophobicity of the functionalized surfaces following the exchange reaction. The mixed SAMs presented contact‐angle values between those of the more hydrophobic n‐decanethiol and the more hydrophilic [4‐(phenylazo)phenoxy]hexane‐1‐thiol single‐component SAMs. By means of tip‐enhanced Raman spectroscopy (TERS) mapping experiments, it was possible to highlight that molecular replacement takes place easily and first at grain boundaries: for two different mixed SAM compositions, TERS point‐by‐point maps with <50 nm step sizes showed different spectral signatures in correspondence to the grain boundaries. An example of the substitution extending beyond grain boundaries and affecting flat areas of the gold surface is also shown.     

Significance of water quality and radiation wavelength for UV photolysis of PhCs in simulated mixed solutions

Ultraviolet (UV) photolysis of sixteen pharmaceutical compounds (PhCs) in mixed solutions with four types of water and two sets of UV radiation was investigated. UVC (254 nm) photolysis was ineffective at eliminating a large number of PhCs while a big number of them were refractory. However, vacuum UV (VUV: 185 nm + 254 nm) photolysis in the same experimental conditions eliminated the PhCs almost completely. The eliminations in ultrapure water (UPW), tap water (TW) and Neya River water (NRW) and their organic/inorganic contents were inversely correlated, which was more evident in VUV photolysis. Natural organic matter (NOM) in NRW did not have an impact in indirect photolysis, but effluent organic matter (EfOM) in secondary-treated effluent (NWTPE) enhanced indirect photolysis, which was more evident in VUV photolysis underlining the point that radiation wavelength/intensity can be a limiting factor in organic-rich waters. Moreover, VUV photolysis was far superior (90% mineralization) to UVC photolysis (10% mineralization) for PhCs mineralization. The greatly enhanced elimination and mineralization efficiencies observed for VUV photolysis were attributed to accelerated direct photolysis with 185 nm wavelength and indirect photolysis involving ^·OH. The results demonstrated efficacy of VUV photolysis in wastewater treatment and its potential use as a tertiary treatment.      

Synthesis and properties of long‐chain branched poly(ether sulfone)s by self‐polycondensation of AB2 type macromonomers

Long‐chain branched poly(ether sulfone)s (PESs) were synthesized via self‐polycondensation of AB₂ macromonomers. The linear PES oligomers synthesized by self‐polycondensation of 4‐chloro‐4′‐(4‐hydroxyphenyloxy)diphenyl sulfone were terminated with 4‐(3,5‐methoxyphenoxy)‐4′‐fluorodiphenyl sulfone to form AB₂ macromonomer precursors. After conversion from methoxy to hydroxy groups, the AB₂ macromonomers were self‐polycondensed to form long‐chain branched PESs. NMR measurements support the formation of the target macromonomers ( = 2930–67,800 (g mol^?1); M_n = number average molecular weight) and long‐chain branched PESs. Gel permeation chromatography with multiangle light scattering measurements indicated the formation of high‐molecular‐weight (M_w) polymers over 10⁴. The root‐mean‐square radius of gyration (R_g) suggests that the shape of the long‐chain branched PES synthesized from small AB₂ macromonomers in solution is similar to that of hyperbranched polymers. Increasing resulted in larger R_g, suggesting a transition from hyperbranched to a linear‐like architecture in the resulting long‐chain branched PESs. Rheological measurements suggested the presence of strongly entangled chains in the long‐chain branched PES. Higher tensile modulus and smaller elongation at the break were observed in the tensile tests of the long‐chain branched PESs. It is assumed that the enhanced molecular entanglement points may act as physical crosslinks at room temperature. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1825–1831     

Glycoconjugated polymer: Synthesis and characterization of poly(vinyl saccharide)‐block‐polystyrene‐block‐poly(vinyl saccharide) as an amphiphilic ABA triblock copolymer

Styrene (St) was polymerized with α,α′‐bis(2′,2′,6′,6′‐tetramethyl‐1′‐piperidinyloxy)‐1,4‐diethylbenzene ( 1 ) as an initiator (bulk, [St]/] 1 ] = 570) at 120 °C for 5.0 h to obtain polystyrene having 2,2,6,6‐tetramethylpiperidiloxy moieties on both sides of the chain ends ( 2 ) with a number‐average molecular weight (M_n) of 14,300 and a polydispersity index [weight‐average molecular weight/number‐average molecular weight (M_w/M_n)] of 1.14. 4‐Vinylbenzyl glucoside peracetate ( 3a ) was polymerized with 2 as a macromolecular initiator and dicumyl peroxide (DCP) as an accelerator in chlorobenzene at 120 °C. The polymerization with the [ 3a ]/[ 2 ]/[DCP] ratio of 30/1/1.2 for 5 h afforded a product in a yield of 73%; it was followed by purification with preparative size exclusion chromatography to provide the ABA triblock copolymer containing the pendant acetyl glucose on both sides of the chain ends ( 4a ; M_n = 21,000, M_w/M_n = 1.16). Similarly, the polymerization of 4‐vinylbenzyl maltohexaoside peracetate produced the ABA triblock copolymer containing the pendant acetyl maltohexaose on both side of the chain end ( 4b ; M_n = 31,800, M_w/M_n = 1.11). Polymers 4a and 4b were modified by deacetylation into amphiphilic ABA triblock copolymers containing the pendant glucose and maltohexaose as hydrophilic segment, 5a and 5b , respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3978–3985, 2006     

Simultaneous measurement of several near-parallel surfaces with wavelength-shifting interferometry and a tunable phase-shifting method

Wavelength-shifting interferometry can distinguish in frequency space interference signals from different surfaces, and therefore allows the measurement of optical thickness variation between several quasi-parallel surfaces of a composite transparent object. Frequency analysis of the signal spectrum with a tunable phase-shifting formula can then detect the phase of the individual signals. We have devised a tunable phase-shifting method which uses a freely adjustable number of intensity samples and can be adapted to any frequency spectrum. To extract the signal reliably, two properties of the phase-shifting method are particularly important: it should suppress cross-talk from unwanted frequencies, and it should allow for some variation in the signal frequency. We show that a carefully designed sampling function envelope will combine these benefits, and demonstrate the technique in measurements of three different composite objects each consisting of three reflecting surfaces. The importance of phase-shift linearisation is discussed, and methods for selecting optimal set-up parameters are given.     

Role of bis(monoacylglycero)phosphate in propranolol binding to phospholipid membranes under acidic conditions as measured by high‐performance frontal analysis/capillary electrophoresis

Bis(monoacylglycero)phosphate (BMP) is localized in acidic organelles such as late endosomes or lysosomes. It has been reported that BMP levels increase under phospholipidosis induced by cationic amphiphilic drugs. In the present study, the effect of BMP on the binding of propranolol (PRO) to phospholipid liposomes under acidic conditions was investigated. Binding experiments were conducted by high‐performance frontal analysis/capillary electrophoresis. PRO showed nonspecific binding to BMP‐containing liposomes (BMP:phosphatidylcholine = 1:4), when numbers of bound drug molecules per lipid molecule (r) ranged 0.01–0.06. Total binding affinity increased depending on the BMP content. Binding affinity was decreased by low ionic strength, or by substitution of BMP with diacylglycerol, suggesting that electrostatic interactions were involved. The binding‐enhancement effect of BMP was almost equivalent to that of phosphatidylglycerol, and slightly larger than that of phosphatidylserine. An acidic environment (pH 5.0) decreased total binding affinity to BMP‐containing liposomes. This could be explained by the pH‐partition theory (i.e., the loss in affinity was caused by a decrease in the neutral form of the drug accessible to the membrane core). These results suggest that PRO binding is enhanced by BMP in late endosomes or lysosomes, whereas an acidic environment weakens such binding.     

Pendant structure governed anion sensing property for sulfonamide‐functionalized poly(phenylacetylene)s bearing various α‐amino acids

The colorimetric detection of anionic species has been studied for α‐amino acid‐conjugated poly(phenylacetylene)s, which were prepared by the polymerization of the ethyl esters of N‐(4‐ethynylphenylsulfonyl)‐L ‐alanine, L ‐isoleucine, L ‐valine, L ‐phenylalanine, L ‐aspartic acid, and L ‐glutamic acid using Rh⁺(2,5‐norbornadiene)[(η⁶‐C₆H₅)B^?(C₆H₅)₃] as the catalyst in CHCl₃. The one‐handed helical conformations of all the sulfonamide‐functionalized polymers were characterized by Cotton effects in the circular dichroism spectra. The addition of anions with a relatively high basicity, such as tetra‐n‐butylammonium acetate and fluoride, induced drastic changes in both the optical and chiroptical properties. On the other hand, anions with a relatively low basicity, such as tetra‐n‐butylammonium nitrate, azide, and bromide, had essentially no effects on the helical conformation of all the sulfonamide‐functionalized polymers. The anion signaling property of the sulfonamide‐functionalized polymers possessing α‐amino acid moieties was significantly affected by the installed residual amino acid structures. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1683–1689, 2010