Stereoselective reduction,methylation, and phenylation of the 13-carbonyl group in chlorophyll derivatives

Regioselective reduction of the 13-carbonyl group on the five-membered exo-ring of methyl pyropheophorbide-a, one of the chlorophyll-a derivatives, with sodium borohydride gave an epimeric mixture of (13¹R/S)-hydroxy-chlorins. The stereoselectivity was controlled by the steric effect of the (17S)-methoxycarbonylethyl group to afford the (13¹S)-rich secondary alcohol (25% de). The use of sterically large lithium tri(sec-butyl)borohydride as the reductant enhanced the stereoselectivity to 55% de. The regio- and stereoselective methylation and phenylation of the 13-CO of pyropheophorbide-a were observed using methyl and phenyl lithium, respectively. The major diastereomer of the tertiary alcohols obtained had the same configuration at the 13¹-stereogenic center as in the reduced product. All of the anion species (H^?, CH₃^?, and C₆H₅^?) favorably attacked the 13¹-carbon atom from the reverse side of the 17-propionate residue, that is, the less sterically crowded face of the 13-CO plane.     

Non‐hybridization single nucleotide polymorphism detection and genotyping assay through direct discrimination of single base mutation by capillary electrophoretic separation of single‐stranded DNA

The significant demands for single nucleotide polymorphism detection and genotyping assays have grown. Most common assays are based on the recognition of the target sequence by the hybridization with its specific probe having the complementary sequence of the target. Herein, a simple, label‐free, and economical non‐hybridization assay was developed for single nucleotide polymorphism detection and genotyping, based on the direct discrimination of single base mutation by simple capillary electrophoresis separation for single‐stranded DNA in an acidic electrophoretic buffer solution containing urea. Capillary electrophoresis separation of single‐base sequential isomers of DNA was achieved due to charge differences resulting from the different protonation properties of the DNA bases. Single nucleotide polymorphism detection and genotyping were achieved by discriminating the electropherogram pattern change, that is, peak number in the electropherogram, obtained by the proposed method. The successful practical application of the proposed method was demonstrated through single nucleotide polymorphism detection and genotyping on a known gene region of 84‐mer, in which guanine to adenine single‐base mutation is commonly observed, using a human hair sample in combination with genomic DNA extraction, polymerase chain reaction amplification, DNA purification from polymerase chain reaction products, and capillary electrophoresis separation.     

Spin Ice-like Magnetic Relaxation of a Two-dimensional Network based on Manganese(III) Salen-type Single-Molecule Magnets

Spin ice is an exotic type of magnetism displayed by bulk rare-earth pyrochlore oxides. We discovered a spin ice-like magnetic relaxation of [{Mn(saltmen)}₄{Mn(CN)₆}](ClO₄)⋅13 H₂O (saltmen²⁻=N,N′-(1,1,2,2-tetramethylethylene)bis(salicylideneiminate)). This magnetic system can be considered as a two-dimensional network of Mn^III salen-type single-molecule magnets (SMMs) in which each SMM unit (S_T=4) has two orthogonally oriented axial anisotropies and is connected ferromagnetically through the [Mn(CN)₆]³⁻ unit (S=1). This work illustrates that a two-dimensional SMM network with competition between the ferromagnetic interaction and local noncollinear magnetic anisotropies on SMMs is a new type of magnetic system exhibiting slow relaxation of magnetization with a Davidson-Cole-type broad distribution of the relaxation time.     

Concentrations of 137Cs and 40K in wild mushrooms collected in a forest on Noto Peninsula,Japan

A variety of wild mushrooms were collected in a forest on the Noto Peninsula, Japan, to determine the concentration of ¹³⁷Cs and ⁴⁰K. The wild mushroom species belong to the orders Agaricales and Aphyllophorales. The concentration of ¹³⁷Cs varied widely (1.4–4,100 Bq/kg dry weight) in mushrooms growing in soil. On the contrary, ¹³⁷Cs concentration levels were relatively low (1.9–20 Bq/kg-dry weight) in mushrooms growing on wood. The concentration of ⁴⁰K varied widely (12–2,400 Bq/kg-dry weight) in contrast with several previous reports that suggest relatively constant ⁴⁰K levels in mushrooms. Unusually low concentrations of ⁴⁰K were observed in a few mushroom species that had very hard fruiting bodies with peculiar shapes. The mean and median of ¹³⁷Cs concentration in the present study were similar to those previously reported for Japanese mushrooms. Among the Agaricales mushrooms, Entolomataceae and Tricholomataceae families growing in soil had the highest concentration of ¹³⁷Cs. Among the Aphyllophorales mushrooms, Gomphaceae and Ramariaceae families growing in soil also had the highest ¹³⁷Cs concentrations. The concentrations of ¹³⁷Cs and stable Cs in mushroom samples were positively correlated. The concentration ratio of ¹³⁷Cs/Cs differed between Agaricales and Aphyllophorales mushrooms. The average ¹³⁷Cs/Cs ratio in mushrooms growing in soil was similar to that calculated for the top soil (<5 cm deep) alone because the mycelia of the mushrooms were mainly distributed near the surface of the soil.     

Laser-photophoretic migration and fractionation of human blood cells

Laser photophoretic migration behavior of human blood cells in saline solution was investigated under the irradiation of Nd:YAG laser beam (532 nm) in the absence and the presence of the flow in a fused silica capillary. Red blood cells (RBC) were migrated faster than white blood cells (WBC) and blood pellets to the direction of propagation of laser light. The observed photophoretic velocity of RBC was about 11 times faster than those of others. This was understood from the larger photophoretic efficiency of RBC than that of WBC, which was simulated based on the Mie scattering theory. Furthermore, it was found that, during the photophoretic migration, RBCs spontaneously orientated parallel to the migration direction so as to reduce the drag force. Finally, it was demonstrated that RBC and WBC were separated in a micro-channel flow system by the laser photophoresis.     

Preparation of β-Seleno-α,β-Unsaturated Nitroalkenes Via A Sulfur-Selenium Exchange Reaction

Several β-seleno-α,β-unsaturated nitroalkenes were prepared via an addition-elimination process using the corresponding sulfinyl compounds and phenyl or methyl selenol.     

Synthesis of 3,20-disubstituted chlorophyll-a derivatives and reactivity of the substituents

Methyl 20-bromo-pyropheophorbide-a possessing a vinyl group at the 3-position and its analogs having 3-ethyl, 3-(1-hydroxyethyl) and 3-acetyl groups were prepared by modifying naturally occurring chlorophyll(Chl)-a. The 20-bromo-chlorins were cross-coupled with vinyl- and 1-ethoxyvinyl-tributyltins in the presence of a Pd(0) catalyst to afford 20-vinyl- and acetyl-chlorins, respectively. The interconversions among the above four C2-functional groups at the 3-position were readily performed in the semi-synthetic Chl derivatives, but no modification of the 20-vinyl and acetyl groups was observed. The difference of the chemical reactivity is ascribable to the steric factor: the 3¹-position was less sterically hindered than the 20¹-position. Single hydrogenation and hydration of 3,20-divinyl-chlorin and reduction of 3,20-diacetylchlorin proceeded exclusively at the 3-position. The redmost (Qy) bands in electronic absorption spectra of the semi-synthetic Chl derivatives in a diluted dichloromethane solution were controlled by the 3,20-substituents. The 3-substituent effect on their Qy maxima was determined by the electronic factor (their electronegativity), while the 20-substituent effect was primarily dependent on the steric factor (their local size).     

Low-temperature reduction of silver(I) oxide particles with long chain alcohol

The mechanism of reducing silver(I) oxide particles to silver metals was studied using myristyl alcohol as a reducing agent. The reduction temperature of silver oxide with myristyl alcohol decreased to 150 °C from the temperature of silver oxide in air, 400 °C. The reduction temperature was decreased by myristyl alcohol reacting with silver oxide, which was confirmed by our reaction equation model obtained by gas chromatography determination, pyrolysis gas chromatography–mass spectrometry, and Karl Fischer titration. An endothermic of 153.7 kJ mol^?1 in the reduction of silver oxide with myristyl alcohol calculated from the reaction model using Hess’s law was coincident with that obtained experimentally by differential scanning calorimetry measurements.     

Erratum to: Comprehensive interrogation of electrochemical reaction and energy conversion of a direct fucose fuel cell

Journal of Solid State Electrochemistry - In this research, we conducted a comprehensive interrogation of a direct fucose fuel cell to maximise the electric power and demonstrated the potential for...     

Physicochemical Studies of Demetalation of Light-harvesting Bacteriochlorophyll Isomers Purified from Green Sulfur Photosynthetic Bacteria

Demetalation kinetics of bacteriochlorophylls (BChls) c, d and e from green sulfur photosynthetic bacteria were studied under weakly acidic conditions. Demetalation rate constants of BChl e possessing a formyl group at the 7-position were significantly smaller than those of BChls c and d , which had a methyl group at this position. The activation energy of demetalation of 3¹ R -8,12-diethyl([E,E])-BChl e was 1.5-times larger than that of 3¹ R -[E,E]-BChl c . ¹⁵N-labeled 3¹ R -[E,E]-BChls c and e were purified from cells of green sulfur bacteria grown in a medium containing ¹⁵NH₄Cl, and their ¹⁵N NMR spectra were measured. The chemical shifts of N₂₁, N₂₂ and N₂₃ atoms of 3¹ R -[E,E]-BChl e were lower-field shifted than those of 3¹ R -[E,E]-BChl c , respectively, and especially the difference in chemical shifts of N₂₂ was significantly large. These results suggest that the electron-withdrawing formyl group at the 7-position of BChl e affected an electronic state of the chlorin macrocycle and caused BChl e to be more tolerant for removal of the central magnesium compared with BChls c and d .