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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: 20th July, 2018

Paper | Regular issue | Prepress
DOI: 10.3987/COM-18-13918
Cinchona Alkaloid Thiourea-Catalyzed One-Pot Synthesis and Bioselective Activities of β-Amino Acid Ester Derivatives Containing a Pyrimidine Moiety

Song Bai,* Shan Liu, Yunying Zhu, Xian Wei, Kunhong Zhao, Weihua Li, and Qin Wu*

*School of Chemical Engineering, Guizhou Institute of Technology, 1st, Caiguan Road, Yunyan District, Guiyang City, Guizhou Province 550003, China

Abstract

We have studied the synthesis of enantiomerically pure optically active β-amino acid ester derivatives with good biological activities. Here, we report that both enantiomers of β-amino acid ester derivatives that contain a pyrimidine moiety can be produced in an enantioselective Mannich-type one-pot reaction with good yields and excellent enantiomeric excess (up to >99% ee) by chiral cinchona alkaloid thiourea catalysts. An evaluation of the antiviral activities of our reaction products against tobacco mosaic virus (TMV) was promising with high and selective biological activities. Compound ()-4h showed an excellent anti-TMV activity (curative activity, 56.1%; inactivation activity, 70.7%; protection activity, 95.7%) at 500 μg/mL. These values exceed those of the commercially available antiviral agent, ningnanmycin (curative activity, 52.6%; inactivation activity, 62.0%; protection activity, 90.2%). These novel chiral compounds could be used as protective agents against TMV disease.

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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: 6th July, 2018

Paper | Regular issue | Prepress
DOI: 10.3987/COM-18-13922
5,11-Diethyl-6-formylindolo[3,2-b]carbazole: Crystal, Interaction with Protein and Theoretial Study

Yingchun Gu, Dayong Lin, Xuening Fei,* Lei Zhang, Cuihong Wang, Qi Yang, Shiyang Liu, Xueling Ren, and Ran Zhang

*School of Science, Tianjin Chengjian University, No.26 Jinjing Road, Xiqing District 300384, China

Abstract

In this work, 5, 11-diethyl-6-formylindolo[3,2-b]carbazole (DEFICZ) was crystallized in a monoclinic crystal system with the space group of P121/n1. Its spectral properties and potential interaction with protein including BSA and HSA were also studied correspondingly. The crystal structure was theoretically investigated using the density functional tight-binding method. In order to address the regioselective associated with the synthesis of DEFICZ, the B3LYP density functional theory (DFT) calculation has been carried out to estimate the relative stability of different active intermediates. In addition, time-dependent density functional theory method was used to unveil the origin of the absorption spectra of DEFICZ as observed experimenta.

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Published online: 6th July, 2018

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-18-13926
A Facile Synthesis of Indolo[2,3-b]Carbazoles from the Reaction of Di(2-Indolyl)Methane and Aromatic Aldehydes Catalyzed by Oxalic Acid

Chun Li, Xunhua Lu, Yuanyong Yang, and Lin Zhang*

*Department of Pharmacy, Guizhou Medical University, No. 9, Beijing Road, Guiyang, 550014, China

Abstract

Oxalic acid catalyzed condensation of di(2-indolyl)methane with aromatic aldehydes has been established. Various indolo[2,3-b]carbazole derivatives were prepared in good isolated yields (up to 94.5%). Compared with literature methods, the present protocol features mild reaction conditions, easily controlled selectivity, good functional group tolerance, and simple operation procedures.

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Published online: 6th July, 2018

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-18-13938
A New Short Synthesis of (±)-Olean Through Cross Metathesis

Nektarios S. Kranidiotis, Constantinos E. Grammatoglou, and John K. Gallos*

*Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece

Abstract

A new synthesis of (±)-1,7-dioxaspiro[5.5]undecane (olean), the olive fruit fly pheromone, utilizing the cross-metathesis reaction as the key-step, is reported.

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Published online: 6th July, 2018

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-18-13939
An Efficient Construction of 9-(Guaiazulen-1-Yl)-Xanthen-4-(9H)-ones via Domino Reaction

Yu Liu, Jiao Xu,* Dao-Lin Wang,* Wei Ma, and Xing-Wei Zhang

*College of Chemistry and Chemical Engineering, Bohai University, 19, Keji Rd., New Songshan District, Jinzhou City, Liaoning Province 121001, China

Abstract

A facile, convenient, and efficient synthesis of 9-(guaiazulen-1-yl)-xanthen-4-(9H)-one derivatives has been developed by the condensation of guaiazulene with salicylaldehyde, and 1,3-hexanediones in the presence of L-proline as the catalyst via the tandem Knoevenagel–Michael reaction.

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Published online: 4th July, 2018

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-18-13933
A Facile Synthesis of 4-Aryl-1H-2-benzothiopyran-3-carboxylic Acid Derivatives from o-Bromobenzyl Mercaptans

Kazuhiro Kobayashi,* Syunta Furugaki, and Takuma Ueyama

*Applied Chemistry Field, Chemistry and Biotechnology Course, Department of Engineering, Graduate School of Sustainability Science, Tottori University, 4-101 Koyama-minami, Tottori 680-8552, Japan

Abstract

The synthesis of 4-aryl-1H-2-benzothiopyran-3-carboxylic acid derivatives by a sodium hydride-mediated thiopyran ring formation of 2-[(2- aroylphenyl)methylsulfanyl]acetic acid derivatives is reported. The precursors were prepared by successive treatment of lithium o-lithiobenzyl mercaptides, which were generated by the reaction of o-bromobenzyl mercaptans with two equivalents of butyllithium, with aromatic aldehydes and 2-bromoacetonitrile or tert-butyl 2-bromoacetate, followed by oxidation of the resulting sulfanyl alcohols with pyridinium chlorochromate (PCC).

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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

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-18-13913
Water Assisted and Choline Chloride-Dimethylurea Deep Eutectic Salts as Catalyst towards the Attractive Reaction of Indole, Benzaldehyde, and Malononitrile

Hongli Ruan, Yue Lv, Shijun Yu, Chengwei Lv,* and Yue An*

*School of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian 116029, China

Abstract

The condensation of indole, benzaldehyde, and malononitrile was relatively rigorous compared with other Yonemitsu type reaction. We described a strategy using catalytic amount of choline chloride-dimethylurea deep eutectic salts as cheap and safe accelerator. We also found that introducing right amount of water in reaction system was crucial. This method tolerates variations in all three components to get desired 3-substituted indoles in satisfactory yields.

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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: 28th June, 2018

Paper | Regular issue | Prepress
DOI: 10.3987/COM-18-13920
Construction of PQQ-Enzyme Multi-Immobilized Electrodes for Electrocatalytic Reduction of Carbonyl Compounds

Yoshitomo Kashiwagi,* Tetsuya Ono, Kentaro Yoshida, Toshinori Ito, and Nobuki Sakurai*

*School of Pharmaceutical Sciences, Ohu University, 31-1 Misumido, Tomita-machi, Koriyama, Fukushima 963-8611, Japan

Abstract

A thin poly(arylamine) (PAA) and poly(acrylic acid) (PAAc) layers-coated graphite felt (GF) electrode immobilizing all mediation components of pyrroloquinolinequinone (PQQ), diaphorase (Dp), oxidized nicotinamide adenine dinucleotide (NAD+) and alcohol dehydrogenase (ADH) to construct a complete bioelectrochemical reactor was prepared and applied to electrocatalytic reduction of carbonyl compounds in a phosphate buffer at constant potential of –0.65 V vs. Ag/AgCl. The carbonyl compounds were reduced to the corresponding alcohols with high current efficiency (97.2 – 100%) and high yield (97.4 – 100%), respectively.

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Published online: 28th June, 2018

Paper | Regular issue | Prepress
DOI: 10.3987/COM-18-13934
Silver-Mediated 2-Arylation/Alkylation/Acylation of Benzothiazoles with Aldehydes in Water

Min Hua, Chunqin Wang, Qixing Liu,* Danyi Chen, Hao Fu, and Haifeng Zhou*

*Research Center of Green Pharmaceutical Technology and Process, Hubei Key Laboratory of Natural Products Research and Development, College of Biological and Pharmaceutical Sciences, China Three Gorges University, Yichang 443002, China

Abstract

An efficient and environmentally benign method was developed for the facile synthesis of various 2-aryl and 2-alkyl substituted benzothiazoles in moderate to good yields, using a silver-mediated redox condensation of benzothiazoles and aldehydes in water. Furthermore, this method is also applicable to prepare 2-acyl benzothiazoles.

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Published online: 26th June, 2018

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-18-13911
Synthesis of 5-Hydroxythieno[2,3-d]pyrimidin-6(5H)-one Derivatives by the Reaction of 2-(4-Chloropyrimidin-5-yl)-2-hydroxyalkanoate with Sodium Hydrogensulfide

Kazuhiro Kobayashi,* Ikuma Murayama, Ryoga Ono, Daiki Fujiwara, Hidetaka Hiyoshi, and Kazuto Umezu

*Applied Chemistry Field, Chemistry and Biotechnology Course, Department of Engineering, Graduate School of Sustainability Science, Tottori University, 4-101 Koyama-minami, Tottori 680-8552, Japan

Abstract

A convenient sequence for the preparation of 5-hydroxythieno[2,3-d]pyrimidin-6(5H)-one derivatives from 4,6-dichloro-2-(methylsulfanyl)pyrimidine (DCSMP) has been developed. Thus, 4,6-dichloro-5-lithio-2-(methylsulfanyl)pyrimidine, generated by the reaction of DCSMP with lithium diisopropylamide (LDA), was allowed to react with α-keto esters to afford 2-(4,6-dichloropyrimidin-5-yl)-2-hydroxyalkanoate derivatives. These underwent cyclization on treatment with sodium hydrogensulfide to give the corresponding 4-chloro-5-hydroxythieno[2,3-d]pyrimidin-6(5H)-one derivatives. After displacement of one of the two chloro groups of 2-(4,6-dichloropyrimidin-5-yl)-2-hydroxyalkanoate derivatives with methoxy, dialkylamino, or ethyl(or phenyl)sulfanyl groups, the resulting 2-(4-chloropyrimidin-5-yl)-2-hydroxyalkanoates were similarly treated with sodium hydrogensulfide to afford the corresponding desired products.

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Published online: 26th June, 2018

Paper | Regular issue | Prepress
DOI: 10.3987/COM-18-13916
Deprotonation of 4-Ethynylpyrazolium Salts

Nils Lennart Ahlburg, Olivia Doppleb, Kai Hillrichs, Jan C. Namyslo, Eike G. Hübner, and Andreas Schmidt*

*Clausthal University of Technology, Institute of Organic Chemistry, Leibnizstrasse 6, D-38678 Clausthal-Zellerfeld, Germany

Abstract

4-Ethynyl-1,2-dimethylpyrazolium salts were prepared by methylation of the corresponding 4-ethynyl-1-methylpyrazoles with trimethyloxonium tetrafluoroborate and were deprotonated to give the corresponding pyrazolium-4-acetylenides, which are mesomeric betaines. These can be represented as alkynyl- or mesoionic allenylidene-type resonance forms. Calculations and spectroscopic investigations were performed to determine the contribution of each canonical form to the overall structure. Ylides and N-heterocyclic carbenes are tautomers of the betaines. Their relative stabilities have been compared.

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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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Published online: 25th June, 2018

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-18-13931
Synthesis and DNA Cleavage Activity of Novel Spiro Pyrazol-3-ones Containing Isoxazoline Moiety

Eiichi Masumoto, Emi Shirouzu, 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

An approach to the synthesis of novel spiro pyrazol-3-ones containing isoxazoline moiety is described. A plausible mechanism for the conversion is proposed. The spiro compounds were formed via potassium carbonate-assisted intramolecular cyclocondensation reaction of β-hydroxy ketoximes, which were prepared from pyrazol-3-ones containing β-hydroxy ketone moiety through an oximation. On the other hand, treatment of the β-hydroxy ketoximes with [hydroxy(tosyloxy)iodo]benzene (HTIB) caused an oxidative N–O coupling reaction to give the spiro pyrazol-3-ones containing isoxazoline N-oxide moiety. All the synthesized compounds were characterized by spectroscopic analysis and were tested for their DNA cleavage activity.

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Published online: 22nd June, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(T)95
Asymmetric Synthesis of β-Lactams by Intramolecular Conjugate Addition of Serine and Cysteine Derivatives via Memory of Chirality

Ryuichi Hyakutake, Tomoyuki Yoshimura, Yoshihiro Ueda, Kazuhiro Hayashi, Takumi Furuta, and Takeo Kawabata*

*Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan

Abstract

The 4-exo-trig cyclization of axially chiral enolates generated from L-serine and L-cysteine dervatives proceeded predominately over β-elimination to give chiral β-lactams with contiguous tri- and tetrasubstituted carbon centers in up to 96% ee. The key to smooth production of β-lactams is the use of Cs2CO3 and CF3CH2OH as a base and a proton source, respectively. A strongly electron-withdrawing Michael acceptor in the substrates was also critical for high enantioselectivity of the β-lactam formation.

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Published online: 22nd June, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(T)94
2-Functionalized Derivatives of 2-Bromo-1,3-dimethylimidazole

Martin Lampl, Gerhard Laus, Klaus Wurst, Volker Kahlenberg, Thomas Gelbrich, Sven Nerdinger,* Hubert Huppertz, and Herwig Schottenberger

*Sandoz GmbH, Biochemiestrasse 10, 6250 Kundl, Austria

Abstract

Attempts of direct bromination of 1,3-dimethylimidazolium salts with bromine were futile. A tribromide or a carbene–lithium–THF adduct were received instead. The quaternary 2-bromo compound was obtained by methylation of 2‑bromo‑1‑methylimidazole and subsequent ion metathesis, which was converted to the corresponding 2-cyano and 2-azido derivatives. Typical reactions of the latter include a dipolar cycloaddition and the Staudinger reaction. Crystal structures of eight compounds have been determined by single-crystal X-ray diffraction.

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Published online: 22nd June, 2018

Communication | Regular issue | Prepress
DOI: 10.3987/COM-18-13927
Synthesis of an Anlog of Amphidinol 3 Corresponding to the C31–C67 Section

Tomoyuki Koge, Yuma Wakamiya, Makoto Ebine, and Tohru Oishi*

*Department of Chemistry, Faculty and Graduate School of Science, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan

Abstract

An artificial analog corresponding to the C31–C67 section of amphidinol 3 (AM3) was designed as a part of the structure–activity relationship studies to elucidate structure requirements for eliciting antifungal activity. To reduce the number of synthetic steps, the 43-deoxy-51-epi derivative containing common tetrahydropyran ring system was designed and synthesized from a pivotal intermediate in 17 steps. The analog elicited no antifungal activity, suggesting that not only the two tetrahydropyran rings, but also polyol section of AM3 are necessary to elicit antifungal activity.

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Published online: 20th June, 2018

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(T)87
A Synthetic and Spectroscopic Investigation of the Asymmetric α-Lithiation-trapping of Six-Membered N-Boc Heterocycles using Alexakis Diamines

James D. Firth, Giacomo Gelardi, Peter J. Rayner, Darren Stead, and Peter O'Brien*

*Department of Chemistry, University of York, Heslington, York YO10 5DD, U.K.

Abstract

The asymmetric lithiation-trapping of six-membered N-Boc heterocycles using s-BuLi and two different Alexakis diamines is reported. These readily available ligands outperform the current ‘best-in-class’ sparteine-type diamines in the lithiation and benzophenone trapping of N-Boc piperazines and the lithiation-cyclisation-trapping of N-Boc-4-chloropiperidine. In situ IR spectroscopy has been used to optimise lithiation times and to discover previously unknown subtleties regarding the lithiation step.

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Published online: 20th June, 2018

Review | Special issue | Prepress
DOI: 10.3987/REV-18-SR(T)3
β-Amino Alcohol Organocatalysts for Asymmetric Cycloadditions

Hiroto Nakano,* Isiaka Alade Owolabi, Madhu Chennapuram, Yuko Okuyama, Eunsang Kwon, Chigusa Seki, Michio Tokiwa, and Mitsuhiro Takeshita

*Division of Sustainable and Environmental Engineering, Graduate School of Engineering, Muroran Institute of Technology, 27-1 Mizumoto, Muroran, Hokkaido 050-8585, Japan

Abstract

A design of a chiral organocatalyst is very important for obtaining of a chiral product with a high optical purity in a catalytic asymmetric reaction. Recently, we developed a series of chiral β-amino alcohol organocatalysts A that showed high level of catalytic activity in some asymmetric reactions. These β-amino alcohols are stable in air, and have two advantageous features, easy preparation and exhibiting high stereoselectivity in an enantioselective reaction. This review summarizes our recent works involving the Diels-Alder (DA) reactions of 1,2-dihydropyridines, anthrones or 3-hydroxy-2-pyridones as dienes with dienophiles, the asymmetric 1,3-dipolar cycloaddition of nitrones with α,β-unsaturated aldehydes and the crossed aldol reaction of isatins with acetaldehyde, by the use of the simple primary β-amino alcohols as efficient chiral organocatalysts for the asymmetric reactions.

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Published online: 19th June, 2018

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-18-13910
Synthesis of Bicyclo[2.2.2]octadiene-Fused Sapphyrins and Their Thermal Conversion

Tetsuo Okujima,* Toshiki Abe, Shigeki Mori, Takahiro Nakae, and Hidemitsu Uno

*Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577, Japan

Abstract

A series of sapphyrins fused with bicyclo[2.2.2]octadiene were successfully synthesized via [3+1+1] porphyrinoid synthesis. The retro DielsAlder thermal conversion afforded the corresponding di-, tri-, tetra-, and pentabenzosapphyrins.

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Published online: 14th June, 2018

Review | Regular issue | Prepress
DOI: 10.3987/REV-18-885
Developments toward the Production of Diverse Natural-Product-Like Compounds: Diversity-Oriented Synthesis and Diversity-Enhanced Extracts

Haruhisa Kikuchi* and Yoshiteru Oshima*

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

Abstract

Natural products and their derivatives have proven very useful in the search for biologically active compounds and in the development of new drugs because of their structural diversity. However, new approaches that may increase the chemical diversity of such natural products must be developed in order to retain the future usefulness of these compounds. Diversity-oriented synthesis (DOS) has recently emerged as an efficient methodology for constructing complex and diverse compounds from simple and similar precursors. Through the combination of natural product chemistry and DOS, we therefore propose a new approach, diversity-enhanced extracts, for increasing the diversity of natural-product-like compounds. This review describes recent developments toward the production of diverse natural-product-like compounds by DOS based on natural products and direct chemical derivatization of natural extracts, including diversity-enhanced extracts.

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Published online: 14th June, 2018

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)4
Efficient Synthesis of Methyl (S)-4-(1-Methylpyrrolidin-2-yl)-3-oxobutanoate as the Key Intermediate for Tropane Alkaloid Biosynthesis with Optically Active Form

Nanda Kumar Katakam, Cole W. Seifert, John D’Auria,* and Guigen Li*

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

Abstract

Methyl (S)-4-(1-methylpyrrolidin-2-yl)-3-oxobutanoate has been synthesized for enzymatic studies on cyclization enzymes during cocaine biosynthesis in Erythroxylum coca plants. During the present new synthesis, L-proline was first protected with Cbz group and reduced to chiral amino alcohol, which were then followed by Swern oxidation, Wittig reaction and decarboxylative condensation. At the last step, N-methylamino acid precursor was treated with 1,1’-carbonyldiimidazole followed by reacting with methyl potassium malonate to give the 3-oxobutanoate in 54% overall yield. This new strategy has proven to avoid obvious racemization of the L-proline chiral center during the synthesis. In addition, six of the eight synthesis steps were performed via GAP chemistry/technology without the use of column chromatography for purification.

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Published online: 13th June, 2018

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-18-13923
Synthesis of (E)-N-Substituted 1,2-Benzothiazol-3(2H)-imine 1,1-Dioxide Derivatives from Secondary Benzenesulfonamides and Isothiocyanates

Kazuhiro Kobayashi* and Daiki Fujiwara

*Applied Chemistry Field, Chemistry and Biotechnology Course, Department of Engineering, Graduate School of Sustainability Science, Tottori University, 4-101 Koyama-minami, Tottori 680-8552, Japan

Abstract

A new and simple method for the preparation of (E)-N-substituted 1,2-benzothiazol-3(2H)-imine 1,1-dioxide derivatives has been developed. 2,N-Dilithiobenzenesulfonamides, generated by the treatment of secondary benzenesulfonamides with two equivalents of butyllithium, react with isothiocyanates to afford the corresponding 2-(aminosulfonyl)benzothioamides, which undergo ring closure with a formal elimination of hydrogen sulfide on treatment with thionyl chloride in the presence of two equivalents of pyridine to provide the desired products. Acid hydrolysis of some of these products leads to the formation of N-substituted saccharins.

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Published online: 12th June, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(T)91
Preparation of meso-Silylporphyrins via Nickel-Catalyzed Coupling of meso-Brominated Ni(II) Porphyrins with Silylzinc Reagents

Satoshi Hayashi,* Taiga Endo, and Toshikatsu Takanami*

*Pharmaceutical Sciences, Meiji Pharmaceutical University, 2-522-1 Noshio, Kiyose, Tokyo 204-8588, Japan

Abstract

In this paper, we developed a technique for the nickel-catalyzed coupling of meso-brominated Ni(II) porphyrins with silylzinc reagents in order to prepare meso-silyl-substituted Ni(II) porphyrins. Porphyrin silylation occurs under mild conditions and exhibits both excellent substrate generality and functional group compatibility.

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Published online: 12th June, 2018

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(T)75
Synthesis Of N- [4-(2'-[18f]Fluoroalkoxybenzoyl)]- And N-(3-[123i]Iodo-4-Methoxybenzoyl)Pyrrolidin-2-Ones As Potential Brain Imaging Agents

Murthy R. Akula, David Blevins, George W. Kabalka,* and Dustin Osborne

*Department of Chemistry, University of Tennessee, Knoxville, Tennessee, 37996-1600, U.S.A.

Abstract

The microfluidic synthesis of promising brain imaging PET agents N-[4-(2’-[18F]fluoroalkyloxybenzoyl)]pyrrolidin-2-ones 13a-c was accomplished by nucleophilic radiofluorination of the corresponding tosylate precursors 9a-c with kryptofix-potassium carbonate-[18F]fluoride. Decay corrected radiochemical yields of 35±5% (13a), 38±8% (13b) and 40±5% (13c) were obtained with radiochemical purities of ≥ 93%. The total reaction time, including HPLC purification was 40 min. N-(3-[123I]Iodo-4- methoxybenzoyl)pyrrolidin-2-one, 18, was prepared by radioiododestannylation of tin precursor 17 using Na123I and 0.3% peracetic acid in 84% radiochemical yield in 20 min.

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