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ABSTRACT: An efficient synthetic method was developed for the construction of enantiomerically pure trans-3-arylpiperazine-2-carboxylic acid derivatives using diaza-Cope rearrangement (DCR) as a key step starting from (R,R)/(S,S)-1,2-bis(2-hydroxyphenyl)-1,2-diaminoethane (HPEN). A complete transfer of stereochemical integrity was observed for the transformation. Piperazine ring formation from the chiral 1,2-ethylenediamine derivatives using diphenylvinylsulfonium triflate followed by oxidation using ruthenium(III) chloride monohydrate in the presence of sodium periodate provided the desired enantiopure trans-3-arylpiperazine-2-carboxylic acid derivatives.
Organic Letters 07/2012; · 5.86 Impact Factor
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Chemistry - An Asian Journal 08/2011; 6(8):1921-5. · 4.50 Impact Factor
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ABSTRACT: Hepatocellular carcinoma (HCC) is frequently associated with abnormalities in cell cycle regulation, leading to increased activity of cyclin-dependent kinases (Cdks) due to the loss, or low expression of, Cdk inhibitors. In this study, we showed that ibulocydine (an isobutyrate prodrug of the specific Cdk inhibitor, BMK-Y101) is a candidate anti-cancer drug for HCC. Ibulocydine has high activity against Cdk7/cyclin H/Mat1 and Cdk9/cyclin T. Ibulocydine inhibited the growth of HCC cells more effectively than other Cdk inhibitors, including olomoucine and roscovitine, whereas ibulocydine as well as the other Cdk inhibitors and BMK-Y101 minimally influenced the growth of normal hepatocyte cells. Ibulocydine induced apoptosis in HCC cells, most likely by inhibiting Cdk7 and Cdk9. In vitro treatment of HCC cells with ibulocydine rapidly blocked phosphorylation of the carboxyl-terminal domain (CTD) of the large subunit of RNA polymerase II, a process mediated by Cdk7/9. Anti-apoptotic gene products such as Mcl-1, survivin, and X-linked IAP (XIAP) are crucial for the survival of many cell types, including HCC. Following the inhibition of RNA polymerase II phosphorylation, ibulocydine caused rapid down-regulation of Mcl-1, survivin, and XIAP, thus inducing apoptosis. Furthermore, ibulocydine effectively induced apoptosis in HCC xenografts with no toxic side effects. These results suggest that ibulocydine is a strong candidate anti-cancer drug for the treatment of HCC.
Journal of Biological Chemistry 06/2011; 286(22):19662-71. · 4.77 Impact Factor
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ABSTRACT: A simple gram-scale synthesis of Pd-Fe(3)O(4) heterodimer nanocrystals was achieved by controlled one-pot thermolysis of a mixture solution composed of iron acetylacetonate, palladium acetylacetonate, oleylamine, and oleic acid. The heterodimer nanocrystals are composed of a 6 nm-sized Pd nanosphere and a 30 nm-sized faceted Fe(3)O(4) nanocrystal and they are soft ferrimagnetic with high saturation magnetization value and low coercivity value. The heterodimer nanocrystals exhibited good activities for various Suzuki coupling reactions. Furthermore, the nanocrystal catalyst could be easily separated from the product mixture by using a magnet and could be recycled 10 times without losing catalytic activity.
Physical Chemistry Chemical Physics 02/2011; 13(7):2512-6. · 3.57 Impact Factor
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ABSTRACT: A simple synthesis of Rh-Fe(3)O(4) heterodimer nanocrystals was achieved by controlled one-pot thermolysis. The nanocrystals exhibited excellent activities for the selective reduction of nitroarenes and alkenes. Furthermore the nanocrystal catalyst could be easily separated by a magnet, and recycled eight times without losing the catalytic activity.
Chemical Communications 02/2011; 47(12):3601-3. · 6.17 Impact Factor
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ABSTRACT: Peptide deformylase (PDF), which removes the formyl group at the N-terminal methionine residue of nascent protein, has been recognized as a potent target for antibacterial therapy. We report herein the synthesis and structure-activity relationship studies of non-peptide PDF inhibitors.
Bioorganic & medicinal chemistry letters 01/2011; 21(1):133-6. · 2.65 Impact Factor
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ABSTRACT: Peptide deformylase (PDF) is a metalloprotease catalyzing the removal of a formyl group from newly synthesized proteins. Thus inhibition of PDF activity is considered to be one of the most effective antibiotic strategies. Reported herein are the synthesis and structure-activity relationship studies of retro-amide inhibitors based on actinonin, a naturally occurring PDF inhibitor. Analysis of the structure-activity relationships led to the discovery of 7a, which exhibits potent enzyme inhibition and antibacterial activity against Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis.
Bioorganic & medicinal chemistry letters 08/2010; 20(15):4317-9. · 2.65 Impact Factor
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ABSTRACT: Hepatocellular carcinoma (HCC) frequently includes abnormalities in cell cycle regulators, including up-regulated cyclin-dependent kinase (Cdks) activities due to loss or low expression of Cdk inhibitors. In this study, we show that xylocydine, a cyclin-dependent kinase (Cdk) specific inhibitor, is a good anti-cancer drug candidate for HCC treatment. Xylocydine (50muM) selectively down-regulates the activity of Cdk1 and Cdk2, accompanied by significant cell growth inhibition in HCC cells. Xylocydine also strongly inhibits the activity of Cdk7 and Cdk9, in vitro as well as in cell cultures, that is temporally associated with apoptotic cell death in xylocydine-induced HCC cells. This is associated with inhibition of phosphorylation of RNA polymerase II at serine residues 5 and 2, which are targets of Cdk7 and Cdk9, respectively. The effects on apoptosis are concomitant with changes in the levels of anti-apoptotic proteins, Bcl-2, XIAP, and survivin, which are markedly down-regulated, and pro-apoptotic molecules, p53 and Bax, which are elevated in HCC cells after treatment with xylocydine. The up-regulated level of p53 was associated with increased stability of the protein, as levels of Ser15 and Ser392 phsophorylated p53 are similarly elevated in the inhibitor treated cells. We demonstrated that xylocydine can effectively suppress the growth of HCC xenografts in Balb/C-nude mice by preferentially inducing apoptosis in the xenografts, whereas the drug did not cause any apparent toxic effect on other tissues. Taken together, these data suggest that the novel Cdk inhibitor xylocydine is a good candidate for an anti-cancer drug for HCC therapy.
Cancer letters 08/2009; 287(2):196-206. · 4.86 Impact Factor
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ABSTRACT: Sixteen diphenylethylenediamine analogues including those with electron donating, electron withdrawing, and sterically bulky substituents have been prepared in good overall yields (70-90%) and in enantiomerically pure form (>99% ee) by diaza-Cope rearrangement reaction. A single chiral mother diamine, ((R,R)-1,2-bis-(2-hydroxyphenyl)-1,2-diaminoethane), is reacted with appropriate aldehydes to form the initial diimines that rearrange to give all the product diimines in the (S,S) form. The daughter diamines are obtained by hydrolysis of the product diimines. Density functional theory computation shows that resonance-assisted hydrogen-bond is the main driving force behind all the rearrangement reactions. Chiral high performance liquid chromatography and circular dichroism spectroscopy show that the highly stereospecific rearrangement reactions take place with apparent inversion of stereochemistry.
Journal of the American Chemical Society 10/2008; 130(36):12184-91. · 9.91 Impact Factor
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ABSTRACT: An efficient asymmetric synthesis of 6-aminobicyclo[2.2.1]heptane-2-carboxylic acid as a novel gamma-turn mimic has been achieved. Structural analysis of the gamma-amino acid derivative was carried out using (1)H NMR spectroscopy and intramolecular hydrogen bonding between side chain amides confirmed the turn structure, which had been predicted by Ab initio computational study.
Protein and Peptide Letters 02/2008; 15(9):980-4. · 1.94 Impact Factor
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ABSTRACT: Novel heterocyclic ring-substituted pyrimidines have been designed as inhibitors of glycogen synthase kinase-3beta (GSK-3beta) from the modification of known inhibitors. Several potent inhibitors exhibiting nanomolar activities were discovered against GSK-3beta kinase as well as in an NF-kappaB reporter gene assay. Based on the results from in vitro TNF-alpha release inhibition and in vivo endotoxima, these inhibitors are expected to be useful candidates for treatment of inflammation-related diseases.
Bioorganic & medicinal chemistry letters 02/2008; 18(2):653-6. · 2.65 Impact Factor
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ABSTRACT: Zn(II) complex of L (N,N'-bis(2-pyridylmethyl)-N,N'-dimethyl-trans-1,2-diaminocyclohexane) binds chiral vicinal diamines (1,2-diphenylethylenediamine (dpen) and 1,2-diaminocyclohexane (dach)) stereoselectively. Crystallographic studies reveal that the ternary complex has the C2 symmetric cis-alpha topology. 1H NMR shows that the R,R form of the tetradentate zinc complex binds rapidly and reversibly to the R,R form of the diamine over the S,S form with a stereoselectivity of about 5:1. Although the diamine exchange rate is rapid it is slower than the NMR time scale, and distinct signals for the diastereomeric complexes are observed when racemic mixtures of the host and guest molecules are mixed. Origin of stereoselectivity is discussed in terms of steric effects.
The Journal of Organic Chemistry 12/2006; 71(23):8966-8. · 4.45 Impact Factor
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Advanced Synthesis & Catalysis 01/2006; 348(1‐2):41 - 46. · 6.05 Impact Factor
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ABSTRACT: A cobalt(III)-salen complex (3) with an axial substituent on the diamine backbone has been synthesized. Crystal structure reveals that the axial substituent (p-nitrophenyl group) is positioned in close proximity to the metal binding site. The stereoselectivity of the cobalt complex for binding amino alcohols increases with increasing steric bulk of the amino alcohol from alaninol (2.9) to valinol (6.2) and t-leucinol (36.0).
Journal of the American Chemical Society 01/2006; 127(48):16776-7. · 9.91 Impact Factor
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ABSTRACT: A chiral pyrrolidinylmethanol derivative containing perfluoro-ponytails (5) was prepared from (S)-proline. The use of this perfluoro-substituted amino alcohol in catalytic asymmetric additions of organozinc reagents to aldehydes affords products with high enantioselectivities in both pure hexane and a mixture of hexane and FC-72 (perfluorohexane). Enantiomeric excesses up to 94 and 88 % ee have been achieved in Et(2)Zn and Ph(2)Zn additions, respectively. For the reactions in the biphasic solvent system a striking temperature effect was observed. Thus, when the temperature was raised from 0 to 40 degrees C the ee value of the product increased from 81 to 92 %. Furthermore, the catalyst loading could be remarkably low, and with only 0.1 mol % of amino alcohol 5 a product with 90 % ee was obtained in the Et(2)Zn addition to benzaldehyde in hexane. The perfluoro-ligand was easily recovered by simple phase separation, and until the ninth repetition its reuse proceeded without significant loss of enantioselectivity and reactivity.
Chemistry 02/2005; 11(3):945-50. · 5.93 Impact Factor
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ABSTRACT: New chiral hydroxyethers 1a-f were prepared for asymmetric protonation of achiral enolates prepared from prochiral ketones. The enantioselectivity of protonation was highly dependent upon the acidity of the chiral alcohols, the highest enantioselectivity (90% ee) being achieved with 3,5-dichloro-substituted beta-hydroxyether 1c. A salt-free enolate generated from trimethylsilyl enol ether 4 provided product of the highest ee. Unlike other reagents, chloro-substituted alcohols provided almost consistent enantioselections throughout the reaction temperatures examined (-25 to -98 degrees C). Protonation of other aromatic ketones showed selectivity similar to that of 2-methyl-1-tetralone.
The Journal of Organic Chemistry 08/2004; 69(15):5104-7. · 4.45 Impact Factor
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ABSTRACT: Catalytic allylation of aldehydes and the synthesis of homoallylic amines using bismuth sulfonate immobilized on silica gel in presence of allyltributylstannane are reported for the first time. The reaction proceeds smoothly with the aid of benzoic acid as an additive and provides corresponding homoallylic alcohols and homoallylic amines in good yields. The catalyst can be reused five times without significant loss of the catalytic activity.Bismuth Sulfonate Immobilized on Silica gel for Allylation of Aldehydes and Synthesis of Homoallylic Amines.
Catalysis Letters 06/2004; 96(3):201-204. · 2.24 Impact Factor
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ABSTRACT: Various imidazolium ionic liquids such as [Bmim]PF6, [Bmim]SbF6, [Bmim]OTf and [Bmim]BF4 were screened for recycling an organic catalyst [(5S)-5-benzyl-2,2,3-trimethylimidazolidin-4-one (1)] for asymmetric Diels–Alder reactions. Good yields and enantioselectivies (up to 85% yield and 93% ee) were obtained from reactions in [Bmim]PF6 or [Bmim]SbF6. However, reactions in [Bmim]OTf or [Bmim]BF4 gave racemic products in low yields. Isolation of the products by simple extraction using diethyl ether allowed recycling of the ionic liquid containing the immobilized catalyst in subsequent reactions without significant decrease of yields and enantioselectivities.
Advanced Synthesis & Catalysis 02/2004; 346(1):49 - 52. · 6.05 Impact Factor
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ABSTRACT: Catalytic allylation of carbonyl compounds in water using tetraallyltin in the presence of lanthanum sulfonate immobilized on mesoporous silica (SBA-15) has been carried out for the first time. The reaction proceeded smoothly in water and furnished the corresponding homoallylic alcohols in good to excellent yields. The catalyst could be reused without significant loss of catalytic activity.
Advanced Synthesis & Catalysis 08/2003; 345(8):936 - 938. · 6.05 Impact Factor
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ABSTRACT: Threefold parallel interwoven (6,3) nets were assembled from Ni(II) cyclam complex and 1,3,5-tris[2-(4-carboxyphenyl)-1-ethynyl]benzene. The network generates triangular voids of effective size ca. 18.4 x 14.7 x 9.5 A. It contains 35% free volume of the crystal volume and is stable up to 300 degrees C.
Inorganic Chemistry 03/2003; 42(3):676-8. · 4.60 Impact Factor
