Insertion of pyridine into an iron-silicon bond: structure of the product Cp*(CO)Fe[eta3(C,C,C)-C5H5NSiMe2NPh2

Heating a toluene solution of Cp*(CO)(C5H5N)FeSiMe2NPh2 led to insertion of pyridine into the iron-silicon bond to form Cp*(CO)Fe[eta3(C,C,C)-C5H5NSiMe2NPh2].     

Studies on penem and carbapenem. I. Syntheses and oral absorption of ester-type prodrugs of sodium (5R,6S)-2-(2-fluoroethylthio)-6-[(1R)-1-hydroxyethyl]penem-3-c arboxylat e

Acyloxyalkyl esters (2a-d), alkyloxycarbonyloxyalkyl esters (2e-g) and (5-methyl-2-oxo-1,3-dioxol-4-yl)methyl ester (2h) of (5R,6S)-2-(2-fluoroethylthio)-6-[(1R)-1-hydroxyethyl]penem-3- carboxylic acid (1) were synthesized. Enhanced oral absorption was observed in mice reflecting increased lipophilicity, compared with the parent 1 itself. Among them, the ester 2h showed a prolonged plasma level and a large area under the blood concentration-time curve (AUC) in rats. These ester-type prodrugs of penem 1 in phosphate buffer (pH 6.86) were much more stable than those of cephalosporins which easily degraded via isomerization to delta 2 cephalosporins.     

Solution of large configuration mixing matrices arising in partitioning technique and applications to the generalized eigenvalue problem

A method is presented that can be used (a) to determine the several lowest eigenvalues and eigenvectors of large symmetric matrices, (b) to solve the generalized eigenvalue problem associated with energy-dependent operators, that arises in computations involving energy-dependent many-body Green's functions and in the evaluation of the true parameters of the effective valence shell hamiltonian, and (c) to directly evaluate the matrices associated with resolvent operators. The applicability to large configuration mixing calculations arises when the N-electron basis functions can be easily broken down to a few dominant configurations (the primary block) and their complement. Using the partitioning technique, the effective hamiltonian within the primary block is directly evaluated. The method is extended to evaluation of the dynamical polarizability tensor, which effectively contains the contributions from all of the eigenstates of a hamiltonian matrix, without the necessity of explicitly calculating its eigenvalues and eigenvectors.     

Synthesis and analgesic activity of novel heterocycles, [1]benzothiopyrano[3,4-b]pyrrole derivatives

In order to develop analgesic compounds possessing a sulfur atom in the alicyclic ring, novel cis-fused heterocycles, [1]benzothiopyrano[3,4-b]pyrrole derivatives (II) were synthesized via a unique cyclization reaction starting from 4-(4-methoxyphenylthio)-2-butanone (1) or 6-methoxy-3,4-dihydro-2H-1-benzothiopyran-4-one (7). The analgesic effects of benzothiopyranopyrroles (16, 18) were measured by means of the writhing test. The phenolic derivative 18 completely inhibited the appearance of writhing at the dose of 50 mg/kg, but the methoxy derivative 16 had no analgesic effect.     

Preparation,crystal structure,and spectroscopic,chemical, and electrochemical properties of (2E,4E)-1,4-di(3-guaiazulenyl)-1,3-butadiene compared with those of (E)-1,2-di(3-guaiazulenyl)ethylene

Wittig reaction of (E)-3-(3-guaiazulenyl)propenal (11) with (3-guaiazulenylmethyl)triphenylphosphonium bromide (9) in ethanol containing NaOEt at 25 °C for 24 h under argon gives the title new (2E,4E)-1,3-butadiene derivative 4, in 33% isolated yield, which upon treatment with hexafluorophosphoric acid (i.e., 65% HPF₆ aqueous solution) in tetrahydrofuran (=THF) at 25 °C for 1 h under aerobic conditions affords a new air (two-electron) oxidation product (E)-ethylene-1,2-bis(3-guaiazulenylmethylium) bis(hexafluorophosphate) (14), quantitatively, and further, zinc-reduction of 14 in trifluoroacetic acid (=CF₃COOH) at 0 °C for 1 h under argon reverts 4, quantitatively. Along with the above interesting results, our discovered another preparation method, spectroscopic properties, crystal structure, and electrochemical behavior of 4, which serves as a strong two-electron donor and acceptor, compared with those of the previously reported (E)-1,2-di(3-guaiazulenyl)ethylene (3) are documented in detail.     

Oxidation of sulfides with hydrogen peroxide catalyzed by synthetic flavin adducts with dendritic bis(acylamino)pyridines

The catalytic activities of the cationic synthetic flavin adduct 1 with various dendritic and non-dendritic 2,6-bis(acylamino)pyridines 2 were examined for the oxidation of organic sulfides with H₂O₂. The adduct of 5-ethyllumiflavinium perchlorate 1a with 2b–d bearing poly(benzyl ether) dendron units acts as an efficient organocatalyst for the oxidative transformation of sulfides to the corresponding sulfoxides under mild conditions.     

Annihilation rates of positrons on aromatic molecules

We have measured positron annihilation rates for a selection of hydrocarbon molecules based on six carbon atoms, including substituted benzenes. These measurements illustrate the importance of molecular symmetry in determining the annihilation rate.     

Inclusive η production at high pT at the ISR

The inclusive η production cross section at the CERN ISR has been measured for p_T values of up to 11 GeV/c. We find that the $\text{η}\text{π}{}^0$ cross-section ratio has an average value of 0.55 ± 0.07 and varies little with p_T.     

QCLDB—Quantum chemistry literature data base—a trial

A brief account of a quantum chemistry literature data base (QCLDB ) is described, which contains the key information of about 2000 papers of ab initio calculations of atoms and molecules published in 1977–1979. The QCLDB is stored in a computer and can be sorted and rearranged into author and substance indices. Selection of the items for each paper in a computer-readable data base is discussed.