Cascade Rearrangement of 5-Cyclopentylidenecyclooctanones

Acid-catalyzed rearrangement of 5-cyclopentylidenecyclooctanone derivatives 9a-c was examined to obtain polyspiropolyquinanes 11a-c, considered to have a unique helical structure, through cascade rearrangement pathways consisting of continuous transannular cyclization followed by successive 1,2-alkyl shifts. The substrates were prepared easily by use of the Wittig or McMurry reaction. Reaction of the 5-cyclopentylidenecyclooctanone (9a) with acid gave the expected dispirotriquinane ketone 11a in high yield. The precise mechanism was elucidated by a deuterium-labeling experiment. In the case of the ketone 9b, having another spiroannulated cyclopentane ring attached on 9a, the trispirotetraquiane 11b was not obtained but the bis-propellane-type tetrahydrofuran 25 was produced exclusively. The 5-(5'-cyclopentylidenecyclooctylidene)cyclooctanone (9c) afforded the polycyclic compounds 27-31, depending on the acid used, instead of the desired tetraspiropentaquinane 11c. The structures of the products were determined by NMR spectral data including 2D (13)C INADEQUATE spectra and X-ray crystallographic analyses. The unexpected rearrangement pathways are also discussed.     

Efficient and widely applicable method of constructing neo-proteoglycan utilizing copper(I) catalyzed 1,3-dipolar cycloaddition

Efficient constructions of two types of neo-proteoglycan are described. Enzymatically prepared alkyne containing chondroitin 6-sulfate chains and chemically synthesized azido group having compounds are linked by utilizing the copper(I) catalyzed 1,3-dipolar cycloaddition.     

Isolation, characterization, and theoretical study of La2@C78

A new metallofullerene, La2@C78, has been synthesized by DC arc discharge method, isolated by high-performance liquid chromatography, and characterized by laser desorption time-of-flight mass spectrometry, UV-vis-NIR absorption, differential pulse voltammetry, 13C NMR spectroscopy, and theoretical calculations. The La2@C78/CS2 solution is dark violet and presents several characteristic absorption features at 647, 561, 533, and 386 nm, with an onset around 1000 nm. With respect to empty D3-C78, the capability of La2@C78 as an electron acceptor or donor is stronger. Addition of 1,1,2,2-tetrakis(2,4,6-trimethylphenyl)-1,2-disirane to La2@C78 photochemically, as well as thermally, affords bis- and mono-adducts. Theoretical studies and 13C NMR spectroscopic analysis of La2@C78 indicate that it possesses a D3h-C78 cage (78:5).     

Oscillating frequency of piezoelectric quartz crystal in solutions

Oscillating frequencies of a piezoelectric crystal were measured in various solutions. One side of the crystal surface was coated with a silicon sealant. This coating was useful for measuring the oscillation of crystals in solutions for a wide range of products of density (?) and viscosity (η) and in electrolyte solutions. For measurement in solutions, the frequency change depended on the circuit used, whereas for measurements in air the circuit did not influence the frequency change. All experimental data showed that the frequency change from pure water, ΔF_w, followed ΔF_w = ? K(√?η ? √?_wη_w) except for electrolyte and polymer solutions, where K is a proportionality constant, η_w the density of pure water and η_w the viscosity of water.     

Photocrosslinkable polyesters with conjugated double bonds: Reciprocity effect in laser recording

The reciprocity effect under intense illumination was studied with photocrosslinkable polyesters of p-phenylenebis(α-cyanobutadiene carboxylic acid) (I), m-phenylenebis(α-cyanobutadiene carboxylic acid) (II), and p-phenylenebis(acrylic acid) (III), with an argon ion laser as a light source. The reciprocal sensitivities of I, II, and III were 5.0, 1800, and > 10⁵ mJ/cm², respectively. II and III required sensitization to enhance their sensitivities to a level at which reciprocity effects could be measured. I obeyed the reciprocity law over a wide range of exposure times from seconds to microseconds. Both II′, a copolyester of II, and III showed a dramatic decrease of sensitivity in high-intensity/short-time exposure when sensitized by 9,10-phenanthraquinone and pyrylium salts.     

Asymmetric hydrogenation of chiral pyruvamides

Asymmetric catalytic hydrogenations of three kinds of chiral pyruvamides were carried out using palladium on charcoal as a catalyst to give lactamides with diastereomeric ratios ranging from 76:24 to 98:2.     

Synthesis of [5'-13C]ribonucleosides and 2'-deoxy[5'-13C]ribonucleosides

The present efficient synthesis of [5'-13C]ribonucleosides and 2'-deoxy[5'-13C]ribonucleosides is characterized by the synthesis of the D-[5-13C]ribose derivative as an intermediate via the Wittig reaction of 4-aldehydo-D-erythrose dialkyl acetals with Ph3P13CH3I-BuLi to introduce the 13C label at the 5-position of a pentose. This was followed by the highly diastereoselective osmium dihydroxylation for the preparation of 2,3-di-O-benzyl-D-[5-13C]ribose dialkyl acetal and the cyclization from D-[5-13C]ribose dialkyl acetal derivatives to the alkyl D-[5-13C]ribofuranoside derivative by the use of LiBF(4). The obtained D-[5-13C]ribose derivative was converted into [5'-13C]ribonucleosides and subsequently into the corresponding 2'-deoxynucleosides.     

Light emission from chlorine atoms formed in the dissociative excitation of HCI in a flowing afterglow of discharged argon

Light emission from Cl(5p) atoms (near 440 nm) produced in the reaction of HCl in a discharged flow of argon was investigated with a flowing-afterglow apparatus. Ionic species, most probably argon ions in metastable states, Ar^+M, were found to be responsible for the Cl(5p) production in the dissociative excitation of HCl.     

Polyhydrazides. III. N-methylated polyhydrazides by ring-opening of poly-p-phenylene-1,3,4-oxadiazole

A new ring-opening reaction of 1,3,4-oxadiazole by methylating reagents was developed in fuming sulfuric acid or polyphosphoric acid and then, by applying this reaction to poly-p-phenylene-1,3,4-oxadiazole, a high molecular weight poly-N-methylterephthalylhydrazide was obtained. Various methylating reagents were investigated as ring-opening reagents. The degrees of ring-opening in polymers were estimated and related to the properties of the polymers.     

Extraction of Catecholamines by Calixarene Carboxylic Acid Derivatives

Extraction behaviors of catecholamines with a series of calixarene carboxylic acid derivatives were investigated. Relatively large calix[6]arene and calix[8]arene extract catecholamines into the organic solution, while smaller calix[4]arene and the monomer analog do not. The calix[6]arene, which has a cavity that fits a protonated amino group well, selectively extracts a primary amino compound dopamine over other catecholamines. Slope analysis and Job’s method confirmed formation of a 1:1 complex between the calix[6]arene and dopamine. On the other hand, the calix[8]arene extracts both dopamine and adrenaline, due to the large cavity for induced-fit recognition. Dopamine extracted with the calixarene is quantitatively stripped by contacting the organic solution with a fresh acidic solution.