Stereoselective synthesis of 2-methylenepyrrolizidines by tandem cyclization of N-propargylaminyl radicals

Tandem cyclization of N-propargylaminyl radicals, generated by N-chlorination of (E)-alk-4-enylamines 2a-d and 2f followed by treatment with tributyltin radical, afforded 2-methylenepyrrolizidines 3a-d and 3f in a highly stereoselective manner. A similar radical cyclization of (Z)-N-propargyl-1-methyl-5-phenylpent-4-enylamine (2e) gave pyrrolizidine 3b having the same stereochemistry as that obtained from the E isomer 2b.     

Drug–tea polyphenol interaction

Propericiazine (PCZ) is an antipsychotic agent used for the treatment and the prevention of relapse of schizophrenia. We found that when an oral solution containing PCZ was mixed with a green tea drink, the residual content of PCZ was reduced by forming an insoluble complex between PCZ and tea polyphenol. In this study, the mechanism underlying the incompatibility of PCZ with green tea polyphenol (GTP) in the solution was clarified by isothermal titration microcalorimetry (ITC). Both solutions of 27.4 mM PCZ and 2.2 mM (?)-epigallocatechin gallate (EGCg), which is a main ingredient of GTP, were mixed and then PCZ in the filtrate was reduced to approximately 60 %. According to measurement at 298 K by ITC, PCZ formed an insoluble complex with EGCg at an associate constant (K) of 4.75 × 10² M^?1 exothermically, ΔH = ?40.0 kJ mol^?1. When (?)-epicatechin gallate (ECg) was used as the GTP, PCZ interacted with ECg with K and ΔH values of 3.74 × 10² M^?1 and ?22.1 kJ mol^?1, respectively. On the other hand, little heat of the reaction between PCZ and (?)-epigallocatechin or (?)-epicatechin was observed. The results indicated that the main reason for this incompatibility was the formation of an insoluble complex by PCZ and a gallate-type GTP such as EGCg and ECg in the aqueous solution.     

Excess enthalpies of binary mixtures of butylamines + propanols at 298.15 K

The molar excess enthalpies of eight systems of butylamines + propanols were determined at 298.15 K using a twin-microcalorimeter. All excess enthalpies were exothermic and large. An equilibrium constant K ₁ expressed in terms of mole fractions and standard thermodynamic properties of formation (Δ_f H, Δ_f G, Δ_f S) of 1:1 complex were evaluated by ideal mixtures of monomeric molecules and their associated complexes. Concentration dependence of the FT-Raman spectrum showed systematic changes of bands. Spectroscopic considerations based on this and ab initio calculations on molecules were performed at the Mp2/6-311G(d,p) level of theory. Interaction energies between butylamine and propanol were calculated by the supermolecular and NBO methods. The results were discussed with previous results to clarify the steric and positional effect of the amino and hydroxyl group.     

Methyl torsional potentials of rotational isomers of m-methylanisole studied by spectral hole-burning spectroscopy

Laser-induced fluorescence (LIF) excitation spectra of m-methylanisole in a supersonic jet were measured. Two series of progressions were observed in the spectrum, originating at 36048 and 36115 cm⁻¹, which were successfully assigned to the transitions to the methyl internal rotational vibronic levels of the two isomers, i.e. cis and trans isomers, with the aid of hole-burning spectrum measurements and quantum-chemical calculations. The progression for the trans isomer was observed up to the 6a₁ band, while only the 3a₁ band in addition to the 0a₁ and 1e bands was observed for the cis isomer. This finding can be explained by the conformational change upon the electronic excitation; the 60° rotation of the methyl torsional angle takes place for the trans isomer but not for the cis isomer.     

Studies on the constituents of Gardenia species. III. New iridoid glycosides from the leaves of Gardenia jasminoides cv. fortuneana Hara

Two new iridoid glycosides, 7 beta,8 beta-epoxy-8 alpha-dihydrogeniposide (1) and 8-epiapodantheroside (2), were isolated, together with six known (3-8) and three artifact (9-11) iridoids, from the leaves of Gardenia jasminoides cv. fortuneana Hara. Their structures were established based on chemical and spectral data.     

Finding Degradation Trigger Sites of Structural Materials for Airplanes Using X‐Ray Microscopy

Macroscopic properties of carbon fiber‐reinforced plastic (CFRP) and environmental barrier coating (EBC), widely used for airplanes, can be deteriorated by local cracks or degradation (“trigger sites”). We have tried to find these trigger sites using x‐ray microscopy (XM), which can provide the 2D or 3D images of the chemical states and microstructures. Crack initiation in CFRP was observed in a non‐destructive manner in multi‐scales (nm‐mm). 3D chemical‐state mapping of Yb in EBC was achieved with high resolution (<50 nm). In addition to XM, in‐situ observations at high temperatures were conducted for obtaining complementary information. X‐ray absorption spectroscopy (XAS) and x‐ray diffraction (XRD) analysis were performed simultaneously up to 1773 K. Dynamic XAS with short time‐resolution (<10 ns) was conducted to investigate changes in the local structure of metal. These approaches can help us identify degradation trigger sites in the materials.     

Effects of Pluronics surfactants on morphology and porosity of hematite particles produced from forced hydrolysis reaction

The shape and porosity of hematite particles, produced from a forced hydrolysis reaction of acidic FeCl₃ solution, were controlled by using Pluronics as nonionic surfactants (0–4 wt.%). Pluronics possess a nominal formula of (PEO) _x –(PPO) _y –(PEO) _x . The effect of Pluronics with low hydrophilicity (PEO contents were less than 50 mol%) was small and provided spherical particles the same as that of the system without Pluronics (control system). However, Pluronics with higher hydrophilicity (PEO contents were over 50 mol%) gave ellipsoidal hematite particles. This effect on the particle morphology was enhanced by an increase in their molecular weight. On the other hand, the Pluronics possessing an opposite nominal formula [(PPO) _x –(PEO) _y –(PPO) _x ] exhibited no effect on the particle shape; it only depressed phase transformation from ?-FeOOH to hematite. Not only the morphology but also the pore size of hematite particles was controlled from nonporous to mesoporous by using Pluronics. The N₂ adsorption experiment and t-plot curve analysis revealed that the hematite particles changed from mesoporous to microporous by an increase in the concentration of Pluronics. On the other hand, in the presence of very low amounts of Pluronics molecules (0.1 wt.%), nonporous hematite particles were produced via strong aggregation of PN particles by their hydrogen bonding between hydroxyl and PEO or PPO groups. The dynamic light scattering measurement for the system with Pluronics clarified the existence of polynuclear (PN) particles with a hydrodynamic particle diameter (D _a) of ca. 40 nm after these were aged for 6 h. The size of PN particles remained constant at ca. 40 nm during aging time of 12 h～3 days, but the scattering intensity was decreased. This decrease in the scattering intensity reveals that the number of PN particles is reduced by aggregation. The transmission electron microscope, inductively coupled plasma atomic emission spectroscopy, and total organic carbon analysis measurements employed on the systems produced for ellipsoidal particles elucidated that the formation of ellipsoidal hematite particles is attributed to the adsorption of Pluronics on the surfaces of PN and growing hematite particles.     

A practical synthesis of L-ribose

L-Ribose was synthesized by a simple four-step method with overall yield of 76.3% from a protected L-arabinose derivative, which is a compatible intermediate for the synthesis of L-deoxyribose. The key step of this strategy is the Swern oxidation and subsequent stereoselective reduction accompanied by inversion of the 2-hydroxy group of protected L-arabinose.     

A heme degradation enzyme, HutZ, from Vibrio cholerae

HutZ, one of the crucial proteins of the iron uptake system in Vibrio cholerae, was purified, which binds to heme at a stoichiometry of 1 : 1. In the presence of ascorbic acid, the HutZ-bound heme degrades via the same intermediates observed in heme oxygenase, suggesting that HutZ works as a heme degradation enzyme.