Regiospecific synthesis of 2‐substituted furanonaphthoquinones

The naturally‐occurring furanonaphthoquinones 1a‐d have been synthesized from 3‐furancarboxylic acid and 2,3‐dimethoxybenzaldehyde via the Birch reduction‐elimination.     

Interactions and influence of α-cyclodextrin on the aggregation and interfacial properties of mixtures of nonionic and zwitterionic surfactants

The interactions of α-cyclodextrin (α-CD) with the nonionic surfactant decanoyl-N-methyl-glucamide (Mega-10) and the zwitterionic surfactant dimethyldodecylammoniopropanesulfonate (DPS) in their mixed system have been studied using interfacial tension, fluorescence, and nuclear magnetic resonance measurements. From the plots of interfacial tension vs. log of total surfactant concentration, we have obtained values of the surface excess of surfactant, the critical micellar concentration (cmc), the standard free energy of micelle formation, and association constant of surfactant/α-CD inclusion complexes (assuming a 1:1 stoichiometry). A comparison of the K _a values obtained for the interaction between α-CD and DPS and Mega-10, respectively, shows that DPS interacts stronger with α-CD than Mega-10. The experimental mixed cmc was analyzed by the pseudophase separation model and regular solution theory for the evaluation of ideality or nonideality of the mixed micelle formation. The interaction parameters in the mixed micelle and the micelle composition at different mole fractions of DPS were also computed. The fluorescence anisotropy (r) values of rhodamine B decreases with the increase of α-CD concentrations.     

Measurement of the rate of nu(e) + d --> p + p + e(-) interactions produced by (8)B solar neutrinos at the Sudbury Neutrino Observatory

Solar neutrinos from (8)B decay have been detected at the Sudbury Neutrino Observatory via the charged current (CC) reaction on deuterium and the elastic scattering (ES) of electrons. The flux of nu(e)'s is measured by the CC reaction rate to be straight phi(CC)(nu(e)) = 1.75 +/- 0.07(stat)(+0.12)(-0.11)(syst) +/- 0.05(theor) x 10(6) cm(-2) s(-1). Comparison of straight phi(CC)(nu(e)) to the Super-Kamiokande Collaboration's precision value of the flux inferred from the ES reaction yields a 3.3 sigma difference, assuming the systematic uncertainties are normally distributed, providing evidence of an active non- nu(e) component in the solar flux. The total flux of active 8B neutrinos is determined to be 5.44+/-0.99 x 10(6) cm(-2) s(-1).     

Constraints on nucleon decay via invisible modes from the Sudbury Neutrino Observatory

Data from the Sudbury Neutrino Observatory have been used to constrain the lifetime for nucleon decay to "invisible" modes, such as n-->3nu. The analysis was based on a search for gamma rays from the deexcitation of the residual nucleus that would result from the disappearance of either a proton or neutron from 16O. A limit of tau(inv)>2 x 10(29) yr is obtained at 90% confidence for either neutron- or proton-decay modes. This is about an order of magnitude more stringent than previous constraints on invisible proton-decay modes and 400 times more stringent than similar neutron modes.     

One-Step Synthesis of the 1-Azaspiro[5.5]undecane Skeleton Characteristic of Histrionicotoxin Alkaloids from Linear Substrates via Hg(OTf)2-Catalyzed Cycloisomerization

Histrionicotoxin (HTX) alkaloids isolated from the poison arrow frogs possess a unique structure characterized by a 1-azaspiro[5.5]undecane skeleton common to the HTX family. The unique molecular architecture of HTXs and the interest as potential target drugs have prompted synthetic chemists to promote the total synthesis so far. However, all of the synthetic strategies to access the 1-azaspiro[5.5]undecane framework of HTXs take a multistep approach from linear starting materials due to stepwise construction of either six-membered carbo- or azacycle. Herein, we report the direct one-step construction of the 1-azaspiro[5.5]undecane skeleton from linear amino ynone substrates bearing an N-methoxycarbonyl group utilizing our mercuric triflate (Hg(OTf)₂)-catalyzed cycloisomerization reaction. The utility of this novel methodology was demonstrated by the total and formal syntheses of HTX-235A and HTX-283A, respectively, from the azaspirocycle.     

Interactions Between the Cationic Surfactants Bearing Different Polar Head Groups: Interfacial,Conductivity, NMR,and Fluorescence Studies

Interfacial tension (γ), conductivity (κ), nuclear magnetic resonance (NMR), and fluorescence measurements have been carried out to study the mixed interfacial and micellar behavior of cationic surfactants cetyltributylphosphonium bromide (CTBB) and the cetyltrimethylammonium bromide (CTAB). From the γ versus log C _s plots, the values of critical micellar concentration (cmc) and various interfacial parameters were computed. From κ measurements, the equivalent conductivities of the monomers (Λ _mon), the micelles (Λ _mic) states and the degree of counterion dissociation (δ) have been evaluated. The cmc values have been analyzed in the context of the pseudophase separation model and regular solution theory. The interaction parameters, β^m and β^σ, in the mixed micelle as well as in the mixed monolayer, respectively, also have been computed. The self‐diffusion coefficients for the micelles have been evaluated by using NMR spectroscopy. From the fluorescence quenching method, the mean micellar aggregation number (N _agg) of the pure and mixed micelles has been obtained from the slope of the ratio of fluorescence intensities in the absence and in the presence of quencher (ln (I _1,0/I ₁) versus [Q] plots. It was found that the incorporation of CTBB into the mixed micelle decreases the N _agg. The microviscosity of the fluorescence probe Rhodamine (RB) was monitored by using fluorescence polarization measurements. The values of fluorescence anisotropies (r) indicate that the penetration of CTBB monomer into CTAB micelles produced less rigid mixed micelles.     

Synthesis of (±)-penlanfuran

The title compound was efficiently synthesized from 3-furoic acid and 3-bromoanisole via the Birch reduction.     

Direct,rapid titration of 8-quinolinol : Application of constant-current potentiometry

The major problems in the direct bromination titration of the important analytical reagent 8-quinolinol have been slow reaction rate and difficulty of end-point detection. A reaction-rate study showed that perchloric acid as the titratiun medium gives a sufficiently high reaction rate for direct titration. End-points are simply and conveniently detected using constant-current potentiometry. Metal ions do not interfere. Excellent agreement between titration by the proposed method and the conventional indirect iodomrtric method was observed.