The Absolute Configurations and Biogenesis of Some New Halogenated Chamigrenes from the Sea Hare Aplysia dactylomela

Four new halogenated chamigrenes have been isolated from the sea hare, the (E)- and (Z)-9-(bromomethylidene)-1,2,5-trimethylspiro[5.5]undeca-1,7-dien-3-ones ( 11 and 10 , resp.) the structures of which were deduced by NMR spectroscopy and by comparison with a known relative, the (8R,9R)-8-bromo-9-chloro-5,5,9-trimethyl-1-methylidenespiro[5,5]undec-3-en-2-one ( 12 ), and its (11 R)-11-acetoxy-substituted derivative 13 . Their structures and absolute configurations were determined and deduced by X-ray using the absolute-structure parameter. The configurations were remarkable in being enantiomeric to those of the tertiary chlorochamigrenes isolated so far. Consequently, a more general scheme is proposed to account for their biogenesis.     

Effekt von Cu(II)-Ionen auf die Magnetitbildung einer aus Eisen-II- und Eisen-III-hydroxid bestehenden Mischung

Ohne Zusammenfassung Herrn Dr.T. Katsurai danken wir für Anregung zu dieser Arbeit und hilfreiche Diskussion.     

Hamiltonian for the orbitals of general multiconfigurational self consistent field wave functions

The variational conditions for the orbitals of general multiconfigurational SCF wave functions are coupled in a unique way to construct a one-electron Hamiltonian with which one can determine all the occupied orbitals. Properties and application of the one-electron Hamiltonian in the relativistic framework are also discussed.     

Collision-induced desorption in 193-nm photoinduced reactions in (O2+CO) adlayers on Pt(112)

The spatial distribution of desorbing O(2) and CO(2) was examined in 193-nm photoinduced reactions in O(2)+CO adlayers on stepped Pt (112)=[(s)3(111)x(001)]. The O(2) desorption collimated in inclined ways in the plane along the surface trough, confirming the hot-atom collision mechanism. In the presence of CO(a), the product CO(2) desorption also collimated in an inclined way, whereas the inclined O(2) desorption was suppressed. The inclined O(2) and CO(2) desorption is explained by a common collision-induced desorption model. At high O(2) coverage, the CO(2) desorption collimated closely along the (111) terrace normal.     

In vitro replication study of modified bases in ras sequences.

DNA templates containing a modified base (O6-methylguanine, 8-hydroxyguanine, xanthine or hypoxanthine) which was located in nucleotide sequences corresponding to the 12th or 61st codon of a ras gene were synthesized and deoxynucleotide incorporation opposite the lesions was investigated. The templates were replicated by Taq DNA polymerase, recombinant rat DNA polymerase beta and mouse DNA polymerase alpha-primase complex. Sequence analysis of the replicated products indicated selective incorporation of nucleotide(s) opposite a modified base, depending on the kind of base and of DNA polymerase. This system is very useful to obtain results of in vitro replication of modified bases in ras sequences.     

Nano-aquarium with microfluidic structures for dynamic analysis of Cryptomonas and Phormidium fabricated by femtosecond laser direct writing of photostructurable glass

We demonstrate fabrication of microchips with microfluidic structures for dynamic analysis of living cells using a femtosecond (fs) laser. Fs laser direct writing followed by annealing and successive wet etching in dilute hydrofluoric (HF) acid solution resulted in formation of three dimensional (3D) hollow microstructures embedded in photostructurable glass. The embedded microchannel structure enabled us to analyze unique phenomenon of Cryptomonas, which suddenly swims very fast under certain condition. Vector analysis of the driving force for the rapid motion was also carried out by introducing nano-beads into the microchannel, in which Cryptomonas was encapsulated. We also fabricated a microchip for observation of Phormidium moving toward a seedling root, which accelerates growth of the seedling. Using the embedded microchannel in the microchip, observation of Phormidium assemblage to the seedling root was easily carried out. Such microchips with microfluidic structures, referred to as a nano-aquarium, realize the efficient and highly functional observation of living cells.     

Surface species studied by angle-resolved product desorption: Emission mechanism and spatial distribution

Recent progress and future developments in angle-resolved measurements of desorbing surface reaction products are reviewed for the analysis of surface species. Spatial and energy distributions of desorbing products with hyperthermal energy deliver the most direct structural information of the transition state including active intermediates and product formation sites. Knowledge of the desorption mechanism is requisite to achieve structural information since the method is directly linked to the chemical process. Structural analyses are exemplified in photoinduced O₂ desorption and CO oxidation, and compared with those from thermal N₂O decomposition and CO oxidation as well as their applications to steady-state catalytic processes.     

Room temperature observation of nitric oxide on Ir(1 1 1) by scanning tunneling microscopy

Room temperature (RT) adsorption of nitric oxide (NO) on Ir(1 1 1) was studied by scanning tunneling microscopy (STM). At low exposures, NO molecules can not be imaged by STM, because at RT the diffusion of NO is much faster than the STM scanning speed. At high exposures near the saturation coverage, however, a well-ordered 2 × 2 structure is observed. The coverage of the major 2 × 2 species is 0.25 and they can be assigned to the NO molecules adsorbed on the Ir ontop sites. A small number of less bright spots are assigned to nitrogen atoms produced by dissociation. Their number increases by annealing the NO-saturated surface at 380 K. A small number of another dissociation product, oxygen, are observed as black lines, indicating that the diffusion of oxygen atoms is fast. Scratch-like noise features were also detected by the STM, which suggests that a mobile precursor state exists, which was clearly shown by the effects of electron irradiation from the STM tip. These results are consistent with the previous molecular beam studies. Hopping of the 2 × 2 ordered NO species was frequently observed at the anti-phase domain boundaries and edges of the 2 × 2 islands.     

Revisiting [3 + 3] route to 1,3-cyclohexanedione frameworks: hidden aspect of thermodynamically controlled enolates.

We have revisited the traditional consecutive Michael-Claisen [3 + 3] process (MC-[3 + 3]) promising the synthesis of a cyclohexane-1,3-dione derivatives from nonactivated simple ketones and enoates and evaluated its potential in modern organic synthesis. Twenty to thirty examples were demonstrated to be effective. The reactions exhibited remarkable regioselectivity with the Michael addition proceeding through nucleophilic attack by the more hindered site of the ketones without exception. The subsequent Claisen condensation resulted in the formation of carbon-carbon bonds between less hindered site of the ketones and acyl carbon of the enoates. The MC-[3 + 3] process described is useful for the synthesis of Taxol A-ring synthons in multigram quantities and for the synthesis of other six-membered carbocyclic compounds. A number of control experiments have been conducted to provide strong support for the mechanism of this MC-[3 + 3].