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131.
Hirofumi Maekawa 《Tetrahedron letters》2004,45(20):3869-3872
Mg-promoted reduction of a mixture of aromatic ketones (or imines) and aliphatic carbonyl compounds in N,N-dimethylformamide (DMF) brought about unique mixed pinacol type of cross coupling to give unsymmetrical vicinal diols (or amino alcohols) or α-hydroxyketones in good to moderate yields. The reaction may be initiated by electron transfer from magnesium metal to an aromatic carbonyl compound possessing a less negative reduction potential. The difference of reduction potential between aromatic ketones (or imines) and aliphatic carbonyl compounds was found to be one of the important key factors in this selective cross coupling. 相似文献
132.
Hydrodesulfurization activity of cobalt Chevrel phase sulfide catalysts has been investigated in a fixed-bed flow reactor.
Single phase cobalt Chevrel phase sulfides exhibited catalytic activity for hydrodesulfurization. Supported cobalt Chevrel
phase sulfides catalysts indicated much higher hydrodesulfurization activity and even higher than commercial CoMoS/Al2O3 catalysts. The existence of Mo6S8 and the reduced oxidation state of Mo in the cobalt Chevrel phase sulfides has been observed by XRD, LRS, and XPS.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
133.
Magno Agostinho Andrei Banu Pierre Braunstein Richard Welter Xavier Morise 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(3):m81-m86
Three new palladium complexes containing a difunctional P,N‐chelate, namely tris(chloro{[1‐methyl‐1‐(6‐methyl‐2‐pyridyl)ethoxy]diphenylphospine‐κ2N,P}methylpalladium(II)chloroform solvate, 3[Pd(CH3)Cl(C21H22NOP)]·CHCl3, (III), dichloro[2‐(2,6‐dimethylphenyl)‐6‐(diphenylphosphinomethyl)pyridine‐κ2N,P]palladium(II), [PdCl2(C26H24NP)], (IV), and chloro[2‐(2,6‐dimethylphenyl)‐6‐(diphenylphosphinomethyl)pyridine‐κ2N,P]methylpalladium(II), [Pd(CH3)Cl(C26H24NP)], (V), are reported. Geometric data and the conformations of the ligands around the metal centers, as well as slight distortions of the Pd coordination environments from idealized square‐planar geometry, are discussed and compared with the situations in related compounds. Non‐conventional hydrogen‐bond interactions (C—H⋯Cl) have been found in all three complexes. Compound (III) is the first six‐membered chloro–methyl–phosphinite P,N‐type PdII complex to be structurally characterized. 相似文献
134.
Fujimoto H Pinak M Nemoto T O'Neill P Kume E Saito K Maekawa H 《Journal of computational chemistry》2005,26(8):788-798
Clustered DNA damage sites induced by ionizing radiation have been suggested to have serious consequences to organisms, such as cancer, due to their reduced probability to be repaired by the enzymatic repair machinery of the cell. Although experimental results have revealed that clustered DNA damage sites effectively retard the efficient function of repair enzymes, it remains unclear as to what particular factors influence this retardation. In this study, approaches based on molecular dynamics (MD) simulation have been applied to examine conformational changes and energetic properties of DNA molecules containing clustered damage sites consisting of two lesioned sites, namely 7,8-dihydro-8-oxoguanine (8-oxoG) and apurinic/apyrimidinic (AP) site, located within a few base pairs of each other. After 1 ns of MD simulation, one of the six DNA molecules containing a clustered damage site develops specific characteristic features: sharp bending at the lesioned site and weakening or complete loss of electrostatic interaction energy between 8-oxoG and bases located on the complementary strand. From these results it is suggested that these changes would make it difficult for the repair enzyme to bind to the lesions within the clustered damage site and thereby result in a reduction of its repair capacity. 相似文献
135.
o-Dibromoacetylbenzophenone, 2 or o-bromoacetylbenzophenone 3 reacted with aqueous ammonia to produce 3-phenylisoindolin-1-one 5. The reaction of 3 with methylamine afforded 3-hydroxy-2-methyl-3-phenyl-isoindolin-1-one 4 and 2-methyl-3-phenylisoindolin-1-one 5. Whereas from 2 with methylamine only 5 was obtained. 相似文献
136.
The 1,3-dipolar cycloaddition of polymer-supported azomethine ylides to dipolarophiles gave pyrrolidine derivatives in good yields. The azomethine ylides were generated from resin-bound alpha-silylimines via a 1,2-silatropic shift. The features of this method are not only a traceless synthesis but also a unique solid-phase route to pyrrolidines with extensive diversity. [reaction: see text] 相似文献
137.
Hamamoto H Anilkumar G Tohma H Kita Y 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(23):5377-5383
The oxidative intramolecular coupling reaction of phenol ether derivatives (nonphenolic derivatives) on treatment with a novel combination of a hypervalent iodine(III) reagent, phenyliodine bis(trifluoroacetate) (PIFA), and heteropoly acid (HPA) was studied. Biaryl compounds were obtained in excellent yields on treatment of highly substituted phenol ethers. On the other hand, spirodienones were specifically formed when one of the preferred arylic coupling sites was substituted with a methoxy group in the para position. 相似文献
138.
Prof. Dr. Hiroshi Tanaka Maasa Yamanouchi Haruko Miyoshi Keisuke Hirotsu Prof. Dr. Hirofumi Tachibana Prof. Dr. Takashi Takahashi 《化学:亚洲杂志》2010,5(10):2231-2248
We report on the solid‐phase synthesis of a combinatorial methylated (±)‐epigallocatechin gallate (EGCG) library and its biological evaluation. Epigallocatechin gallate (EGCG) and its methylated derivatives, which are members of the catechin family, exhibit various anti‐cancer effects. The solid‐phase synthesis of methylated EGCG involves the preparation of the α‐acyloxyketone by the coupling of a solid‐supported aldehyde with a ketone and an acid. The subsequent release and reductive etherification reaction of the solid‐supported α‐acyloxyketone provide the protected EGCG in good total yields. Sixty‐four methylated EGCGs were successfully prepared. The growth‐inhibitory effects of the methylated EGCG library were also examined. Although methylation of EGCG generally causes reduced growth inhibition, the growth‐inhibitory effect of 7‐OMe EGCGs was comparable to that of EGCG. The 7‐OMe EGCGs are attractive drug candidates because of their enhanced bioavailability. 相似文献
139.
Harusawa S Murai Y Moriyama H Imazu T Ohishi H Yoneda R Kurihara T 《The Journal of organic chemistry》1996,61(13):4405-4411
A synthetic route to 4(5)-(beta-D-ribofuranosyl)imidazole (1), starting from 2,3,5-tri-O-benzyl-D-ribose (5), was developed via a Mitsunobu cyclization. Reaction of 5 with the lithium salt of bis-protected imidazole afforded the corresponding 5-ribosylimidazole 7RS. Hydrolysis of 7RS gave a 1:1 mixture of diol isomers 8R and 8S having an unsubstituted imidazole. Mitsunobu cyclization of the mixture 8RS using N,N,N',N'-tetramethylazodicarboxamide and Bu(3)P exclusively afforded benzylated beta-ribofuranosyl imidazole 9beta in 92% yield, accompanied by alpha-anomer 9alpha, in a ratio of 26.3:1. The configuration of 9beta was established by X-ray crystallography of ethoxycarbonyl derivative 10beta. Reductive debenzylation of 9beta over Pd/C was carried out, and the synthesis of 1 was attained from starting 5 in four steps and 87% overall yield. This synthetic methodology was extended to the synthesis of 4(5)-(2-deoxy-beta-D-ribofuranosyl)imidazole (2). Mitsunobu cyclization of a 1:1 mixture of the corresponding diol isomers 14RS produced 15beta and 15alpha in a ratio of 5.4:1. The synthesis of 2 was attained in a 59% overall yield from the starting 3,5-di-O-benzyl-2-deoxy-D-ribose (12). beta-Stereoselective glycosylation in the key step is discussed and explained by intramolecular hydrogen bonding between an NH in the imidazole and the oxygen functional group in the sugar moiety. 相似文献
140.
Takeuchi H Nagira S Tanimura S Yamamoto H Kawashima Y 《Chemical & pharmaceutical bulletin》2005,53(5):487-491
We attempted to make the rapidly dissolving tablet (Tab) containing solid dispersion particles (SD) with indomethacin (IMC) and porous silica (Sylysia350) as carrier prepared by using spray-drying technique. Rapidly dissolving tablet was formulated with mannitol as a diluent and low substituted hydroxypropylcellulose (L-HPC) or partly pre-gelatinized starch (PCS) as a disintegrant. The percent dissolved from Tab (SD) was higher than that of tablet containing physical mixture (PM) at 20 min. Nearly 100% of drug in Tab (SD) was dissolved within 60 min, while the drug dissolution of Tab (PM) was not completed at the same time period. In addition, the tensile strength of Tab (SD) was much higher than that of Tab (PM). Adding L-HPC in Tab (SD) (Tab (SD-L-HPC)), the percent dissolved from Tab (SD-L-HPC) at 5 min became much higher than that from Tab (SD). The dissolution profile of IMC from Tab (SD-L-HPC) was almost the same irrespective of the compression pressure, while the tensile strength of tablet increased with increasing the compression pressure. In comparing the compaction property of these tablets by observing the ratio of residual die wall pressure (RDP) to maximum die wall pressure (MDP) (RDP/MDP), it was found that addition of L-HPC in the tablet formulation improved compactibility. In case that PCS was formulated as disintegrant, Tab (SD-PCS), similar improvement in the dissolution profile and tensile strength was observed, though the dissolution rate of IMC from Tab (SD-PCS) was slightly lower than that from Tab (SD-L-HPC) irrespective of the compression pressure. 相似文献