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Published online: 19th October, 2018

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)37
Selective Aromatic Nucleophilic Substitution of 4-(Dimethylamino)-2-methoxy-3-(trifluoroacetyl)quinoline with Thiols – DFT Calculation Study

Norio Ota, Yusuke Harada, Yasuhiro Kamitori, and Etsuji Okada*

*Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan

Abstract

The nucleophilic aromatic substitution proceeds exclusively at the 4-position of 4-(dimethylamino)-2-methoxy-3-(trifluoroacetyl)quinoline 1 by the reaction with various thiols to give the corresponding N-S exchanged products solely, and no O-S exchange reactions at the 2-position are performed. Our DFT calculation study provides a rational explanation regarding this complete selectivity based on energies of the adducts 6, 7 which are corresponding to the O-protonated Meisenheimer complexes at carbonyl oxygen in 3-trifluoroacetyl group. It was also investigated about influences of the solvents on the present unique selective substitution with thiols referring the results for the analogous selective substitution on 1 using amines as a nucleophile.

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Published online: 19th October, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)24
Four-Component Coupling Strategy for 2,3,4-Trisubstituted 3,4-Dihydroquinoline

Hiroki Yamagishi, Shun Tsuchiya, Hayate Saito, Keisuke Nogi, Jun Shimokawa, and Hideki Yorimitsu*

*Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan

Abstract

Trimethylsilyllithium attacked selectively at the 4-position of 2-(methylsulfanyl)quinoline. The lithium enamide intermediate generated in situ reacted with a series of electrophiles to introduce a substituent at the 3-position of the dihydroquinoline skeleton. Combined with the conversion of the 2-methylsulfanyl group to an aryl group via palladium-catalyzed Negishi-type coupling reaction, the net four-component coupling transformation in two steps provided a 2,3,4-trisubstituted 3,4-dihydroquinoline skeleton.

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Published online: 19th October, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)28
Arylboronic Acid-Mediated Glycosylation of 1,2-Dihydroxyglucoses

Sanae Izumi, Yusuke Kobayashi, and Yoshiji Takemoto*

*Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29 Yoshida-shimoadachi-machi, Sakyo-ku, Kyoto 606-8501, Japan

Abstract

We explored direct dehydrative coupling of tetrahydro-2H-pyran-2,3-diol or a 1,2-dihydroxy sugar with various alcohols using a range of arylboronic acids. Among the catalysts, 2-borono-4-trifluoromethylbenzoic acid efficiently promoted acetalization of tetrahydro-2H-pyran-2,3-diol. Ferroceniumboronic acid showed the best catalytic activity for glycosylation of the 1,2-dihydroxy sugar. The major products were 1,2-cis-α-D-glucopyranosides.

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Published online: 19th October, 2018

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)34
Synthesis and DNA Cleavage Activity of Novel Spiro[cyclobutathiazole-4,4’-pyrazole] Derivatives

Eiichi Masumoto, Hayate Nagabuchi, Nobuhiro Kashige, Fumi Okabe-Nakahara, Fumio Miake, Kenji Yamagata, and Hiroshi Maruoka*

*Faculty of Pharmaceutical Sciences, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan

Abstract

A facile and efficient synthesis of novel spiro pyrazole derivatives containing cyclobutathiazole moiety is described. The key substrate pyrazole-thiazolidine derivative as the building block for bis-heterocycles was formed via a Knoevenagel-type condensation of thiazolidinedione with pyrazol-3-one. Thermal treatment of the pyrazole-thiazolidine derivative with orthoesters in refluxing toluene caused an C-attack nucleophilic substitution, followed by an intramolecular cyclization/elimination sequence, giving the corresponding spiro[cyclobutathiazole-4,4’-pyrazole] derivatives. All the synthesized compounds were characterized by spectroscopic analysis and were tested for their DNA cleavage activity in vitro.

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Published online: 18th October, 2018

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)31
Studies toward the Synthesis of Perforatumone: Synthesis of the 7-Oxabicyclo[4.2.1]nonane-8,9-dione Core

Tatsuki Nakajima, Keita Takiguchi, Keisuke Yoshida, Akihiro Ogura, and Ken-ichi Takao*

*Department of Applied Chemistry, Keio University, Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan

Abstract

Construction of the unique bridged bicyclic skeleton, 7-oxabicyclo[4.2.1]nonane-8,9-dione, of perforatumone was achieved. Key steps included a Dieckmann-type condensation, a Claisen rearrangement, and an intramolecular Michael reaction.

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Published online: 17th October, 2018

Review | Special issue | Prepress
DOI: 10.3987/REV-18-SR(F)2
Chemistry of Nitroaziridines

Feiyue Hao and Nagatoshi Nishiwaki*

*School of Environmental Science and Engineering, Kochi University of Technology, Tosayamada-cho, Kami, Kochi, 782-8502, Japan

Abstract

This review article introduced synthetic procedures for the preparation of structurally diverse nitroaziridines. In addition, this article also summarized reactivity of nitroaziridines caused by the inherent strain and high electrophilicity of the small ring. These properties facilitate their use as a functionalized building blocks in synthetic and medicinal chemistry.

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Published online: 17th October, 2018

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)44
Concise Synthesis of Anticancer Active trans-4-(4-Octylphenyl)prolinol

Junki Ando, Aoi Tazawa, Kohei Ishizawa, Minoru Tanaka,* and Hiroyoshi Takamura*

*Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan

Abstract

Concise synthesis of anticancer active trans-4-(4-octylphenyl)prolinol has been achieved. Regioselective iodination of aromatic compound and subsequent Suzuki–Miyaura cross-coupling with trans-1-octen-1-ylboronic acid produced the desired coupling product. Further transformation of this product afforded trans-4-(4-octylphenyl)prolinol. The synthesis of this anticancer compound has been performed with 23% overall yield and six steps, which have been improved in comparison with those (3.5% overall yield and eight steps) previously reported.

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Published online: 16th October, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)36
Concise Synthesis of Kalasinamide, Marcanine A, and Geovanine, and Antiproliferative Activity Evaluation of Their Azaanthracenones

Takashi Nishiyama, Noriyuki Hatae,* Kyohko Chikaraishi, Keisuke Uchida, Chika Yokoyama, Satoshi Hibino, and Tominari Choshi*

*Graduate School of Pharmacy & Pharmaceutical Sciences, Fukuyama University, Fukuyama, Hiroshima 729-0292, Japan

Abstract

The total syntheses of kalasinamide (1), marcanine A (2), and geovanine (3) have been conducted by the formation of a fused pyridone-ring azaanthracenone core based on a Curtius rearrangement that is followed by the microwave-assisted thermal electrocyclization of an isocyanato-containing 2-azahexatriene system. The antiproliferative activities of these synthetic compounds against the HCT-116 colon tumor cells were evaluated by the MTT assay.

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Published online: 16th October, 2018

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)39
Nucleophilic Addition to N-benzoylisoquinolinium Cation Catalyzed by Sodium Tetracyanocyclopentadienides

Takeo Sakai,* Mai Hattori, Akari Tada, Junpei Matsuoka, and Yuji Mori

*Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya 468-8503, Japan

Abstract

Tetracyanocyclopentadienide-catalyzed nucleophilic addition to an N-benzoylisoquinolinium cation is reported. The reaction is accelerated by the in situ formation of the soluble lipophilic salt of an N-benzoylisoquinolinium cation and a tetracyanocyclopentadienide anion.

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Published online: 15th October, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)38
Design and Synthesis of Cyclohexenyl-p-carborane Derivatives as a New Class of Progesterone Receptor Antagonists

Shinya Fujii, Naoki Yanagida, Shuichi Mori, Emiko Kawachi, and Hiroyuki Kagechika*

* Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-0062, Japan

Abstract

We report here the synthesis and structure-activity relationships of a series of C-cyclohexenyl-p-carborane derivatives, which we designed as candidates for a novel class of progesterone receptor (PR) antagonists. Biological evaluation using T47D alkaline phosphatase assay revealed that several compounds exhibited potent PR-antagonistic activity. We also examined the selectivity of these compounds for PR over androgen receptor (AR). Among them, 11b functioned as a PR-selective antagonist, while other compounds, such as 13b, acted as PR/AR dual antagonists. Notably, docking simulations indicated that 11b and 13b bind in similar orientations to the ligand-binding site of PR, but in opposite orientations to that of AR. These findings could helpful for developing more selective ligands for PR.

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Published online: 12th October, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)23
Computational Studies on the Racemization Barriers of Winding Vine-Shaped Heterobiaryls with Molecular Asymmetry

Atsunori Mori,* Shiomi Ashida, Yukiko Ito, Jiaqiang Cheng, Toyoko Suzuki, Kentaro Okano, and Takayoshi Hashimoto

*Department of Chemical Science and Engineering, Kobe University, Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan

Abstract

DFT calculation studies were performed for the estimation of racemization barrier of winding vine-shaped heterobiaryls showing molecular asymmetry. The calculated value showed good agreement compared with that derived from experimental studies. Effects of hetroaromatic structure, carbon-carbon double bond at the winding-vine moiety, substituent at the double bond, and substituent at the heteroaromatic rings were studied.

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Published online: 2nd October, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)27
Heterosubstituted 4-Vinylimidazoles – Preparation and Diels-Alder Reactions

Abhisek Ray, Sabuj Mukherjee, Jayanta Das, Manoj Bhandari, Apsara Herath, Muhammed Yousufuddin, and Carl J. Lovely*

*Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, Texas 76019-0065, USA.

Abstract

The Diels-Alder reactions of vinylimidazole derivatives provide an expedient stereocontrolled entry into polysubstituted tetrahydrobenzimidazole derivatives. Prior studies from our group have described methods for postcycloaddition functionalization of these adducts, however, in several cases we have been unable to achieve appropriate elaboration of cycloadducts and have sought alternatives. To circumvent this problem we have investigated pre-cycloaddition functionalization through the preparation of vinyl-substituted derivatives. Initial studies with vinyl halides or silyl enol ethers were compromised either by poor yields or postcycloaddition elimination. However, vinylsilanes and vinylstannanes participate in Diels-Alder reactions with retention of the heterosubstituent and provide a means for further elaboration, for example through Fleming-Tamao oxidation.

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Published online: 19th September, 2018

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)25
Formal Synthesis of Gephyrotoxin 287C

Katsuki Takashima and Naoki Toyooka*

*Graduate School of Innovative Life Science, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan

Abstract

The enantioselective formal synthesis of (-)-gephyrotoxin 287C (1) has been achieved from octahydroquinolinone 8. The α, β-unsaturated ester 16, whose enantiomer was a key intermediate for the total synthesis of (+)-1, was synthesized by highly stereoselective Michael-type conjugate addition reaction to 8 and subsequent transformations.

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Published online: 14th September, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)30
Biomimetic Synthesis of Iheyamine A from Spirocyclic Oxindoles

Takumi Abe,* Syuhei Satake, and Koji Yamada*

*Faculty of Pharmaceutical Sciences, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido 061-0293, Japan

Abstract

The biomimetic synthesis of azepinobisindole alkaloid iheyamine A from a spirocyclic oxindole via an oxidative rearrangement has been accomplished for the first time. Furthermore, an unprecedented method for constructing 2,1’-spirocyclic oxindoles from azepinobisindoles through an alternative oxidative rearrangement has been explored.

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Published online: 14th September, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)29
Synthesis of γ-Difluoromethylated Tetronate Derivatives from Squarates Using Difluoromethylphosphonate

Yoshihiko Yamamoto,* Yuki Ishida, Takashi Kurohara, Masatoshi Shibuya, and Takeshi Yasui

*Department of Basic Medicinal Sciences, Graduate School of Pharmaceutical Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan

Abstract

A new method for the synthesis of γ-difluoromethylated tetronates was developed using diethyl difluoromethylphosphonate as a difluoromethyl (CF2H) surrogate. The addition of a lithiated difluoromethylphosphonate to (semi)squarates at –90 °C afforded 4-hydroxycyclobutenones, which were converted into the corresponding tetronates by oxidative ring expansion using Pb(OAc)4. The final dephosphorylation was performed in MeOH using Cs2CO3 as the base, affording the desired γ-difluoromethyltetronates.

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Published online: 3rd September, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)26
Synthetic Studies on Plakinidines

Takahito Satoh, Touma Adachi, Kentaro Okano, Juri Sakata, and Hidetoshi Tokuyama*

*Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, 980-8578, Japan

Abstract

Synthetic studies on plakinidines are described. As a model study for the construction of the dihydropyridone ring at the final stage of the synthesis, we investigated a Meyer–Schuster rearrangement/aza-Michael cyclization cascade. The B,C,D,E ring system possessing a pyrrolo[2,3,4-kl]acridine structure was constructed via a benzyne-mediated cyclization/functionalization sequence that involved the formation of a β,β-diarylethylamine derivative and a palladium-catalyzed double aryl amination of a 3-arylindoline intermediate as key processes.

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Published online: 3rd September, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)22
Palladium-Catalyzed Arylation of N-Aminoimidazol-2-ones towards Synthesis of Constrained Phenylalanine Dipeptide Mimics

Julien Poupart, Ngoc-Duc Doan, Damien Bérubé, Yousra Hamdane, Caleb Medena, and William D. Lubell*

*Département de chimie, Université de Montréal, C.P. 6128, Succursale Centre-Ville, Montréal, Québec H3C3J7, Canada.

Abstract

N-Aminoimidazol-2-ones (e.g., 6) offer potential to serve as constrained amino amide components that can induce turn conformation in peptide sequences. To add side chain functionality onto this amino amide surrogate, mild conditions have now been developed for palladium-catalyzed arylation of N-aminoimidazol-2-ones. A diverse array of aryl iodides reacted at the 5-position of N-aminoimidazol-2-one dipeptides 7 and 10 in a general approach for making constrained arylalanine dipeptide turn mimics (e.g., 8 and 11).

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Published online: 29th August, 2018

Communication | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)21
An Efficient Silver Tetrafluoroborate-Catalyzed Cycloisomerization of Ynamides

Winai Ieawsuwan* and Somsak Ruchirawat

*Chulabhorn Research Institute, Laboratory of Medicinal Chemistry, 54 Kamphaeng Phet 6 Road, Laksi, Bangkok 10210, Thailand

Abstract

A silver catalyzed-cycloisomerization of N-Boc protected ynamides has been developed under mild reaction conditions to provide a wide range of oxazol-2(3H)-ones in good to excellent yields. Moreover, the acid-promoted Pictet-Spengler cyclization of oxazol-2(3H)-ones was described to furnish the corresponding trans-oxazolidones in moderate yields.

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Published online: 13th August, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)18
Indium Mediated Allylation of N-tert-butanesulfinyl Imines with 1,3-Dibromopropene: Stereoselective Synthesis of Aziridines

Edgar Maciá, Francisco Foubelo,* and Miguel Yus*

*Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Alicante, Apdo. 99 03080 Alicante, Spain

Abstract

The reaction of N-tert-butanesulfinyl imines 1 with 1,3-dibromopropene (2), in the presence of indium metal, in saturated aqueous solution of sodium bromide, produced bromohomoallylamine derivatives 3 with total facial diastereoselectivity for the imine addition, and moderate yields. These compounds were easily transformed into the corresponding vinyl aziridines 5 upon deprotonation with KHMDS in THF, the intramolecular cyclization taking place in a stereospecific manner in moderate to high yields.

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Published online: 13th August, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)20
Diastereoselective Synthesis of Poly-Substituted SYN-Imidazolidine-2-thiones via Microwave-assisted Three-Component [2+2+1] Heterocyclizations

Jie-Yu Hu, Yi-Yun Gao, Wen-Wen Zhang, Ke-Ying Zhang, Wen-Lian Li, Wen-Juan Hao,* Bo Jiang, and Guigen Li*

*Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061, U.S.A.

Abstract

An efficient and simple three-component reaction of arylglyoxals, isothiocyanates and arylamines has been developed, delivering poly-substituted syn-imidazolidine-2-thione derivatives with high diastereo- and regioselectivity (up to > 99:1). The microwave-assisted transformation is easy to perform simply by mixing readily available starting materials, thereby featuring mild reaction conditions, bond-forming efficiency and atom-economy.

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Published online: 9th August, 2018

Communication | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)19
Diastereoselective Synthesis of 5-Iodoalkenyl-2-oxazolines by Electrophilic Cyclization of Allenyl Amides

Tsukasa Hirokane, Ayaka Kawakami, Kenji Matsumoto, and Masahiro Yoshida*

*Faculty of Pharmaceutical Sciences, Tokushima Bunri University, 180 Nishihamabouji, Yamashiro-cho, Tokushima, 770-8514, Japan

Abstract

The electrophilic cyclization of allenyl amides is described. Allenyl amides were easily prepared from the propargyl aziridines via the [1,5]-hydrogen shift followed by the conversion of the imine moiety to the amides. 5-Iodoalkenyl-2-oxazolines having a variety of substituents were diastereoselectively obtained by the reaction of the allenyl amides with iodine.

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Published online: 6th August, 2018

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)17
Site-Selective Synthesis of Acacetin and Genkwanin through Lipase-catalyzed Deacetylation of Apigenin 5,7-Diacetate and Subsequent Methylation

Rie Fujita, Susanta Mandal, Kengo Hanaya, Mitsuru Shoji, Shuhei Higashibayashi, and Takeshi Sugai*

*Department of Pharmaceutical Sciences, Faculty of Pharmacy, Keio University, 1-5-30 Shiba-Kouen, Minato-ku, Tokyo, Japan

Abstract

Candida antarctica lipase B-catalyzed deacetylation proceeded with high site-selectivity on the C-4’ acetyl group in apigenin triacetate to give apigenin 5,7-diacetate. Methylation of the liberated hydroxy group with the combination of trimethyloxonium tetrafluoroborate (Meerwein reagent) and 1,8-bis(dimethylamino)naphthalene (proton sponge) in CH2Cl2 proceeded in a quantitative manner to give the product methylated at the C-4’ hydroxy group (acacetin 5,7-diacetate). Even with the same precursor, a different methylation product at the C-7 hydroxy group (genkwanin 4’,5-diacetate) was obtained in 86% yield by applying iodomethane and Cs2CO3 in dimethyl sulfoxide (DMSO). The methylated products were deprotected to form acacetin and genkwanin. We inferred that the latter unexpected methylation was ascribable to the intermolecular migration of an acetyl group from C-7 to C-4’. DFT calculations indicated that the C-7 phenoxide ion was 12.6 kJ/mol more stable than the initially formed C-4’ phenoxide ion.

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Published online: 23rd July, 2018

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)12
Lipase-Catalyzed Site-Selective Deacetylation of Sterically Hindered Naphthohydroquinone Diacetate and Its Application to the Synthesis of a Heterocyclic Natural Product

Riichi Hashimoto, Ayaka Sakakura, Kengo Hanaya, Shuhei Higashibayashi, and Takeshi Sugai*

*Department of Pharmaceutical Sciences, Faculty of Pharmacy, Keio University, 1-5-30 Shiba-Kouen, Minato-ku, Tokyo, Japan

Abstract

Lipase-catalyzed site-selective deacetylation of 2,5-dimethylnaphthalene-1,4-diol diacetate was examined. With Candida antarctica lipase B, the suppressing effect of a methyl substituent at the peri-position of the α-naphthyl ester over that at the ortho-position was significant. This site-selectivity was in contrast to that of chemical hydrolysis reported to date. From the resulting monoacetate, mansonone F, a physiologically active heterocyclic orthoquinone, was synthesized in 38% yield in as few as three steps.

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Published online: 20th July, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)16
Structure–Activity Relationship Study of Gatastatin Based on the Topliss Tree Approach

Ichiro Hayakawa,* Shuya Shioda, Takumi Chinen, Takeo Usui, and Hideo Kigoshi*

*Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan

Abstract

Various analogues of gatastatin, a γ-tubulin-specific inhibitor, were designed and synthesized by systematically optimizing the aromatic ring at the O7-benzyl group in accordance with an operational Topliss tree, and their biological activities were evaluated. Some derivatives showed stronger cytotoxicity against HeLa cells than gatastatin. Especially, the cytotoxicity of the meta-chloro derivative was about 18-fold stronger than that of gatastatin. However, these derivatives did not exhibit binding ability to the yeast γ-tubulin small complex or inhibitory activity against α,β-tubulin polymerization. These results suggested that γ-tubulin strongly recognized the unsubstituted phenyl ring of the O7-benzyl group in gatastatin.

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Published online: 12th July, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)11
New Indole Alkaloids from Ervatamia cumingiana

Mariko Kitajima, Shumpei Nakano, Noriyuki Kogure, Sanan Subhadhirasakul, and Hiromitsu Takayama*

*Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8675, Japan

Abstract

Two new Iboga-vobasine-type bisindole alkaloids N-demethylervahanine A (1) and N-demethylervahanine B (2) and one new chippiine-type alkaloid 3-O-methyl-10,11-demethoxychippiine (3) were isolated from the roots of Ervatamia cumingiana collected in Thailand. Their chemical structures were determined by spectroscopic analyses. Compounds 1 and 2 are bisindole alkaloids having a linkage between C-3 in the vobasine unit and C-11' or C-10' in the Iboga unit, respectively.

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Published online: 11th July, 2018

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)13
C-Glycosidation of Unprotected Aldopentoses with Ketones Using Proline-Triethylamine as Catalyst

Jithender Enukonda, Sherida Johnson, and Fujie Tanaka*

*Chemistry and Chemical Bioengineering Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna, Okinawa 904-0495, Japan

Abstract

Reactions of unprotected aldopentoses with ketones catalyzed by proline and triethylamine that afford C-glycoside derivatives are described.

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Published online: 6th July, 2018

Communication | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)2
Synthesis of Orthogonally Protected Actinoidic Acid Trimethyl Ether

Yusuke Amino* and Robert M. Williams*

*Department of Chemistry, Colorado State University, 301 West Pitkin Street, 80523, U.S.A.

Abstract

We describe the asymmetric synthesis of actinoidic acid trimethyl ether with orthogonal protecting groups on the respective amino and carboxyl groups. The Stille biaryl coupling reaction of suitably functionalized aryl bromide and (trimethylstannyl)benzaldehyde gave the key intermediate biaryl aldehyde. Synthesis was accomplished by applying the asymmetric Strecker reaction to this aldehyde, followed by selectively removing the chiral auxiliary. By comparing its 1H-NMR spectra with those obtained from vancomycin, the stereochemistry of the synthesized diastereoisomer of actinoidic acid trimethyl ether was confirmed as an atropisomer of the (αS,αR)-isomer.

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Published online: 2nd July, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)9
Efficient Synthesis of O-Linked Glycoconjugates of Amino Acids from Carbohydrate-Derived Donor-Acceptor-Cyclopropanes

Gade Kishore, Vibha Gautam, Shrutisagar Dattatraya Haveli, and Srinivasan Chandrasekaran*

*Department of Organic Chemistry, Indian Institute of Science, Bangalore-560 012, India

Abstract

N-Iodosuccinimide (NIS) mediated ring opening of carbohydrate-derived donor-acceptor-cyclopropanes with free “CO2H” group of N-protected L-amino acids at ambient conditions afforded iodo derivatives of glycosyl ester of L-amino acids. The iodides were subsequently converted easily into corresponding azides using NaN3 in DMF followed by reduction with Zn/AcOH to produce ester linked glycosyl amino acids. A similar strategy was adopted to synthesize C-linked glycoamino acid derivatives from different N-protected L-amino alcohols. By using an orthogonal strategy C- and O-linked glycopeptides were also synthesized.

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Published online: 28th June, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)5
Csf-Promoted Desilylation and Ring-Contraction Reaction of Electron-Deficient 3-Silyl-2H-Chromenes to 2-Benzylbenzofurans

Kenta Tanaka, Mayumi Sukekawa, Mami Kishimoto, Yujiro Hoshino, and Kiyoshi Honda*

*Graduate School of Environment and Infomation Science, Yokohama National University, Tokiwadai 156, Hodogaya-ku, Yokohama 240-8501, Japan

Abstract

The ring-contraction reaction of electron-deficient 3-silyl-2H-chromenes to 2-benzylbenzofurans under mild conditions was developed. CsF efficiently promoted the reaction at room temperature or 80 ºC to afford a variety of 2-benzylbenzofurans in good yields. 3-Silyl-2H-chromenes having strong electron-withdrawing groups smoothly afforded the desired products. The reaction is proposed to proceed through an allenyl intermediate or dyotropic rearrangement.

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Published online: 25th June, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)8
Stereodivergent and Stereoselective Synthesis of cis- and trans-4-Substituted Prolinols

Junki Ando, Aoi Tazawa, Kohei Ishizawa, Minoru Tanaka,* and Hiroyoshi Takamura*

*Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan

Abstract

Stereoselective synthesis of 4-substituted prolinol derivatives has been developed. Thus, Suzuki–Miyaura cross-coupling of vinyl triflate provided the common synthetic intermediates toward the stereodivergent synthesis of cis- and trans-4-substituted prolinols. These two kinds of target compounds were obtained by diastereoselective hydrogenation of the coupling products with Pd/C and Crabtree catalyst, respectively. In addition, the obtained 4-substituted prolinol was transformed to the corresponding proline derivative via oxidation in one step.

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