Ruthenium-catalyzed formation of aryl(diphenyl)phosphine oxides by reactions of propargylic alcohols with diphenylphosphine oxide

1,1-Diaryl-1-penten-4-yn-3-ols react with diphenylphosphine oxide in the presence of a thiolate-bridged diruthenium complex as a catalyst and give high yields of aryl(diphenyl)phosphine oxide products via an initial substitution followed by a cyclization at the produced allene intermediate. [reaction: see text]     

Double phosphinylation of propargylic alcohols: a novel synthetic route to 1,2-bis(diphenylphosphino)ethane derivatives

[reaction: see text] Double phosphinylation of propargylic alcohols with diphenylphosphine oxide in the presence of a thiolate-bridged diruthenium complex as catalyst gives the corresponding 2,3-bis(diphenylphosphinyl)-1-propenes in high yields with a complete selectivity.     

Asymmetric synthesis of axially chiral benzamides and anilides by enantiotopic lithiation of prochiral arene chromium complexes

Axially chiral benzamides and anilides were prepared by enantiotopic lithiation at the distinguished benzylic methyl of prochiral tricarbonylchromium complexes of N,N-diethyl 2,6-dimethylbenzamide (1) and N-methyl-N-acyl 2,6-dimethylaniline (14 and 21) with a chiral lithium amide base followed by electrophilic substitution in good yields with high optical purity. The resulting axially chiral chromium-complexed benzamides and anilides were oxidized under air to give chromium-free axially chiral benzamides and anilides in an enantiomerically active form without axial bond rotation at room temperature.     

Ni(II)- and Co(II)-phosphine complex catalyzed carboncarbon bond formation between organic tellurides and grignard reagents

Treatment of alkenyl and aryl tellurides with Grignard reagents in the presence of NiCl₂(PPh₃)₂, NiCl₂(Ph₂PCH₂CH₂CH₂PPh₂), or CoCl₂(PPh₃)₂ as catalyst affords the cross-coupling products together with the homo-coupling products of the tellurides in good to moderate yields under mild conditions.     

Detection of bilayer packing stress and its release in lamellar-cubic phase transition by time-resolved fluorescence anisotropy

An introduction of nonlamellar-forming lipids into planar bilayers generates packing stress, which is important for the biological functions of plasma membranes and is a driving force for the lamellar-nonlamellar phase transition. We have investigated the phase behavior of a binary system consisting of egg yolk phosphatidylcholine and monoolein (MO) and the changes in the local orientation order of lipids in a lamellar-bicontinuous cubic phase transition. Small-angle X-ray scattering has revealed that the lamellar-bicontinuous cubic phase transition occurs at an MO molar fraction (X(MO)) between 0.6 and 0.7. These phases were dispersed to form liposomes and cubosomes to monitor the anisotropy of the incorporated fluorescence probe, in which Pluronic F127, used as a dispersion stabilizer of the cubic phase, has been proven not to alter the cubic structure and the location of the probes. Time-resolved fluorescence anisotropy measurements on these dispersions have revealed that the order parameter of the probe in the lamellar phase increases with increasing X(MO), and that it decreases during the transition to the cubic phase. This observation suggests that packing stress generated by the addition of the nonlamellar-forming lipid is released by the phase transition.     

Fabrication of high performance thin films from metal fluorocomplex aqueous solution by the liquid phase deposition

The hetro-structured oxide thin films from metal fluorocomplex solution have been prepared by the liquid phase deposition (LPD) method. The Pt/Nb₂O₅ and Au/Nb₂O₅ composite films can be prepared from a mixed solution of niobium source, H₃BO₃, Pt(NH₃)₄Cl₂ and HAuCl₄ aqueous solutions under the ambient temperature and atmosphere. In the case of Au/SiO₂ composite film, (NH₄)₂SiF₆ solution is used as a mother solution. The Pt and Au ionic species are deposited in Nb₂O₅ and SiO₂ matrices. They are reduced to their metallic state after treatment above 200 °C. The size of dispersed particles can be controlled by heat treatment temperature. It is also clear that, gold nanoparticles are also found to interact with SiO₂, although the interaction is smaller than that with Nb₂O₅ showing the size of Au nanoparticles remain smaller in Nb₂O₅ that in SiO₂.     

First asymmetric total synthesis of tetrodotoxin

Tetrodotoxin, a toxic principle of puffer fish poisoning, is one of the most famous marine natural products because of the complex structure having many functional groups and its potent biological activity leading to death. Since the structure elucidation in 1964, this toxin has been recognized as a formidable target molecule for total synthesis. We have recently achieved the first asymmetric total synthesis from 2-acetoxy-tri-O-acetyl-d-glucal as a chiral starting material. The highly hydroxylated cyclohexane ring was constructed by Claisen rearrangement and regioselective hydroxylations of an acetone moiety and an intramolecular directed aldol condensation of the precursor having methyl ketone with dihydroxyacetone, which was synthesized through Sonogashira coupling. Installation of nitrogen functionality was unsuccessful through an attempted Overman rearrangement. We, therefore, employed a new intramolecular conjugate addition strategy between the carbamate and unsaturated ester groups. The alpha-hydroxyl lactone moiety was synthesized through an intramolecular epoxide opening by the Z-enolate of aldehyde, which was followed by oxidation-reduction of the resulting cyclic vinyl ether. The lactone was then converted to a protected ortho ester, and then gunanidinylation was followed by cleavage of the 1,2-glycol to give the fully protected tetrodotoxin. Selection of the protective groups has finally led us to accomplish the total synthesis of tetrodotoxin in an enantiomerically pure form. All the stereogenic centers were controlled with high selectivity, and the hydroxyl groups were differently protected to discriminate for the future analogue synthesis of a bioorganic program. The synthetic tetrodotoxin was purified by ion exchange chromatography and characterized to be identical with the natural compound.     

Requirement for radiation shields of transportation pipe for on line inhalation gases from compact cyclotron in positron emission tomography

In the unit housing of a compact cyclotron and positron emission CT (PET), positron emitting gas such as 15O, 11C, C15O2, C15O etc. is supplied from a cyclotron to a PET room through a transportation pipe with an appropriate shield to reduce positron annihilation radiation. Using lead or concrete shield blocks with various thicknesses, radiation leakage through the shield was measured by an ionization chamber type survey meter during continuous and constant supply of 15O gas of 1.85 GBq/min concentration which is the maximum dose for clinical use. The leakage radiation measured was 213.7, 56.0, 15.3, 5.0 muSv/week for lead shield with 1, 2, 3, and 4 cm thickness, respectively, and 193.3, 30.5 and 5.1 muSv/week for concrete shields with thickness of 10, 20, and 30 cm, respectively. The present study shows that to keep less than 300 muSv/week, which is the permissible dose rate of the boundary zone around the radiation controlled area by Japan Science and Technology Agency, it is required to use more than 8 mm thick lead shield or 7 cm thick concrete for continuous supply of 1.85 GBq/min 15O gas.     

Self-assembly patterning of colloidal crystals constructed from opal structure or NaCl structure

We developed a novel self-assembly process to fabricate an orderly array of particle wires constructed from a close-packed colloidal crystal without preparation of patterned templates. A substrate was immersed vertically into a SiO2 colloidal solution, and the liquid surface moved downward upon evaporation of solution. Particles formed a mono-/multiparticle layer, which was cut by the periodic drop-off of solution. The orderly array of particle wires was successfully fabricated, showing the suitability of the self-assembly process for the fabrication of nano-/microstructures constructed from nano-/microparticles or blocks. The mechanism of the assembly process and control of thickness, width, and interval of particle wires were further discussed. Moreover, an array of particle wires constructed not from close-packed face-centered cubic (or hexagonal close packed) structure but from two kinds of particles was realized to fabricate an array of particle wires with NaCl structure by this self-assembly process.     

Synthesis of Urea‐Tethered Disaccharides in Water

A new method for the synthesis of urea‐linked disaccharides in aqueous media has been developed. The key feature of our approach is two strained Steyermark‐type gluco‐ and galactopyranosyl oxazolidinones. Each oxazolidinone is attached to a pyranose ring in a di‐equatorial trans‐annulation framework. Reaction of these oxazolidinones with 4‐aminohexopyranose in water proceeded smoothly to afford the urea‐tethered cellobiose and lactose analogues. The galactose‐type oxazolidinone proved to be more reactive than the glucose‐type, which is explained by the presence of an axial hydroxy group at C4 in the former.