Thermodriven Micrometer‐Scale Aqueous‐Phase Separation of Amphiphilic Oligoethylene Glycol Analogues

Thermoresponsive materials with a lower critical solution temperature (LCST) are receiving growing attention, of which examples of non‐polymeric small molecules are limited. Monodisperse oligoethylene glycol amphiphiles that contain aromatic units with a LCST in water have been developed and applied to peptide extraction. Concentration‐dependent hysteretic transmittance changes were observed in response to temperature elevation and reduction. Dynamic light scattering measurements and phase contrast microscopy revealed the formation of micrometer‐sized aggregates upon heating at a concentration above 5.0 mM ; these aggregates self‐assembled to form larger aggregates upon cooling before dissolution. The “interaggregate” interactions are likely to cause the hysteretic behavior. As an application of this thermodriven phase separation, selective extraction of peptide fragments containing high percentages of hydrophobic and aromatic amino acid residues was successfully demonstrated.     

Degradation profiles in aged EPDM water seals using focused ion beam-scanning electron microscopy

The degradation of an ethylene–propylene-diene (EPDM) rubber seal used in a water supply system was investigated using focused ion beam-scanning electron microscopy (FIB-SEM). The EPDM rubber seal was used for 3 years within the temperature range 20–40 °C in a city water system. The accretions present on the surface of the EPDM seal after use were observed by SEM and were found to consist of iron and oxygen atoms based on energy dispersive X-ray spectroscopy (EDS) analysis. A cross-sectional depth image of the EPDM rubber was obtained by FIB-SEM, after slicing the EPDM rubber with a focused Gallium ion beam. Iron and oxygen atoms in the cross-section of the EPDM rubber were detected through EDS. The distribution of iron was comparable to that of oxygen derived from the carbonyl groups generated by the degradation of EPDM, suggesting that iron ions may promote the degradation of natural rubber through catalytic effects.     

Analysis of heterocyclic amines in hair by on-line in-tube solid-phase microextraction coupled with liquid chromatography−tandem mass spectrometry

Mutagenic and carcinogenic heterocyclic amines (HCAs) are formed during heating of various proteinaceous foods, but human exposure to HCAs has not yet been elucidated in detail. To assess long-term exposure to HCAs, we developed a simple and sensitive method for measuring HCAs in hair by automated on-line in-tube solid-phase microextraction (SPME) coupled with liquid chromatography–tandem mass spectrometry (LC–MS/MS). Using a Zorbax Eclipse XDB-C8 column, 16 HCAs were analyzed within 15 min. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40 μL sample at a flow rate of 200 μL min⁻¹ using a Supel-Q PLOT capillary column as an extraction device. The extracted HCAs were easily desorbed from the column by passage of the mobile phase, with no carryover observed. This in-tube SPME LC–MS/MS method showed good linearity for HCAs in the range of 10–2000 pg mL⁻¹, with correlation coefficients above 0.9989 (n = 18), using stable isotope-labeled HCA internal standards. The detection limits (S/N = 3) of 14 HCAs except for MeAαC and Glu-P-1 were 0.10–0.79 pg mL⁻¹. This method was successfully utilized to analyze 14 HCAs in hair samples without any interference peaks, with quantitative limits (S/N = 10) of about 0.17–1.32 pg mg⁻¹ hair. Using this method, we evaluated the exposure to HCAs in cigarette smoke and the suitability of using hair HCAs as exposure biomarkers.     

Synthesis of the Aziridinomitosene Skeleton by Application of Guanidinium Ylide‐Mediated Aziridination

An aziridinomitosene skeleton, a basic core of mitomycin antibiotics, was straightforwardly prepared from N‐(p‐toluenesulfonyl)indole‐2‐carboxaldehyde in 16% overall yield by successive reactions of guanidinium ylide‐mediated aziridination, InCl₃‐catalyzed epimerization of trans‐3‐(indol‐2‐yl)aziridine‐2‐carboxylate, leading to the cis‐derivative, and dehydrative cyclization.     

Synthesis of Polymers by Using Fluorene. VI. Free-Radical and Anionic Polymerizations of 9-Fluorenyl and 9-Phenyl-9-fluorenyl Methacrylates

9-Fluorenyl (FMA) and 9-phenyl-9-fluorenyl methacrylates (PFMA) were prepared from methacryloyl chloride with 9-fluorenol and from silver methacrylate with 9-phenyl-9-fluorenyl chloride, respectively. The polymerizations of FMA and PFMA were studied by using α,α′-azobisisobutyronitrile (AIBN), n-butyllithium (n-BuLi), and n-BuLi-(?)-sparteine (Sp) complex in toluene and tetrahydrofuran (THF). Only PFMA polymers obtained with the n-BuLi-Sp complex showed a specific rotation ([α]_D ²¹ ?3 to ?16° in THF).

The number-average molecular weights of the FMA and PFMA polymers were 7 700-16 900 and 1 400-4 700, respectively.     

Synthesis of 2′,3′-Dideoxy-2′-Fluorokanamycin A

2′,3′-Dideoxy-2′-fluorokanamycin A (23) was prepared by condensation of 6-azido-4-0-benzoyl-2,3,6-trideoxy-2-fluoro-α-D-ribo-hexopyranosyl bromide (13) and a protected disaccharide (19). Methyl 4,6-0-benzylidene-3-deoxy-β-D-arabino-hexopyranoside (5) prepared from methyl 4,6-0-benzylidene-3-chloro-3-deoxy-β-D-allo-hexopyranoside (1) by oxidation with pyridinium chlorochromate followed by reduction with Na₂ S₂O₄ was fluorinated with the DAST reagent to give methyl 4,6-O-benzylidene-2,3-dideoxy-2-fluoro-β-D-ribo-hexopyranoside (7). Successive treatment of 7 with NBS, NaN₃ and SOBr₂ gave 13. The structure of the final product (23) was determined by the ¹H and ¹⁹F and shift-correlated 2D NMR spectra.     

Preparation,characterization, and polymerization of maleimidobenzoxazine monomers as a novel class of thermosetting resins

New series of benzoxazine‐based monomers, namely maleimidobenzoxazines, were prepared with hydroxyphenylmaleimide, formalin, and various amines (e.g., aniline, allylamine, and aminophenyl propargyl ether). The structure of the novel monomers was confirmed by IR, ¹H NMR, and elemental analysis. The monomers were easily dissolved in many common organic solvents. Differential scanning calorimetry of the novel monomers showed exotherms at different temperature ranges that corresponded to the polymerization regime of benzoxazine and maleimide along with other functionalities such as allyl or propargyl, if any. IR was studied to follow the progress of the curing reaction of maleimidobenzoxazine after various thermal treatments. The thermal cure of the monomers at 250 °C afforded a novel network structure that combined polybenzoxazine and polymaleimide. The dynamic mechanical analyses showed that the storage moduli of the thermosets derived from maleimidobenzoxazine were kept constant up to high temperatures. The glass‐transition temperatures were as high as 241–335 °C. Moreover, thermogravimetric analyses revealed that the thermosets did not show any weight loss up to about 350 °C, with char yields ranging from 62 to 70% at 800 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1424–1435, 2006