The roles of hetero atoms in solvolytic reactions—II: Transannular participation by neighbouring sulphur atom

Esters of sulphur-containing 5- and 6-membered heterocycles, tetrahydro-3- and 4-thiopyranol and their 3- and 4-methyl, phenyl derivatives, and tetrahydro-2-thiophenemethanol, were synthesized. The solvolysis of β-thioesters in 80% aqueous acetone resulted in strong transannular S-participation and the products of solvolysis substantiated formation of bicyclic episulphonium ion intermediates. Such participation is considered to be present even in a tertiary system. On the other hand, γ-thioesters were solvolysed without any transannular S-participation,     

A quantum chemical study of interchain hopping model of negatively charged solitons in polyacetylene

Phonon-assisted interchain hopping of negatively charged solitons in polyacetylene has been studied using a local chemical reaction model CH + CH₄ → CH₄ + CH. Quantum chemical characteristics of the electron transfer process have been analyzed in terms of the dynamic electron density and the mutual polarization moment. The CH stretching vibrational motion of CH₄, which is a local model of the sp³ defect, has been found to play a significant role for the electron transfer. The excitation of the corresponding vibrational mode of the sp³ defect would promote the interchain hopping of the charged soliton. The electron transfer process has also been studied in terms of the “regional” density functional theory. It has been shown that the driving force of the electron transfer is represented by the regional chemical potentials.     

A comparison of b and uds quark jets to gluon jets

Symmetric three-jet events are selected from hadronic Z⁰ decays such that the two lower energy jets are each produced at an angle of about 150° with respect to the highest energy jet. In some cases, a displaced secondary vertex is reconstructed in one of the two lower energy jets, which permits the other lower energy jet to be identified as a gluon jet through anti-tagging. In other cases, the highest energy jet is tagged as a b jet or as a light quark (uds) jet using secondary vertex or track impact parameter and momentum information. Comparing the two lower energy jets of the events with a tag in the highest energy jet to the anti-tagged gluon jets yields a direct comparison of b, uds and gluon jets, which are produced with the same energy of about 24 GeV and under the same conditions. We observe b jets and gluon jets to have similar properties as measured by the angular distribution of particle energy around the jet directions and by the fragmentation functions. In contrast, gluon jets are found to be significantly broader and to have a markedly softer fragmentation function than uds jets. For thek _⊥ jet finder withy _cut=0.02, we find as the ratios of the mean charged particle multiplicity in the gluon jets compared to the b and uds jets. Results are also reported using the cone jet finder.     

Measurement of the hadronic decay current in τ?→π??+vτ

The properties of hadronic Z⁰ decays with final state photons, measured with OPAL at LEP, have been compared with predictions from two different matrix element calculations ofO( _s ). Two calculations, GNJETS and EEPRAD, have been investigated which use different schemes to restrict the phase space around the poles of the cross section. Assuming the E0-JADE jet definition, both calculations describe the data well in large regions of phase space fory _cut values around 0.06. For very large and very small jet-photon masses some deviations from the predictions have been found, indicating the importance of higher order corrections. Significant differences between the calculations are only apparent in the predicted rate of 1-jet plus photon events. The rate is higher in GNJETS which reproduces the data better than EEPRAD.     

Cisplatin suppository: preparation, release characteristics and clinical evaluation

Cisplatin (CDDP) has attracted attention as a chemotherapeutic agent for the treatment of uterine endometrial carcinoma but causes serious side effects, including renal toxicity. CDDP suppositories containing NaCl at different concentrations were prepared to enhance the efficacy and to reduce the side effects of CDDP. The release characteristics, melting point and viscosity of the suppositories were first studied. The rate of CDDP release increased as the NaCl concentration increased: it was 12% 12 h after administration of suppositories containing no NaCl, but 32% with 0.2% NaCl. The melting point was raised by addition of NaCl: 35.5 degrees C without NaCl and 36.5 degrees C with 0.2% NaCl. Addition of 0.2% NaCl doubled the viscosity. Clinically, the suppository containing 0.06% NaCl was given to 3 patients with endometrial carcinoma twice a week for 3 weeks to examine serum CDDP levels and endometrial absorption. Patients with endometrial carcinoma showed different peak plasma platinum (Pt) levels which were as low as 0.12, 0.06 and 0.22 micrograms Pt/ml with similar patterns of change in the level. Radiographic analysis revealed many Pt particles in sections of necrosed endometria after 21d of the treatment. No side effects of CDDP were found in biochemical testing or subjective symptoms.     

Emission of 2-phenylethanol from its β-d-glucopyranoside and the biogenesis of these compounds from [H8] l-phenylalanine in rose flowers

The hydrolysis of 2-phenylethyl β-d-glucopyranoside (3) was found to be partially inhibited by feeding with 2-phenyl-N-glucosyl-acetamidiumbromide (8), a β-glucosidase inhibitor, resulting in a decrease in the diurnal emission of 2-phenylethanol (2) from Rosa damascena Mill. flowers. Detection of [1,1,2,2′,3′,4′,5′,6′-²H₈]-2 and [1,2,2′,3′,4′,5′,6′-²H₇]-2 from R. ‘Hoh-Jun’ flowers fed with [1,1,2,2′,3′,4′,5′,6′-²H₈]-3 suggested that β-glucosidase, alcohol dehydrogenase, and reductase might be involved in scent emission. Comprehensive GC-SIM analyses revealed that [1,2,2,2′,3′,4′,5′,6′-²H₈]-2 and [1,2,2,2′,3′,4′,5′,6′-²H₈]-3 must be biosynthesized from [1,2,2,2′,3′,4′,5′6′-²H₈] l-phenylalanine ([²H₈]-1) with a retention of the deuterium atom at α-position of [²H₈]-1.     

Isolation,chemical characterization and structure of ansamitocin,a new antitumor ansamycin antibiotic

In this paper we report the isolation, chemical characterization and structural elucidation of Ansamitocin, a new antitumor antibiotic obtained from Nocardia No. C-15003 (N-1). Ansamitocin P-3, P-3' and P-4 with molecular formulae C₃₂H₄₃ClN₂O₉, C₃₂H₄₃ClN₂O₉ and C₃₃H₄₅ClN₂O₉, respectively, were identified as novel antibiotics. Their UV spectra resemble that of maytansine obtained from a plant source. Analysis of the PMR spectrum and spin-decoup studies of P-3 demonstrated that its skeletal structure was the same as that of maytansine. Reductive cleavage of each antibiotic gave maytansinol (P-0). Alkali hydrolysis of P-3, P-3' and P-4 gave isobutyric, butyric and isovaleric acids, respectively. P-3, P-3' and P-4 were concluded to be the isobutyrate, butyrate and isovalerate ester of maytansinol at C-3, respectively. An antitumor plant product, maytanacine, and its semisynthetic derivative, maytansinol propionate, were also produced by the same strain.     

Double percolation effect on the electrical conductivity of conductive particles filled polymer blends

Electrical conductivity of carbon black (CB) filled polymer blends which are incompatible with each other was studied as a function of the polymer's blend ratio. Transmission electron microscope (TEM) analysis shows that CB distributes unevenly in each component of a polymer blend. TEM photographs of phase structure of solvent extracted HDPE/PMMA blend and solvent extraction experiments of PMMA/PP blend detect the blend ratio at which the structural continuity of filler rich phase is formed. The electrical conductivity of polymer blends is found to be determined by two factors. One is the concentration of CB in the filler rich phase and the other is the structural continuity of this phase. This double percolation affects the conductivity of conductive particle filled polymer blends.     

Tin(II)-Based Metal–Organic Frameworks Enabling Efficient,Selective Reduction of CO2 to Formate under Visible Light

Certain metal complexes are known as high-performance CO₂ reduction photocatalysts driven by visible light. However, most of them rely on rare, precious metals as principal components, and integrating the functions of light absorption and catalysis into a single molecular unit based on abundant metals remains a challenge. Metal-organic frameworks (MOFs), which can be regarded as intermediate compounds between molecules and inorganic solids, are potential platforms for the construction of a simple photocatalytic system composed only of Earth-abundant nontoxic elements. In this work, we report that a tin-based MOF enables the conversion of CO₂ into formic acid with a record high apparent quantum yield (9.8 % at 400 nm) and >99 % selectivity without the need for any additional photosensitizer or catalyst. This work highlights a new MOF with strong potential for photocatalytic CO₂ reduction driven by solar energy.     

Dehydration‐fragmentation mechanism of cathinones and their metabolites in ESI‐CID

Various cathinone‐derived designer drugs (CATs) have recently appeared on the drug market. This study examined the mechanism for the generation of dehydrated ions for CATs during electrospray ionization collision‐induced dissociation (ESI‐CID). The generation mechanism of dehydrated ions is dependent on the amine classification in the cathinone skeleton, which is used in the identification of CATs. The two hydrogen atoms eliminated during the dehydration of cathinone (primary amine) and methcathinone (secondary amine) were determined, and the reaction mechanism was elucidated through the deuterium labeling experiments. The hydrogen atom bonded to the amine nitrogen was eliminated with the proton added during ESI, in both of the tested compounds. This provided evidence that CATs with tertiary amine structures (such as dimethylcathinone and α‐pyrrolidinophenones [α‐PPs]) do not undergo dehydration. However, it was shown that the two major tertiary amine metabolites (1‐OH and 2″‐oxo) of CATs generate dehydrated ions in ESI‐CID. The dehydration mechanisms of the metabolites of α‐pyrrolidinobutiophenone (α‐PBP) belongs to α‐PPs were also investigated. Stable‐isotope labeling showed the dehydration of the 1‐OH metabolite following a simple mechanism where the hydroxy group was eliminated together with the proton added during ESI. In contrast, the dehydration mechanism of the 2″‐oxo metabolite involved hydrogen atoms in three or more locations along with the carbonyl group oxygen, indicating that dehydration occurred via multiple mechanisms likely including the rearrangement reaction of hydrogen atoms. These findings presented herein indicate that the dehydrated ions in ESI‐CID can be used for the structural identification of CATs.