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ABSTRACT: The reaction of propargylic carbonates with 4-hydroxy-2-pyrones in the presence of a palladium catalyst is described. By the choice of the reaction temperature, two types of the substituted furo[3,2-c]pyran-4-one derivatives were regioselectively synthesized, respectively.
The Journal of Organic Chemistry 01/2013; · 4.45 Impact Factor
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ABSTRACT: A novel and highly diastereoselective intramolecular carbamoylketene/alkene [2 + 2] cycloaddition has been developed, and the methodology was successfully applied to the enantioselective syntheses of (-)-esermethole and Takayama's intermediate for (+)-psychotrimine.
Organic Letters 12/2012; · 5.86 Impact Factor
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ABSTRACT: This'll fix it: Efficient fixation of atmospheric CO(2) has been achieved by the reaction of propargylic amines with a silver/DBU dual-catalyst system. Various oxazolidinones were synthesized in moderate to good yields by using substituted propargylic amines.
Chemistry 11/2012; · 5.93 Impact Factor
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ABSTRACT: Total synthesis of debromoflustramines B and E has been accomplished by using a platinum-catalyzed addition reaction of o-aminophenylboronic acid with the allene and an intramolecular carbamoylketene-alkene [2 + 2] cycloaddition for the construction of the basic carbon framework of the target alkaloids as the key steps.
The Journal of Organic Chemistry 09/2012; 77(20):9240-9. · 4.45 Impact Factor
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ABSTRACT: A full account of the development of a novel type of the intramolecular Hosomi-Sakurai reactions of the substrates with a p-benzoquinone and an allylsilane moieties connected by an ether linkage is described. This transformation proceeds via an addition-elimination sequence and provides the products with two stereogenic centers through a 1,3(or 1,4)-asymmetric induction in good to excellent diastereoselectivities. A reasonable mechanistic possibility for the reaction, determination of the stereochemistry for the product, and scope and limitation of the transformation are also discussed. The methodology developed here can successfully be applied to the enantiocontrolled total synthesis of the natural enantiomers of (-)-heliespirone A and (+)-heliespirone C, which have been isolated from sunflower Helianthus annuus L. as allelochemicals.
The Journal of Organic Chemistry 08/2012; 77(18):8231-43. · 4.45 Impact Factor
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ABSTRACT: An enantioselective synthesis of 8-epi-xanthatin (9) has been accomplished starting from the bicyclic lactone 3, which has been used for the synthesis of other xanthanolides, sundiversifolide (4) and diversifolide (5), through a synthetic route without the use of a selenium species. Additionally we have evaluated antimicrobial activities of five natural xanthanolides and their derivatives. Although the synthetic xanthanolides did not show any activity against methicillin-resistant Staphylococcus aureus (MRSA), some of the synthetic intermediates did exhibit moderate antimicrobial activities.
Chemical & pharmaceutical bulletin 07/2012; 60(10):1340-2. · 1.70 Impact Factor
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Chemistry 02/2012; 18(6):1604-7. · 5.93 Impact Factor
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ABSTRACT: The first total synthesis of penostatin B has been accomplished by using a highly diastereoselective Pauson-Khand reaction and an efficient relay ring-closing metathesis for the construction of the basic carbon skeleton of the natural product as the key steps.
Organic Letters 12/2011; 14(1):244-7. · 5.86 Impact Factor
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ABSTRACT: The second-generation enantioselective total synthesis of aspergillide C, a new type of 14-membered macrolide isolated from a marine-derived fungus, has been accomplished in a longest linear sequence of 15 steps from a chiral building block in 19% overall yield employing the 6-exo-trig transannular oxy-Michael reaction as the key step.
Chemical Communications 07/2011; 47(26):7440-2. · 6.17 Impact Factor
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ABSTRACT: The reaction of propargylic acetates with 2-oxocyclohex-3-enecarboxylates in the presence of a palladium catalyst is described. Substituted 7-methylenebicyclo[3.2.1]oct-3-en-2-ones were synthesized in a highly diastereoselective manner.
Organic Letters 07/2011; 13(13):3482-5. · 5.86 Impact Factor
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ABSTRACT: The reaction of 2-alkynyl-1-azaspiro[2.3]hexanes with a platinum catalyst is described. 1,4,5,6-Tetrahydrocyclopenta[b]pyrroles having a variety of substituents were conveniently synthesized via a cascade cyclization/ring-expansion process.
The Journal of Organic Chemistry 06/2011; 76(14):5813-20. · 4.45 Impact Factor
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Satoshi Kawashima,
Takenori Yamamoto,
Yuka Horiuchi,
Kengo Fujiwara,
Shunichi Gouda,
Yuya Yoshimura,
Atsushi Yamamoto,
Yuki Inotani,
Kikuji Yamashita,
Seiichiro Kitamura,
Hiroshi Terada,
Makoto Kanematsu, Kozo Shishido,
Yasuo Shinohara
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ABSTRACT: A recent report has described that S-15176 (N-[(3,5-di-tert-butyl-4-hydroxy-1-thiophenyl)]-3-propyl-N'-(2,3,4-trimethoxybenzyl) piperazine), an anti-ischemic agent, inhibits the mitochondrial permeability transition (PT) induced by not only Ca(2+) and inorganic phosphate, but also by tert-butylhydroperoxide or phenylarsine oxide [Morin et al. (Biochem Pharmacol 72:911-918, 2006)]. In the present study, we tested the effects of S-15176 on the PT induced by Ag(+), PT of which is not suppressed by cyclosporin A or oligomycin. S-15176 was effective in suppressing the PT and the subsequent cytochrome c release induced by Ag(+), and hence, it was concluded to be a more universal PT inhibitor than cyclosporin A or oligomycin. In addition to the PT-suppression activity, S-15176 also showed weak protonophoric activity. Thus, we further tested to investigate whether the hydroxyl group of S-15176 was involved in its PT-suppression or weak protonophoric activities. The methylated derivative of S-15176 also showed both PT suppression and weak protonophoric activities; hence, the hydroxyl group of S-15176 was concluded not to be involved in these activities.
Molecular and Cellular Biochemistry 06/2011; 358(1-2):45-51. · 2.06 Impact Factor
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ABSTRACT: Enantiocontrolled total syntheses of the breviones A, B, and C have been accomplished using a highly diastereoselective oxidative coupling of an α-pyrone with a tricyclic diene prepared from an optically pure Wieland-Miescher ketone derivative through the 7-endo-trig mode of acyl radical cyclization.
Journal of the American Chemical Society 06/2011; 133(23):8854-7. · 9.91 Impact Factor
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Angewandte Chemie International Edition 03/2011; 50(11):2618-20. · 13.45 Impact Factor
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Yuya Horinouchi,
Koichiro Tsuchiya,
Chiaki Taoka,
Soichiro Tajima,
Yoshitaka Kihira,
Yuko Matsuda, Kozo Shishido,
Masahiro Yoshida,
Shuichi Hamano,
Kazuyoshi Kawazoe,
Yasumasa Ikeda,
Keisuke Ishizawa,
Shuhei Tomita,
Toshiaki Tamaki
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ABSTRACT: Recently, increasing evidence suggests that the antihypertensive drug nifedipine acts as a protective agent for endothelial cells, and that the activity is unrelated to its calcium channel blocking. Nifedipine is unstable under light and reportedly decomposes to a stable nitrosonifedipine (NO-NIF). NO-NIF has no antihypertensive effect, and it has been recognized as a contaminant of nifedipine. The present study for the first time demonstrated that NO-NIF changed to a NO-NIF radical in a time-dependent manner when it interacted with human umbilical vein endothelial cells (HUVECs). The electron paramagnetic resonance (EPR) signal of NO-NIF radicals in HUVECs showed an asymmetric pattern suggesting that the radicals were located in the membrane. The NO-NIF radicals had radical scavenging activity for 1,1-diphenyl-2-picrylhydrazyl, whereas neither NO-NIF nor nifedipine did. In addition, the NO-NIF radical more effectively quenched lipid peroxides than NO-NIF or nifedipine. Furthermore, NO-NIF attenuated the superoxide-derived free radicals in HUVECs stimulated with LY83583, and suppressed iron-nitrilotriacetic acid (Fe-NTA)-induced cytotoxicity in rat pheochromocytoma (PC12) cells. Our findings suggest that NO-NIF is a candidate for a new class of antioxidative drugs that protect cells against oxidative stress.
Chemical & pharmaceutical bulletin 01/2011; 59(2):208-14. · 1.70 Impact Factor
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ChemInform 01/2010; 31(25).
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ABSTRACT: Highly substituted chromans have been constructed in a highly stereoselective manner by a palladium-catalyzed reaction of propargylic carbonates with 2-(2-hydroxyphenyl)acetates. Enantioselective reactions also successfully proceeded to give the optically active chromans with high enantioselectivity.
Organic Letters 10/2009; 11(20):4752-5. · 5.86 Impact Factor
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ABSTRACT: The N-Heterocyclic carbene-catalysed oxidative carboxylation of arylaldehydes with water successfully proceeded when a sulfoxylalkyl-substituted imidazolium salt was used as the catalyst. The reactions can be run in the absence of oxidant, and a variety of arylaldehydes having an electron-withdrawing group were converted to the corresponding carboxylic acids.
Organic & Biomolecular Chemistry 10/2009; 7(19):4062-6. · 3.70 Impact Factor
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ABSTRACT: The enantioselective total syntheses of enokipodins A and B, alpha-cuparenone-type sesquiterpenoids with antimicrobial activity, have been achieved. The key step is the enantiospecific construction of the quaternary carbon center using a palladium-catalyzed addition of an arylboronic acid to an allene followed by an Eschenmoser-Claisen rearrangement.
Organic Letters 03/2009; 11(6):1441-3. · 5.86 Impact Factor
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Synthesis-stuttgart. 01/2009; 2009(17):2893-2904.
