Stereoselective synthesis of the insect growth regulator (S)-(+)-hydroprene through Suzuki–Miyaura cross-coupling

A stereoselective synthesis of the insect growth regulator (S)-(+)-hydroprene has been developed in seven steps with 50% overall yield starting from an easily available bromoester. Through using the Suzuki–Miyaura cross-coupling as the key C_sp2–C_sp2 bond forming step, high level of stereocontrol of the C2–C3 olefin is achieved.     

Total synthesis of bleomycin A21)

Bleomycin A2 has been synthesized for the first time.     

Crystal orientation in a semicrystalline polymer in relation to deformation of polymer spherulites. III. Small-angle light scattering

Small-angle polarized light scattering from a deformed three-dimensional spherulite is formulated on the basis of the deformation model proposed in Part II of this series. The intensity distribution of scattered light is discussed chiefly for the cross-polarization condition, the so-called H_v polarization, as a function of elongation of the spherulite. In the undeformed state, the scattered intensity distribution forms the typical fourleaf clover pattern, and the intensity decreases with increasing fraction of crystals oriented randomly (type R crystals) within the crystal lamellae of the spherulites. In a system composed of type R crystals and folded-chain crystals (type B crystals) within the lamellae, the four-leaf pattern moves to the horizontal zone near the equator with increasing elongation of the spherulite, and, simultaneously, extends to some extent to the vertical zone near the meridional direction as a parameter measuring the ease of lamellar untwisting increases. In a system composed, in addition to type R and type B crystals, of crystals transformed from type B to type C_a and type C_r due to tilting and unfolding of polymer chains, respectively, within the crystal lamellae an eight-leaf pattern appears, even at small elongation up to about 30%. Each lobe of the eight-leaf pattern undergoes a characteristic change with increasing elongation. In both systems, the scattered intensity increases with sharpening of orientation distribution of crystals within the crystal lamellae.     

Photoelectron spectra and orbital assignments by sum rule consideration: Ethyl and n-propyl fluorides

The He I photoelectron (PE) spectra of C₂H₅F and n-C₃H₇F have been obtained. The PE spectra indicate that the first ionization potentials are about 0.4 eV higher than those of the parent alkanes owing to the inductive effect of fluorine. All the PE bands obtained here have been interpreted in terms of appropriate p-type localized MO's using the sum rule described previously by the authors. Orbital energy diagrams involving the inductive effect of fluorine are illustrated. The semi-empirical CNDO/2 and MINDO/2 methods were also employed to help confirm the present orbital assignments.     

Optimization of a method for determining dioxin in whole blood samples based on solvent extraction and simplified cleanup

Dioxins, including polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/Fs) and coplanar polychlorinated biphenyls (Co-PCBs), such as mono-ortho-PCBs and non-ortho-PCBs, are environmental pollutants that have deleterious effects on human health. Although screening of blood samples for dioxins is necessary, the current methods are time-, reagent- and labor-intensive. To optimize the extraction and cleanup of dioxins, we have designed a column chromatography method, coupled with a water washing step. We used a tandem simplified multilayer silica gel-activated carbon dispersed silica gel column (TS-ML-AC) rather than the conventional two columns. We compared three liquid-liquid extraction (LLE) methods and two pressurized liquid extraction (PLE) methods, when used with this column. For each of these extraction methods, we compared the quantity of lipid obtained when the water washing step was omitted and when it was performed by shaking 30 times by hand or 30 min by a machine. We found that TS-ML-AC was superior to the conventional pair of columns in that only about one third of the solvent and only one quarter of the time was necessary. Of the five extraction methods, the acetone/hexane PLE (AcP) method was superior, since it reduced the amount of organic solvent to half or less of the amount required for the LLE methods. The cleanup step using water was best accomplished by the hand-shaking method. Our results indicate that, for the analysis of dioxin in whole blood samples, the use of AcP together with TS-ML-AC and water washing by hand shaking should be used.     

Effective pretreatment of human serum samples for dioxin analysis by solid phase extraction and blue-chitin column cleanup

For the analysis of dioxins, polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/Fs) and coplanar polychlorinated biphenyls (Co-PCBs), devising simple and economical methods is important, especially for mass screening of human exposure. Pretreatment of samples, namely the extraction and cleanup methods that are widely used at present, needs to be improved for savings in time, manpower, and solvent consumption. In the present study, we applied solid phase extraction (SPE) using octadecyl (C18) and a blue-chitin column in place of liquid-liquid extraction (LE) and an active-carbon column with serum samples, frequently used for assessment of human exposure. Efficacy of the new pretreatment methods was demonstrated by successful high resolution gas chromatography-high resolution mass spectrometry (HRGC-HRMS) of the major 17 PCDDs/Fs and 12 Co-PCBs that are on the list of WHO/IPCS (1997) hazardous dioxins with toxic equivalent factor (TEF) values. SPE is timesaving and requires less manpower and organic solvent as compared with the LE that is presently widely used. Concerning cleanup with blue-chitin, the amount of toluene applied as eluent could be reduced to 1/3, as compared with the active-carbon case. The combination of SPE and blue-chitin for pretreatment of serum saves time and manpower, is accurate and uses less organic solvent than LE with active carbon cleanup.     

A note on portfolio optimization with path-dependent utility

This paper considers the portfolio selection with preferences depending on the history of the wealth process. The maximization problem of the expected terminal utility consisting of the combination of two kinds of preferences is discussed in a continuous trading setting. Especially we focus on the relationship between the portfolio risk and the goal seeking behavior of the financial agent. The numerical example shows how the risk sensitivity affects the optimal portfolio and the corresponding expected path-dependent utility. Finally, we provide a criterion to choose buy and hold or buy and sell strategies.     

Synthesis, stabilities, and redox behavior of Di(1-azulenyl)(6-azulenyl)methylium hexafluorophosphates. Generation of a donor-acceptor-substituted neutral radical by azulenes

Several di(1-azulenyl)(6-azulenyl)methanes and 1,3-bis[(1-azulenyl)(6-azulenyl)methyl]azulenes were prepared by the condensation reaction of azulenes with diethyl 6-formylazulene-1,3-dicarboxylate under acidic conditions. The products were converted into di(1-azulenyl)(6-azulenyl)methylium hexafluorophosphates and azulene-1,3-diylbis[(1-azulenyl)(6-azulenyl)methylium] bis(hexafluorophosphate)s via hydride abstraction reaction with DDQ following the exchange of counterions. These mono- and dications exhibited high stability with large pK(R)(+) values (5.6-10.1), despite the captodative substitution of azulenes. The electrochemical reduction of the monocations upon cyclic voltammetry (CV) exhibited a reversible two-step, one-electron reduction wave with a small difference between the first reduction potential (E(1)(red)) and the second one (E(2)(red)), which exhibited the generation of highly amphoteric neutral radicals in solution. The electrochemical reduction of dications showed voltammograms, which were characterized by subsequent two single-electron waves and a two-electron transfer upon CV attributable to the formation of a radical cation, a diradical (or twitter ionic structure), and a dianionic species, respectively. Formation of a persistent neutral radical from a monocation was revealed by ESR and UV-vis spectroscopies and theoretical calculations. The ESR spectra of the neutral radical gave two hyperfine coupling constants: a(H) = 0.083 (6H) and 0.166 mT (9H) (g = 2.0024), indicating that an unpaired electron delocalizes over all three of the azulene rings. The stable monoanion, which shows the localization of the charge on the 6-azulenyl substituent, was also successfully generated from the di(1-azulenyl)(6-azulenyl)methane derivative.     

The reaction of perfluoro-2,4-dialkyloxolanes with anhydrous aluminum chloride

Several kinds of perfluoro-2,4-dialkyloxolanes (A), having such alkyl groups as R_fR′_fCF₃ (2a); R_fC₂F₅, R′_fCF₃ (3a); R_fCF₃, R′_fC₂F₅ (4a); R_fR′_fC₂F₅ (5a); R_fCF₃, R′_fnC₃F₇ (6a) on the 2 and 4 positions of the oxolane ring, respectively, were treated with AlCl₃ in a heterogeneous reaction to give the corresponding perfluoro-2,5,5-trichloro-2,4-dialkyloxolanes (B). For purposes of comparison, the respective reactions of perfluoro-2-methyl-oxolane (la), perfluoro-2-n-butyloxolane (7a), and perfluoro-2, 5-dimethyloxolane (8a) with AlCl₃ were also conducted. An increasingly higher reaction temperature was needed for the reaction of A with AlCl₃ to give B as the carbon number of A increased. Cis- and trans-perfluoro-4-chloro-2,4-dimethyl-γ-butyrolactones (2c) were obtained from the hydrolytic reactions of cis- and trans-perfluoro-2,5,5-trichloro-2,4-dimethyloxolanes (2b), respectively, with fuming H₂SO₄. Physical properties and ¹⁹F nmr data are given for these new compounds.