Efficient phenolic oxidations using μ-oxo-bridged phenyliodine trifluoroacetate

The excellent oxidizing behavior of the μ-oxo-bridged phenyliodine trifluoroacetate 1 is revealed during the phenolic oxidations mediated by hypervalent iodine(III) reagents. The use of the μ-oxo-bridged compound 1 instead of PhI(OAc)₂ (PIDA) and PhI(OCOCF₃)₂ (PIFA) during the oxidative cyclization of phenols involving carbon-oxygen, carbon-nitrogen, and carbon-carbon bond formations could produce spirocyclized cyclohexadienones in comparable or somewhat better yields. Thus, we have concluded that the unique reagent 1 is a promising alternative to PIDA and PIFA, and the use of reagent 1 as a reasonable choice is recommended for the hypervalent iodine(III)-mediated phenolic oxidations as well as other transformations.     

Photochemistry of a putative new class of sensory rhodopsin (SRIII) coded by xop2 of Haloarcular marismortui

Baliga et al. (2004) [1] reported the existence of a functionally unpredictable opsin gene, named xop2, in Haloarcula marismortui, a holophilic archaeon. Ihara et al. [38] performed molecular phylogenetic analysis and determined that the product of xop2 belonged to a new class of opsins in the sensory rhodopsins. This microbial rhodopsin was therefore named H. marismortui sensory rhodopsin III (HmSRIII). Here, we functionally expressed HmSRIII in Escherichia coli cell membranes to examine the photochemistry. The wavelength of maximum absorption (λ(max)) for HmSRIII was 506nm. We observed a very slow photocycle that completed in ～50s. Intermediates were defined as M (λ(max)～380nm), N (λ(max)～460nm) and O (λ(max)～530nm) 0.01s after the flash excitation. The nomenclature for these intermediates was based on their locations along the absorption maxima of bacteriorhodopsin. Analysis of laser-flash-photolysis data in the presence and absence of azide gave the following results: (1) an equilibrium between N and O was attained, (2) the direct product of the M-decay was O but not N, and (3) the last photo-intermediate (HmSRIII') had a λ(max) similar to that of the original, and its decay rate was very slow. Resonance Raman spectroscopy revealed that this N-intermediate had 13-cis retinal conformation. Proton uptake occurred during the course of M-decay, whereas proton release occurred during the course of O-decay (or exactly N-O equilibrium). Very weak proton-pumping activity was observed whose direction is the same as that of bacteriorhodopsin, a typical light-driven proton pump.     

Synthesis of a novel one-handed helical poly(phenylacetylene) bearing poly(l-lactide) side chains

The living ring-opening polymerization of l-lactide was carried out by using organocatalyst to synthesize the molecular weight controlled poly(l-lactide) with an phenylacetylenyl end group (HCCPLLA), then the homopolymerization of HCCPLLA was performed by using two different rhodium catalysts. Low molecular weight poly-PLLA₆-1 (M_w,SEC-MALLS = 46,700) was synthesized by using Rh(nbd)BPh₄ as the catalyst, and higher molecular weight poly-PLLA₆-2 (M_w,SEC-MALLS = 471,000) was synthesized by using the [Rh(nbd)Cl]₂/Et₃N catalyst system. Then high molecular weight poly-PLLA₂₀, poly-PLLA₂₉, and poly-PLLA₆₈ were successfully synthesized by using the [Rh(nbd)Cl]₂/Et₃N catalyst system. The α values of the poly-PLLAs using [Rh(nbd)Cl]₂/Et₃N catalyst system were all in the range of 0.6–0.8, this means that these polymers possess linear flexible chain. It is concluded that [Rh(nbd)Cl]₂/Et₃N was more suitable for the synthesis of the cylindrical polymer brush, poly-PLLA with high molecular weight. The analyses of the CD spectra indicated that poly-PLLA possesses a predominantly one-handed helical conformation, temperature and solvents had significant influences on the helical structure of poly-PLLA.     

Synthesis of maresin 1 and (7S)-isomer

Maresin 1 (with the 7R carbon) and (7S)-maresin 1 were synthesized stereoselectively. The conjugated triene system was constructed by Pd-catalyzed coupling of the trans cis-dienylborane (the C10–C22 part) with the trans vinyl iodide corresponding to the C1–C9 part. The stereogenic centers at C7 and C14 were created by Ru-catalyzed asymmetric reduction of ketone and asymmetric epoxidation/kinetic resolution of the racemic alcohol, respectively.     

Enzymatic screening of microalgae as a potential source of natural antioxidants

Extracts of over 100 species of microalgae both from nature and from laboratory cultures were screened for antioxidant activity. As an assay for antioxidant function, we examined the inhibition of the activity of two oxidizing enzymes, lipoxygenase and tyrosinase. Water, ethanol, and methanol extracts of microalgae were used for the assay. It was found that lipoxygenase and tyrosinase activities were inhibited by the extract of several microalgae. Our results suggest that these species of microalgae have useful antioxidant activity, and they will be further examined for potential biotechnological exploitation. The aim of our screening was to identify potential sources of natural antioxidant compounds, which if found to be sufficiently potent and nontoxic, might eventually replace the chemicals that are currently used as food additives and cosmetics, in order to prevent food spoilage and their oxidation.     

Star‐shaped polystyrenes with glycoconjugated periphery and interior: Synthesis and entrapment of hydrophilic molecule

Star‐shaped polystyrenes with acetyl glucose in the periphery and interior were synthesized via two‐steps, 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO)‐mediated living radical polymerizations. In the first step, styrene (St) was polymerized with 4‐[1′‐(2″,2″,6″,6″‐tetramethyl‐1″‐piperidinyloxy)ethyl]phenyl 2,3,4,6‐tetra‐O‐acetyl‐β‐D ‐glucopyranoside, 1 , at 120 °C to afford a TEMPO‐terminated polystyrene with acetyl glucose in the chain‐end, arm‐polymer 2 . Similarly, St was polymerized with 1‐phenyl‐1‐(2′,2′,6′,6′‐tetramethyl‐1′‐piperidinyloxy)ethane, 3 , to obtain a TEMPO‐terminated polystyrene, arm‐polymer 4 . In the second step, the coupling reaction of arm‐polymer 2 was performed using divinylbenzene (DVB) as a linking agent in m‐xylene at 138 °C, giving a star‐shaped polystyrene with acetyl glucose in the periphery, 5 . The coupling reaction of arm‐polymer 4 with DVB was carried out in the presence of 1 , which produced a star‐shaped polystyrene with acetyl glucose in the interior, 6 . Dynamic laser light scattering (DLS) measurements indicated that 5 and 6 existed as the particles in toluene with the average diameters ranging from 12–40 nm. The numbers of the arm (N_arm) were 12–23 and 6–64 for 5 and 6 , respectively, which were determined by their isolated yields and static laser light scattering (SLS) measurements. The numbers of the acetyl glucose units (N₁) were 12–23 and 9–104 for 5 and 6 , respectively, which were determined from specific rotation ([α]₃₆₅). Finally, 5 and 6 were modified by deacetylation using sodium methoxide, producing star‐shaped polystyrenes with glucose in the periphery and interior, 7 and 8 , respectively. The final architectures were found to entrap a hydrophilic molecule at their glycoconjugated periphery or interior in good solvents for polystyrene such as chloroform. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4373–4381, 2005     

Application of a surface plasmon resonance sensor to analyses of amine compounds with the use of a polymer film and an acid-base reaction.

A surface plasmon resonance (SPR) sensor was applied to analyses of some amine compounds (n-butylamine, isobutylamine, aniline, and N,N-dimethylaniline) by using a polymer film and an acid-base reaction in it. Poly(acrylamide) (PAA) was adopted as the polymer film and was immobilized on an Au film to prepare a sensor chip. Pivalic acid was entered into the PAA film as an acid. The PAA film with a thickness of 50 nm gave the highest sensitivity to the SPR sensor. Although water was better concerning the sensitivity for the SPR sensor as the solvent, ethanol was adopted because it dissolves well all of the amine compounds used. The Au film coated with the PAA film gave higher sensitivity for analyses of n-butylamine and isobutylamine, and lower sensitivity for analyses of aniline and N,N-dimethylaniline than an Au film without the PAA film. The PAA film containing pivalic acid gave 4-5 orders of magnitude higher sensitivity to the SPR sensor for analyses of all the amine compounds due to the reaction between pivalic acid and these amine compounds.     

Synthesis of well‐defined AB20‐type star polymers with cyclodextrin‐core by combination of NMP and ATRP

The synthesis of an AB₂₀‐type heteroarm star polymer consisting of a polystyrene arm and 20‐arms of poly(methyl methacrylate) or poly(tert‐butyl acrylate) was carried out using the combination of nitroxide‐mediated polymerization (NMP) and atom transfer radical polymerization (ATRP). The NMP of styrene was carried out using mono‐6‐[4‐(1′‐(2″,2″,6″,6″‐tetramethyl‐1″‐piperidinyloxy)‐ethyl)benzamido]‐β‐cyclodextrin peracetate ( 1 ) to afford end‐functionalized polystyrene with an acetylated β‐cyclodextrin (β‐CyD) unit (prepolymer 2 ) with a number‐average molecular weight (M_n) of 11700 and a polydispersity (M_w/M_n) of 1.17. After deacetylation of prepolymer 2 , the resulting polymer was reacted with 2‐bromoisobutyric anhydride to give end‐functionalized polystyrene with 20(2‐bromoisobutyrol)s β‐CyD, macroinitiator 4 . The copper (I)‐mediated ATRP of methyl methacrylate (MMA) and tert‐butyl acrylate (tBA) was carried out using macroinitiator 4 . The resulting polymers were isolated by SEC fractionation to produce AB₂₀‐type star polymers with a β‐CyD‐core, 5 . The well‐defined structure of 5 with weight‐average molecular weight (M_w)s of 13,500–65,300 and M_w/M_n's of 1.26–1.28 was demonstrated by SEC and light scattering measurements. The arm polymers were separated from 5 by destruction with 28 wt % sodium methoxide in order to analyze the details of their characteristic structure. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4271–4279, 2005     

Synthesis of water-soluble porphyrin and the corresponding highly planar benzoporphyrin without meso-substituents

Water-soluble bicycloporphyrin and benzoporphyrin having octacarboxyl groups are synthesized from the corresponding octaester porphyrin by simple hydrolyzing and heating procedures. These compounds are characterized by UV-vis, NMR and mass spectroscopies. The benzoporphyrin octacarboxylic acid exhibits extremely high planarity in spite of its poly-substitution.     

Determination of particle size by using incidence-angle dependence of spectral intensity for particle-size-measurement method by applying infrared attenuated-total-reflection technique and its simulations by using algebraic-simultaneous equations

A method using an incidence-angle dependence of the spectral intensity was proposed to determine a particle size in a particle-size measurement by applying an infrared attenuated-total-reflection (ATR) technique. A formula, which is proportional to the infrared ATR-spectral intensity, was constructed as a function of the particle size, amount of particles, and incidence angle, psi. Its psi dependences were calculated for SiO(2) particles of less than a mono layer on a Ge prism, and differed at every particle size. Some simulations of determining both particle size and particle amount were carried out for the samples of particles with sizes of 1 to 3 kinds by using algebraic-simultaneous equations with the software of Mathematica 5.2, and resulted in showing its usefulness.