研究者詳細 - 坂倉　彰

論文 - 坂倉　彰

分割表示 103 件中 61 - 80 件目／全件表示 >>

Enantioselective biomimetic polyene cyclization of polyprenoids - Long-sought enantioselective reaction induced by a "chiral halonium ion" 査読

Akira Sakakura, Kazuaki Ishihara

CHIMICA OGGI-CHEMISTRY TODAY 25 ( 5 ) 9 - 12 2007年9月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：TEKNOSCIENZE PUBL

Enantioselective biomimetic polyene cyclizations of polyprenoids have been studied for a long time. Very recently, we have developed the first "chiral iodonium ion"-induced enantioselective polyene cyclization of polyprenoids using a nucleophilic promoter. Achiral nucleophilic phosphorus compounds catalytically promote the diastereoselective halocyclization in dichloromethane to give a halogenated cyclic product in excellent yield. Moreover, chiral phosphoramidites stoichiometrically promote the enantioselective halocyclization of simple polyprenoids with N-iodosuccinimide in toluene to give iodinated cyclic products in up to 99 percent ee and 99 percent ds. Some enantioselective polycyclizations have been reported in addition to this halocyclization. One of the advantages of these biomimetic polycyclizations is the simultaneous formation of several carbon-carbon bonds with the relative and absolute stereocontrol. Enantioselective biomimetic domino reactions would be highly useful for the practical synthesis of natural products and related compounds.

Catalytic synthesis of peptide-derived thiazolines and oxazolines using Bis(quinolinolato)dioxomolybdenum(VI) complexes 査読

Akira Sakakura, Rei Kondo, Shuhei Umemura, Kazuaki Ishihara

ADVANCED SYNTHESIS & CATALYSIS 349 ( 10 ) 1641 - 1646 2007年7月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY-V C H VERLAG GMBH

Bis(2-ethyl-8-quinolinolato)dioxomolybdenum(VI) (9) (1 mol%) shows remarkable catalytic activity for the dehydrative cyclization of cysteine-containing dipeptides 1 to give the corresponding thiazolines 2 with less than 6% epimerization at the C2-exomethine position. For the dehydrative cyclization of threonine-containing dipeptides 4, 1 mol% of bis(2-phenyl-8-quinolinolato)dioxomolybdenum(VI) (10) gives the corresponding oxazolines 5 with retention of configuration at the 5-position.

DOI： 10.1002/adsc.200700068

Dehydrative cyclization catalyzed by the combination of molybdenum(VI) oxides and benzoic acids: First synthesis of the antitumour substance BE-70016 査読

Akira Sakakura, Shuhei Umemura, Rei Kondo, Kazuaki Ishihara

ADVANCED SYNTHESIS & CATALYSIS 349 ( 4-5 ) 551 - 555 2007年3月

担当区分：筆頭著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY-V C H VERLAG GMBH

The dehydrative cyclization of N-(o-hydroxybenzoyl)threonine derivative la is efficiently promoted by the combined use of molybdenum(VI) oxides and benzoic acids bearing electron-withdrawing substituents. In the presence of ammonium molybdate [(NH4)(2)MoO4, 10 mol %] and pentafluorobenzoic acid (C6F5CO2H; 10 mol %), dehydrative cyclization of la was conducted in toluene under azeotropic reflux conditions to give 2-(o-hydroxyphenyl)oxazoline 2a in 76 % yield. Furthermore, the first total synthesis of the antitumour substance BE-70016 was achieved using the catalytic dehydrative cyclization of la as a key reaction.

DOI： 10.1002/adsc.200600550

Design of highly functional small-molecule catalysts and related reactions based on acid-base combination chemistry 査読

Kazuaki Ishihara, Akira Sakakura, Manabu Hatano

SYNLETT ( 5 ) 686 - 703 2007年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：GEORG THIEME VERLAG KG

The design of small but highly functional artificial catalysts is very important for practical organic synthesis. We have succeeded in the rational design of small and simple catalysts and related reactions based on acid-base combination chemistry. Acid-base combined catalysts can be classified into three types: (i) acid-base combined salt catalysts, (ii) conjugate acid-base catalysts, and (iii) nonconjugate acid-base catalysts. We have systematically developed acid-base combined salt catalysts such as ammonium salts, ate complexes, ion pairs and cation-pi complexes, acid-base conjugate catalysts such as metal oxides (monoconjugation) and zinc(Il)3,3'-diphosphinol-BINOLates (triconjugation), and acid-base nonconjugate catalysts like L-histidine-derived sulfonamides.

DOI： 10.1055/s-2007-970776

Enantioselective halocyclization of polyprenoids induced by nucleophilic phosphoramidites 査読

Akira Sakakura, Atsushi Ukai, Kazuaki Ishihara

NATURE 445 ( 7130 ) 900 - 903 2007年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：NATURE PUBLISHING GROUP

Polycyclic bio-active natural products that contain halogen atoms have been isolated from a number of different marine organisms(1). The biosynthesis of these natural products appears to be initiated by an electrophilic halogenation reaction at a carbon - carbon double bond(2-4) via a mechanism that is similar to a proton-induced olefin polycyclization(5-8). Enzymes such as haloperoxidases generate an electrophilic halonium ion ( or its equivalent), which reacts with the terminal carbon - carbon double bond of the polyprenoid, enantioselectively inducing a cyclization reaction that produces a halogenated polycyclic terpenoid. Use of an enantioselective halocyclization reaction is one possible way to chemically synthesize these halogenated cyclic terpenoids; although several brominated cyclic terpenoids have been synthesized via a diastereoselective halocyclization reaction that uses stoichiometric quantities of a brominating reagent(9-12), the enantioselective halocyclization of isoprenoids induced by a chiral promoter has not yet been reported. Here we report the enantioselective halocyclization of simple polyprenoids using a nucleophilic promoter. Achiral nucleophilic phosphorus compounds are able to promote the diastereoselective halocyclization reaction to give a halogenated cyclic product in excellent yields. Moreover, chiral phosphoramidites promote the enantioselective halocyclization of simple polyprenoids with N-iodosuccinimide to give iodinated cyclic products in up to 99% enantiomeric excess and diastereomeric excess. To the best of our knowledge, this is the first successful example of the enantioselective halopolycyclization of polyprenoids.

DOI： 10.1038/nature05553

Unusual rate acceleration in bronsted acid catalyzed dehydration reactions: Local hydrophobic environment in aggregated N-(2,6-diphenylphenyl)-N-mesitylammonium pentafluorobenzenesulfonates 査読

Akira Sakakura, Hitoshi Watanabe, Shoko Nakagawa, Kazuaki Ishihara

CHEMISTRY-AN ASIAN JOURNAL 2 ( 4 ) 477 - 483 2007年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY-V C H VERLAG GMBH

Bulky diarylammonium pentafluorobenzenesulfonates effectively promote dehydration reactions, such as condensation reactions to give esters and the dehydrative cyclization of 1,3.5-triketones. In particular, N-(2,6-diphenylphenyl)-N-mesitylammonium pentafluorobenzenesulfonate shows much higher catalytic activity than C6F5SO3H under reaction conditions without the removal of generated water, even though the former is a weaker acid. Its crystallization gives an aggregated cyclic ion pair, which is composed of two diarylammonium cations, four pentafluorobenzenesulfonate anions, and two oxonium cations. This ion pair is strongly stabilized by four intermolecular and two intramolecular pi-pi attractive interactions and 10 hydrogen bonds. The extremely high catalytic activity of N-(2,6-diphenylphenyl)-N-mesitylammonium pentafluorobenzenesulfonate in the dehydration reactions may be ascribed to the local hydrophobic environment of the tightly aggregated ammonium salts.

DOI： 10.1002/asia.200600380

Direct ester condensation catalyzed by bulky diarylammonium pentafluorobenzenesulfonates 査読

Akira Sakakura, Shoko Nakagawa, Kazuaki Ishihara

NATURE PROTOCOLS 2 ( 7 ) 1746 - 1751 2007年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：NATURE PUBLISHING GROUP

A protocol for ester condensation between equimolar amounts of carboxylic acids and alcohols catalyzed by bulky diarylammonium pentafluorobenzenesulfonate is described. We also present procedures for the synthesis of N-(2,6-diisopropylphenyl)-N-mesitylammonium pentafluorobenzenesulfonate. The present ester condensation proceeds well under mild conditions even without the removal of generated water. The synthesis of N-(2,6-diisopropylphenyl)-N-mesitylammonium pentafluorobenzenesulfonate will take similar to 5 days. The ester condensation reactions will take similar to 6 h to 3 days.

DOI： 10.1038/nprot.2007.254

Bulky phosphazenium cation catalysis for dehydrative condensation of phosphoric acid with alcohols 査読

Akira Sakakura, Mikimoto Katsukawa, Takaomi Hayashi, Kazuaki Ishihara

GREEN CHEMISTRY 9 ( 11 ) 1166 - 1169 2007年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ROYAL SOC CHEMISTRY

A metal-free phosphazenium cation-catalyzed direct dehydrative condensation of phosphoric acid with alcohols has been developed for the environmentally benign synthesis of phosphoric acid monoesters.

DOI： 10.1039/b707974e

The oxorhenium(VII)-catalyzed direct condensation of phosphoric acid with an alcohol 査読

Akira Sakakura, Mikimoto Katsukawa, Kazuaki Ishihara

ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 46 ( 9 ) 1423 - 1426 2007年

Enantioselective Diels-Alder reaction of alpha-acyloxyacroleins catalyzed by chiral 1,1 '-binaphthyl-2,2 '-diammonium salts 査読

Akira Sakakura, Kenji Suzuki, Kazuaki Ishihara

ADVANCED SYNTHESIS & CATALYSIS 348 ( 16-17 ) 2457 - 2465 2006年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WILEY-V C H VERLAG GMBH

A diammonium salt of chiral 1,1'-binaphthyl-2,2'-diamine (2a) and trifluoromethanesulfonimide (Tf2NH) shows excellent catalytic activity and enantioselectivity for the Diels-Alder reaction of alpha-acyl-oxyacroleins. For example, in the presence of 5 mol % of 2a and 9.5 mol % of Tf2NH, the Diels-Alder reaction of alpha-(cyclohexanecarbonyloxy)acrolein with cyclopentadiene proceeded in EtCN at -75 degrees C to give the adducts in 88 % yield with 92 % exo and 91 % ee. The electron-donating property of the acyl group of the alpha-acyloxyacroleins increases the enantioselectivity due to the formation of strong intramolecular hydrogen bonding of the acyl group with a proton of the ammonium group in the transition state. This catalyst can be easily prepared in situ by mixing the commercially available chiral diamine and Tf2NH.

DOI： 10.1002/adsc.200600322

35 細胞毒性マクロリド配糖体、オーリサイド類の合成(口頭発表の部)

末永聖武, 星野紘史, 好井孝典, 森和規, 曽根大紀, 別所祐紀, 坂倉彰, 早川一郎, 山田靜之, 木越英夫

天然有機化合物討論会講演要旨集 ( 48 ) 205 - 210 2006年9月

記述言語：日本語出版者・発行元：天然有機化合物討論会

Aurisides A (1) and B (2) are macrolide glycosides isolated from Japanese sea hare Dolabella auricuralia, which exhibit cytotoxicity against HeLa S_3 cells with IC_<50> values of 0.17 and 1.2μg/mL, respectively. The main structural features of aurisides are a bromine-substituted conjugated diene, a 14-membered lactone, and a cyclic hemiacetal. We achieved the enantioselective synthesis of aurisides A and B by a convergent approach. The C1-C9 segment 4 was prepared from (R)-pantolactone using a reaction of dithiane carbanion with epoxide, stereoselective reduction of β-hydroxyketone with Me_4NBHOAc, and rhodium-catalyzed Reformatsky-type reaction as key steps. The C10-C17 segment 12 was synthesized from (R)-glycidyl trityl ether. The Nozaki-Hiyama-Kishi reaction between 4 and 12 and subsequent reactions including construction of bromine-substituted conjugated diene gave seco acid 10, which was converted into the aglycon (3) of aurisides by construction of the 14-membered lactone. The Mukaiyama glycosylation reaction of the aglycon 3 provided aurisides A (1) and B (2).

DOI： 10.24496/tennenyuki.48.0_205

8 海洋産抗腫瘍性化合物アプリロニンAの抗腫瘍機序(口頭発表の部)

黒田武史, 末永聖武, 半田知久, 宮沙織, 岡本和人, 兼松憲吾, 坂倉彰, 山田靜之, 平田邦生, 高田昌樹, 加藤健一, 村岡真, 山本雅貴, 田中宏志, 木越英夫

天然有機化合物討論会講演要旨集 ( 48 ) 43 - 48 2006年9月

記述言語：日本語出版者・発行元：天然有機化合物討論会

The interaction between actin and aplyronine A, a potent antitumor and actin-depolymerizing substance of marine origin, was investigated by photoaffinity labeling experiments and X-ray structure analysis of actin complex with aplyronine A. Photoaffinity probes consisting of a side-chain portion of aplyronine A as a ligand, a diazirine moiety as a photoaffinity group, and a fluorophor as a detecting group were synthesized. Photolabeling experiments between actin and the probe were carried out. Actin was successfully photolabeled by the fluorescent probe and visualized clearly. The present results provide the first chemical evidence for the direct interaction between actin and the side-chain portion of aplyronine A. X-ray structure analysis of actin-aplyronine A complex was carried out. The analysis showed that Aplyronine A bound to a hydrophobic cleft between subdomains 1 and 3 of actin. The structural feature is that the trimethylserine moiety protrudes toward the bulk solvent region.

DOI： 10.24496/tennenyuki.48.0_43

Enantioselective synthesis of aurisides A and B, cytotoxic macrolide glycosides of marine origin 査読

Kiyotake Suenaga, Hiroshi Hoshino, Takanori Yoshii, Kazunori Mori, Hiroki Sone, Yuhki Bessho, Akira Sakakura, Ichiro Hayakawa, Kiyoyuki Yamada, Hideo Kigoshi

TETRAHEDRON 62 ( 33 ) 7687 - 7698 2006年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD

The enantioselective synthesis of aurisides A and B, macrolide glycosides of marine origin, was achieved by a convergent approach. The C1-C9 segment 4 was prepared from (R)-pantolactone, and the C10-C17 segment 14 was synthesized from (R)-glycidyl trityl ether. The Nozaki-Hiyama-Kishi reaction between 4 and 14 and subsequent reactions gave seco acid 10, which was converted into the aglycon (3) of aurisides by construction of the 14-membered lactone and bromine-substituted conjugated diene. The glycosylation reaction of the aglycon provided aurisides A and B. (c) 2006 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tet.2006.05.077

Synthesis and biological activity of mycalolide analogs 査読

Kiyotake Suenaga, Tomoyuki Kimura, Takeshi Kuroda, Keita Matsui, Saori Miya, Satomi Kuribayashi, Akira Sakakura, Hideo Kigoshi

TETRAHEDRON 62 ( 35 ) 8278 - 8290 2006年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD

Mycalolide analog 4, consisting only of the side chain of mycalolide B (2), a trisoxazole macrolide of marine origin, was stereoselectively synthesized using Roush crotylboration, an Evans aldol reaction, and a Paterson aldol reaction as key steps. The analog 4 was found to have strong actin-depolymerizing activity. (c) 2006 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tet.2006.06.046

P-81 ENANTIOSELECTIVE POLYENE HALOCYCLIZATION INDUCED BY NUCLEOPHILIC CHIRAL PHOSPHINES

Sakakura Akira, Ukai Atsushi, Ishihara Kazuaki

International Symposium on the Chemistry of Natural Products 2006 "P - 81" 2006年7月

Development of environmentally benign catalytic dehydration process 査読

Akira Sakakura, Kazuaki Ishihara

JOURNAL OF SYNTHETIC ORGANIC CHEMISTRY JAPAN 64 ( 6 ) 651 - 663 2006年6月

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：SOC SYNTHETIC ORGANIC CHEM JPN

More environmentally benign alternatives to current chemical processes, especially large-scale fundamental reactions, are highly desirable for many reactions. We have developed bulky diary-lammonium pentafluorobenzenesulfonates la and 2a as mild and extremely active dehydration catalysts. In the presence of the catalysts, dehydrative cyclization of 1, 3, 5-triketones and ester condensation of carboxylic acids with equimolar amounts of alcohols are performed in heptane by heating at 80 V without the removal of water. We have also developed an efficient molybdenum oxide-catalyzed dehydrative cyclization of serine, threonine, and cysteine derivatives, which gives oxazolines and thiazolies. In the presence of molybdenum oxides, the reaction is carried out by heating at azeotropic reflux with the removal of water. Phosphate monoesters are synthesized from a mixture of phosphoric acid and alcohols in the presence of tributylamine. The reaction is promoted by nucleophilic bases such as N-butylimidazole. The hydroxyl groups of amino alcohols, such as 5'-hydroxyl group of 2, 3'-O-isopropylidene ribonucleosides, are phosphorylated selectively.

DOI： 10.5059/yukigoseikyokaishi.64.651

Chiral 1,1 '-binaphthyl-2,2 '-diammonium salt catalysts for the enantioselective Diels-Alder reaction with alpha-acyloxyacroleins 査読

Akira Sakakura, Kenji Suzuki, Kazuhiko Nakano, Kazuaki Ishihara

ORGANIC LETTERS 8 ( 11 ) 2229 - 2232 2006年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER CHEMICAL SOC

A diammonium salt of chiral 1,1'-binaphthyl-2,2'-diamine and trifluoromethanesulfonimide (Tf2NH) shows excellent catalytic activity and enantioselectivity for the Diels-Alder reaction of alpha-acyloxyacroleins with cyclic dienes. For example, in the presence of 5 mol % of the ammonium catalyst, the Diels-Alder reaction of alpha-(cyclohexanecarbonyloxy) acrolein with cyclopentadiene proceeded in EtCN at -75 degrees C to give the adducts in 88% yield with 92% exo and 91% ee. This catalyst can be easily prepared in situ by mixing the commercially available chiral diamine and Tf2NH.

DOI： 10.1021/ol060490l

Study of the interaction between actin and antitumor substance aplyronine A with a novel fluorescent photoaffinity probe 査読

Takeshi Kuroda, Kiyotake Suenaga, Akira Sakakura, Tomohisa Handa, Kazuhito Okamoto, Hideo Kigoshi

Bioconjugate Chemistry 17 ( 2 ) 524 - 529 2006年3月

記述言語：英語掲載種別：研究論文（学術雑誌）

The interaction between actin and aplyronine A, a potent antitumor and actin-depolymerizing substance of marine origin, was investigated by photoaffinity labeling experiments. Photoaffinity probes consisting of a side-chain portion of aplyronine A as a ligand, a diazirine moiety as a photoaffinity group, and a fluorophore as a detecting group were synthesized. Photolabeling experiments between actin and the probe were carried out. Actin was successfully photolabeled by the fluorescent probe and visualized clearly. The present results provide the first chemical evidence for the direct interaction between actin and the side-chain portion of aplyronine A. © 2006 American Chemical Society.

DOI： 10.1021/bc050324i

Bulky diarylammonium arenesulfonates as mild and extremely active dehydrative ester condensation catalysts 査読

Akira Sakakura, Shoko Nakagawa, Kazuaki Ishihara

Tetrahedron 62 ( 2-3 ) 422 - 433 2006年1月

記述言語：英語掲載種別：研究論文（学術雑誌）

More environmentally benign alternatives to current chemical processes, especially large-scale, fundamental reactions like ester condensations, are highly desirable for many reactions. Bulky diarylammonium pentafluorobenzenesulfonates and tosylates serve as extremely active dehydration catalysts for the ester condensation reaction of carboxylic acids with equimolar amounts of sterically demanding alcohols and acid-sensitive alcohols. Typically, the esterification reaction is performed in heptane by heating at 80°C in the presence of 1 mol% of the catalyst without removing water. Esterification with primary alcohols proceeds without solvents even at room temperature. Furthermore, 4-(N-mesitylamino)polystyrene resin-bound pentafluorobenzenesulfonate can be recycled more than 10 times without a loss of activity. © 2005 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.tet.2005.09.059

P-12 酸化モリブデン触媒を用いる脱水環化反応によるオキサゾリン、チアゾリンの効率的合成(ポスター発表の部)

坂倉彰, 近藤玲, 梅村周平, 石原一彰

天然有機化合物討論会講演要旨集 ( 47 ) 475 - 480 2005年9月

記述言語：日本語出版者・発行元：天然有機化合物討論会

Oxazoline, oxazole, thiazoline, and thiazole rings are important constituents of numerous bioactive natural products and pharmaceuticals. The biosynthesis of many naturally occurring oxazolines and thiazolines appears to involve the dehydrative cyclization of serine, threonine, and cysteine residues. Oxazoles and thiazoles are synthesized by the oxidation of oxazolines and thiazolines, respectively. We describe here a biomimetic synthesis of oxazolines and thiazolines catalyzed by molybdenum (IV or VI) oxides, their mode of cyclization is retentive at the β-position. In the course of screening various metal oxides as catalysts for the dehydrative cyclization of dipeptides 1a and 1b, we found that molybdenum oxides had good catalytic activities. Interestingly, the ammonium salts of molybdenum(VI) oxides, (NH_4)_6Mo_7O_<24>・4H_2O and (NH_4)_2MoO_4, exhibited remarkable catalytic activities and gave oxazolines 2a and 2b in a short reaction time, along with small amounts of 3a and 3b. Next, we examined the dehydrative cyclization of cysteine derivatives 4a and 4b to thiazolines 5a and 5b using molybdenum oxides as catalysts. In the case of the dehydrative cyclization of 4a, (NH_4)_6Mo_7O_<24>・4H_2O, (NH_4)_2MoO_4 and MoO_2(acac)_2 showed excellent catalytic activities. MoO_2(acac)_2 could catalyze the dehydrative cyclization of 4b, to give 5b in 70% yield along with 5c (15%). To the best of our knowledge, this is the first example of the catalytic dehydrative cyclization of dipeptide substrates that include serine, threonine, and cysteine residues. A key synthetic intermediate 11 of hennoxazole A and bis(oxazoline)s 13a and 13b were synthesized by the dehydrative cyclization using molybdenum oxide catalysts. In addition, polyaniline-supported MoO_2(acac)_2 could easily be recovered and reused.

DOI： 10.24496/tennenyuki.47.0_475

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