Liquid-liquid extraction of copper(I) by cyclic tetrathio ethers

The liquid-liquid extraction of copper(I) with 12-, 13-, 15- and 16-membered cyclic tetrathio ethers ([n]aneS₄, where n represents the total number of carbon and sulphur atoms in the cyclic ligand ring) was examined stoichiometrically using picrate ion (Pic^?) for the formation of the ion pair. Copper(I) was extracted with four ligands (L) into 1,2-dichloroethane as the ion-pair compound, [Cu(I)L]⁺Pic^?. The extraction constant, K_ex, with each ligand was determined. As the ring size of cyclic tetrathio ethers increases, the log K_ex values, including that previously reported for [14]aneS₄, increase from 7.7 to 9.4. The value of Δ log K_ex, which represents the increase in log K_ex due to the addition of one carbon atom to the macrocyclic ring, was large between [13]aneS₄ and [14]aneS₄ (Δ log K_ex=1.0) and small between [14]aneS₄ and [15]aneS₄ (Δ log K_ex=0.1).     

Comparative study of IBMK and DIBK as extraction solvents in strongly acidic media: extraction behaviour and kinetic stability of Cu(PCD)(2) in these solvents

The use of di-isobutyl ketone (DIBK) and isobutyl methyl ketone (IBMK) as the solvent for extraction of copper(II) from strongly acidic media (0.01-8M hydrochloric acid) with ammonium l-pyrrolidinecarbodithioate has been studied. In contrast to IBMK, the volume of the DIBK extract remains the same, irrespective of the acidity of the aqueous phase. A certain amount of free acid is transferred into both solvents, and affects the kinetic stability of the chelate extracted; the free acid can be completely removed by washing the extract with water, and partly by filtering it through a dry filter paper. However, the chelate extracted into DIBK exhibits excellent stability without such treatment, since the amount of free acid in DIBK is much smaller than that in IBMK. When DIBK is used, the copper chelate can be quantitatively extracted as long as the extraction is done from acidic media.     

Photoresponsive porphyrin-imprinted polymers prepared using a novel functional monomer having diaminopyridine and azobenzene moieties

A novel photoresponsive functional monomer bearing diaminopyridine and azobenzene moieties was synthesized and applied to the preparation of photo-regulated molecularly imprinted polymers, which can recognize porphyrin derivatives through hydrogen bonding. The binding affinity of the imprinted cavities was regulated by UV irradiation, suggesting that azobenzene groups located inside the binding sites worked as photosensitizers and the trans-cis isomerization could regulate the affinity for the target compounds. Repetitive binding of the target compound to trans-IP and cis-IP was directly monitored by slab optical waveguide spectroscopy and the photo-mediated regulation of binding affinity was successfully confirmed.     

Identification of a new excited state responsible for the in vivo unique absorption band of siphonaxanthin in the green alga Codium fragile

A marine green alga, Codium fragile, exhibits a characteristic in vivo absorption band of a specific keto-carotenoid, siphonaxanthin, at 535 nm. We examined the ultrafast fluorescence kinetics by direct excitation of this band after purification of light-harvesting complex II. On the basis of a high fluorescence anisotropy (0.39) up to 1 ps and a very short lifetime (60 fs), we identified the 535 nm band as a new electronically excited state (Sx) located between the S1 and S2 states. Excited-state dynamics of the Sx state were further discussed in relation to the energy transfer processes in the complexes.     

Studies on glycolipids. III. Glyceroglycolipids from an axenically cultured cyanobacterium, Phormidium tenue.

Seven new monogalactosyl diacylglycerols (1-7) and six new digalactosyl diacylglycerols (11-16) were isolated from an axenically cultured cyanobacterium, P. tenue. Their structures were elucidated on the basis of physicochemical evidence and the results of enzymatic hydrolysis using a lipase (from Rhizopus arrhizus). Comparison of antialgal activity for P. tenue between monogalactosyl diacylglycerols (1-8) and digalactosyl diacylglycerols (11-19) revealed that the former showed more potent activity than the latter.     

Studies on cardiac ingredients of plants. VII: Chemical transformation of proscillaridin by means of the Diels-Alder reaction and biological activities of its derivatives.

The Diels-Alder reactions of a cardiac glycoside, proscillaridin (1), with some dienophiles were investigated. The reaction of 1 with alkenes such as methyl vinyl ketone and methyl acrylate afforded 3-oxo-2-oxabicyclo[2.2.2]oct-7-enes (2-5) and para-substituted benzene derivatives (6 and 7), while 1 reacted with alkynes (3-butyn-2-one, methyl propiolate) to yield para- or meta-substituted benzene derivatives (6-9). The biological activities of the resulting derivatives were evaluated by the use of isolated guinea-pig papillary muscle preparations and Na+,K(+)-adenosine triphosphatase (ATPase) preparation from dog kidney. Among the proscillaridin derivatives, compounds 4 and 7 moderately inhibited Na+,K(+)-ATPase activity. Furthermore, the concentration range of 7 over which its positive inotropic effect on guinea-pig papillary muscle preparations, increased from 5% to 95% of maximum was broader than that of 1, i.e., concentration dependency was maintained over a greater range of concentration.     

Regio-selective cyanation of (Z)-(1,2-dibromo-2-arylvinyl)triisopropylsilane with suppression of halogen elimination

Highly regio-selective cyanation of vicinal (Z)-dibromoalkenyl silanes was achieved by a vinylic Rosenmund-von Braun reaction, significantly suppressing side-production of alkyne. The alkyne was generated by a halogen elimination side-reaction that is an intrinsic problem in metal-activation of vicinal dihaloalkenes. We have studied to overcome the problem, and finally found the combination of CuCN and O = PPh₃ in toluene solvent effectively controlled the production of byproducts. The resultant single isomer has significance in potentially application as a multi-tunable synthetic scaffold.     

Polymerization of optically active disubstituted acetylene monomers by Pd catalyst bearing bulky phosphine ligand

Chloro- and aryl-substituted acetylene monomers having an optically active group were polymerized by a Pd catalyst [(^tBu₃P)PdMeCl] bearing a bulky phosphine ligand, and by MoCl₅ for comparison. The corresponding disubstituted acetylene polymers with M_n's = 2000–19,500 and 6900–10,800 were obtained in 29–83% and 11–62% yields when the Pd and Mo catalysts were used, respectively. The formation of polyacetylenes, poly[(R)- 1p ], poly[(R)- 1m ], and poly[(S)- 2p ] were confirmed by SEC and the presence of a Raman scattering peak based on the alternating double bonds of the main chain. Pd-based poly[(R)- 1m ] exhibited CD signals around 350 nm assignable to a certain secondary structure, while Mo-based poly[(R)- 1m ] did not. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3011–3016