Our search for highly active hydrogenation catalysts for carbonyl compounds, starting with neutral Rh(I) hydride complexes, [RhH(PR3)n] (R=i-Pr, n=3; R=Cy, n=2), has led to the discovery of cationic Rh(I) complexes with fully alkylated diphosphine ligands, [Rh{(i-Pr)2P(CH2)nP(i-Pr )2}(NBD)]C104 (n=3,4). These compounds prove to be versatile and efficient for hydrogenation of a variety of carbonyl compounds, including aldehydes.A number of rhodium complexes, e.g., neutral rhodium(I) complexes of Wilkinson type, [RhXL3] (L=triarylphosphines) and cationic rhodium(I) complexes containing an aryl-substituted diphosphines, were found to be active catalysts for olefin hydrogenation.)) These metal complexes, however, are not very active for ketone hydrogenation.)) An enhancement of the activity of rhodium complex catalysts was observed on the addition of strong alkali, i.e., [RhCI(C8H12)(PPh3)]-NaBH4-KOH2a) or [RhCl2(bpy)2]Cl-NaOH.2b) In this paper we wish to report that the catalytic activity of rhodium(I) species for hydrogenation of carbonyl compounds can be markedly improved with electron-donating fully alkylated phosphines.Our principal strategy was to increase the electron density of the metal center by utilizing the electron-donating trialkylphosphines together with a hydrido ligand. Since [RhH{P(i-Pr),},]their activity was tested for several ketones (Table 1). The results were encouraging.[RhH(PCy3)2] was even active for PhCOPh which could not readily be hydrogenated by Osborn's system, [Rh-(PPhMe2)H2(S)2]+-H20 (S=solvent), under ambient conditions. 4) This is rather remarkable since the Rh(I) hydride containing triarylphosphine, e.g., [RhH(DBP)4] (DBP=5-phenyl-5H-dibenzophosphole) is known to be totally inactive as a hydrogenation catalyst for ketones.5) Table 1 also includes results of transfer hydrogenation of some ketones effected with [RhHhexanone is mainly (94%) trans-4-tert-butylcyclohexanol in contrast to the predominant formation of the cis-product effected by IrCl6 -P(OMe)3 in acidic medium.6) In the latter case an incipient protonation of the carbonyl oxygen atom may probably be involved, followed by the hydride transfer to the less hindered carbonyl face. The predominant formation of trans-alcohol in the present case suggests an extensive thermodynamic control which in turn implies a rapid reverse the overall catalytic rate with Rh(I) complexes of monodentate trialkylphosphines should have been impaired by rapid dehydrogenation of the product alcohol.
緒言連続鋳造鋳片の中心偏析や大型鋳塊の
・河嶋 佳純3)
・谷川 英司3)
・大笹 憲一
1) Evaluation of Permeability for Columnar Dendritic Structures by Three Dimensional Numerical Flow AnalysisYukinobu Natsume, Daiki takahashi, Kasumi kawashima, Eiji taNigawa and Kenichi Ohsasa Synopsis : Toevaluatethepermeabilityforcolumnardendriticstructures,threedimensional(3D)flowsimulationsofinterdendriticliquidwerecarried out. The 3D columnar dendrites were made by means of the computer aided design (CAD), which were based on two-dimensional dendrite morphologiescalculatedbyaphase-fieldmethod.Theartificial3Dcolumnardendriteswereregularly-arranged,andsixkindsof3Dcolum-nardendriticstructureswereobtained,whichhavedifferentvolumefractionsofliquidbetween0.56and0.95.Forthesecolumnardendritic structures,theflowsparallelandnormaltotheprimarydendritearmswerecalculatedbytheFLUENT,andthepermeabilityforsix3Dco-lumnardendriticstructuresandbothflowdirectionsweredeterminedbyusingtheDarcylaw
A new model that can quantitatively evaluate the permeability for columnar dendritic structures was developed by modifying the Kozeny constant in Kozeny-Carman's equation. The modified Kozeny constant consists of two terms: one accounting for the flow direction for primary arms of columnar dendrites and the other accounting for the tortuosity of channels in the dendritic structures. The permeability calculated by this new model was compared with that obtained in our previous simulations [Y. Natsume et al.: Tetsuto-Hagané, 99 (2013), 117] and from experiments other researchers [K. Murakami et al.: Acta metall., 31 (1983), 1417, 32 (1984), 1423, Liu et al.: Mater. Sci. Tech., 5 (1989, 1148] and the values were found to be in fairly good agreement with the compared values. In addition, we investigated the obtained quantitative model to determine permeability for use in computational studies of macrosegregation. To evaluate the permeability quantitatively using Kozeny-Carman's equation, the value of the specific surface area for dendrites is required. We introduced an assumption that the inverse of the specific surface area for columnar dendrites is proportional to the secondary arm spacing. By using this assumption in our modified model, the permeability can be determined using only the dendrite arm spacing and liquid volume fraction.
A genetic transformation system was developed for the selective white rot basidiomycete
Ceriporiopsis subvermispora
using a modified protocol with polyethylene glycol and CaCl
2
treatment of the protoplasts and plasmids harboring recombinant hygromycin phosphotransferase (
hph
) driven by a homologous promoter. During repeated transfer on fresh potato dextrose agar plates containing 100 µg/ml hygromycin B, most transformants lost drug resistance, while the remaining isolates showed stable resistance over five transfers. No drug-resistant colonies appeared in control experiments without DNA or using a promoter-less derivative of the plasmid, indicating that a transient expression of the recombinant
hph
was driven by the promoter sequence in these unstable drug-resistant transformants. Southern blot analysis of the stable transformants revealed random integration of the plasmid DNA fragment in the chromosome at different copy numbers. This transformation system yielding mostly transient transformants was successfully used for promoter assay experiments, and only a 141-bp fragment was found to be essential for the basic promoter function of glyceraldehyde dehydrogenase gene (
gpd
) in this fungus. Subsequent mutational analyses suggested that a TATAA sequence is important for the basic promoter function of
gpd
gene. The promoter assay system will enable the functional analysis of gene expression control sequences quickly and easily, mostly in the absence of undesirable effects from differences in copy number and chromosomal position of an integrated reporter gene among stable transformants.
Respiratory syncytial virus (RSV) is one of the most common causes of lower respiratory tract infections and a significant pathogen for both adults and children. Although two drugs have been approved for the treatment of RSV infections, the low therapeutic index of these drugs have led pharmaceutical companies to develop safe and effective small-molecule anti-RSV drugs. The pyrazolo[1,5-a]pyrimidine series of compounds containing a piperidine ring at the 2-position of the pyrazolo[1,5-a]pyrimidine scaffold are known as candidate RSV fusion (F) protein inhibitor drugs, such as presatovir and P3. The piperidine ring has been revealed to facilitate the formation of an appropriate dihedral angle between the pyrazolo[1,5-a]pyrimidine scaffold and the plane of the amide bond for exertion of anti-RSV activity. A molecular-dynamic study on newly designed compounds with an acyclic chain instead of the piperidine ring proposed and demonstrated a new series of pyrazolo[1,5-a]pyrimidine derivatives, such as 9c with a 1-methyaminopropyl moiety, showing similar dihedral angle distributions to those in presatovir. Compound 9c exhibited potent anti-RSV activity with an EC 50 value of below 1 nM, which was similar to that of presatovir. A subsequent optimization study on the benzene ring of 9c led to the potent RSV F protein inhibitor 14f with an EC 50 value of 0.15 nM. The possibility of improving the biological properties of anti-RSV agents by modification at the 7-position of pyrazolo[1,5-a]pyrimidine is also discussed.
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