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Regular & Special Issues

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Published online: 25th March, 2019

Review | Regular issue | Prepress
DOI: 10.3987/REV-19-902
Synthesis, Stereochemical Stability, and Biological Activity of Stemonamine and Its Related Stemona Alkaloids

Takayuki Iwata and Mitsuru Shindo*

*Institute for Materials Chemistry and Engineering, Kyushu University, Kasuga-koen, Kasuga 816-8580, Japan

Abstract

More than 140 Stemona alkaloids have been isolated from Stemona plants (of the Stemonaceae species). These alkaloids represent a unique pyrrolo[1,2-a]azepine nucleus, and can be classified into eight groups on the basis of their chemical aspects. This study is focused on the synthesis of stemonamine group alkaloids, in addition to their chemical stability and biological activity.

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Published online: 22nd March, 2019

Paper | Regular issue | Prepress
DOI: 10.3987/COM-19-14048
One-Pot Cascade Synthesis of Pyrazole Based Isosteres of Valdecoxib by a [3+2] Cycloaddition Sequence and Evaluation of Their Cox Inhibitory Activity

Silvia Roscales,* Nicole Bechmann, Jens Pietzsch, and Torsten Kniess*

*Department of Radiopharmaceutical and Chemical Biology, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, 01328 Dresden, Germany

Abstract

A series of 5-methyl-3,4-diaryl-substituted 1H-pyrazoles, N-isosteres of valdecoxib, was synthesized by a [3+2] cycloaddition/[1,5] sigmatropic rearrangement sequence starting from tosylhydrazine, aryl methyl ketones and terminal aryl alkynes bearing various substituents (H, Me, OMe, F, SO2Me, SO2NH2). New pyrazoles were prepared regioselectively in a one-pot process with moderate-good yields. All compounds were used in in vitro cyclooxygenase (COX) assays to determine inhibitory potency and selectivity to COX-1 and COX-2. In general, these new pyrazoles are characterized by selective COX-2 inhibition activity in a micromolar range.

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Published online: 18th March, 2019

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-19-14034
Three New Arylbenzofuran Lignans from Arctium lappa and Their Anti-Tobacco Mosaic Virus Activity

Wan-Li Zeng, Meng-Jie Liang, Shan-Shan Hu, Qian Gao, Chun-Man Song, Hai-Tao Huang, Yong Xu, Hai-Ying Xiang, Liang Deng, Guang-Yu Yang, Yin-Ke Li, Ya-Dong Guo,* and Qi-Li Mi*

*Key Laboratory of Tobacco Chemistry of Yunnan Province, China Tobacco Yunnan Industrial Co., Ltd, 650231, Kunming, China

Abstract

Three new (1-3), together with two known (4 and 5) arylbenzofuran lignans were isolated from the seed of Arctium lappa. Their structures were elucidated by spectroscopic methods, including extensive 1D- and 2D-NMR techniques. Compounds 1-3 were evaluated for their anti-tobacco mosaic virus (Anti-TMV) activity. The results showed that compounds 1-3 showed potential anti-TMV activities with inhibition rates of 33.5%, 32.8%, and 34.2%, at the concentration of 20 µM, respectively. These rates are higher than that of positive control.

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Published online: 18th March, 2019

Paper | Regular issue | Prepress
DOI: 10.3987/COM-19-14042
Palladium/Benzimidazolium Salt Catalyst Systems and N-Heterocyclic Carbene-Palladium(II)-Pyridine (PEPPSI) Complexes for Anti-Markovnikov Hydroaminations of Styrene in Ionic Liquid

Yetkin Gök, Beyhan Yiğit, Özlem Özeroğlu Çelikal, and Murat Yiğit*

*Department of Chemistry, Faculty of Science and Art, Adıyaman University, 02040 Adıyaman, Turkey

Abstract

Both in situ prepared Pd-NHC and NHC-Pd-PEPPSI complexes were tested as catalysts in the intermolecular hydroamination reactions between styrene with various anilines in ionic liquid. All of the compounds tested here are catalytically active for the intermolecular hydroamination of styrene with aromatic amines. The anti-Markovnikov addition products were obtained selectively by using 1 mol% of the palladium complex.

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Published online: 15th March, 2019

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-19-14055
Synthesis of [1,4]Oxathiino[2,3-d]pyrimidines Starting with 4,6-Dichloro-2-(methylsulfanyl)pyrimidine

Kazuhiro Kobayashi,* Kota Yamasaki, 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 method for the preparation of 7-(het)aryl[1,4]oxathiino[2,3-d]pyrimidine derivatives using an easily operated two-step sequence starting from 4,6-dichloro-2-(methylsulfanyl)pyrimidine (DCSMP) have been developed. Thus, the starting material is treated with LDA to generate the 5-lithio derivative, which is allowed to react with sulfur and then phenacyl bromide and its derivatives to give 1-(het)aryl-2-{[4,6-dichloro-2-(methylsulfanyl)pyrimidin-5-yl]sulfanyl}ethanones. These pyrimidinyl ketones undergo ring closure upon treatment with triethylamine to provide the corresponding desired products in reasonable overall yields from DCSMP.

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Published online: 14th March, 2019

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-18-14026
Synthesis and Optical Studies of 2,4,5-Tri[2-(aryl)ethenyl]-1H-imidazoles

Rabia Babar and Munawar Ali Munawar*

*Institute of Chemistry, University of the Punjab, Lahore 54590, Pakistan

Abstract

A series of Y-shaped 2,4,5-tri(arylethenyl)-1H-imidazoles (2a-2c) has been synthesized. The synthesized compounds have been characterized by IR, NMR, Mass and elemental analyses. The optical properties were investigated by using absorption and emission measurements. The compound 2b, containing nitro group has been found non-fluorescent. The absorption and emission properties have helped us to find the effect of substituent on the optical properties.

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Published online: 14th March, 2019

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-19-14054
Agesamines A and B, New Dibromopyrrole Alkaloids from the Sponge Agelas sp.

Ayako Katsuki, Hikaru Kato, Yuji Ise, Fitje Losung, Remy E. P. Mangindaan, and Sachiko Tsukamoto*

*Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-hon-machi, Kumamoto 862-0973, Japan

Abstract

New dibromopyrrole alkaloids, agesamines A (1) and B (2), were obtained as an inseparable epimeric mixture from a marine sponge Agelas sp., collected in Indonesia. The planar structures were elucidated by analysis of spectroscopic data, and the absolute configuration was determined by the calculated ECD spectrum.

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Published online: 13th March, 2019

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-19-14041
Three New Anti-Tobacco Mosaic Virus Prenyl Chromone Derivatives from Cassia nomame

Yong Xu, Qi-Li Mi, Yin-Ke Li, Wan-Li Zeng, Qian Gao, Chun-Man Song, Hai-Tao Huang, Hai-Ying Xiang, Xue-Mei Li, Guang-Yu Yang, Qiu-Fen Hu,* and Jin Wang*

*Key Laboratory of Chemistry in Ethnic Medicinal Resources, Yunnan Minzu University, Kunming 650031, China

Abstract

Three new (1-3), together with four known (4-7) prenyl chromone derivatives were isolated from the whole plants of Cassia nomame. Their structures were elucidated by spectroscopic methods, including extensive 1D and 2D NMR techniques. Compounds 1-3 were evaluated for their anti-tobacco mosaic virus (Anti-TMV) activity. The results showed that compounds 1-3 showed potential anti-TMV activities with inhibition rates of 34.5%, 36.3%, and 57.2% at the concentration of 20 µM, respectively. These rates are higher than that of positive control.

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Published online: 12th March, 2019

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-19-14033
Synthesis of 1,2-Benzothiazole-3(2H)-thione 1,1-Dioxides by DBU-Promoted Cyclization of 2-(Aminosulfonyl)-N-methylbenzothioamide Derivatives

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

An efficient method for the preparation of 2-alkyl-1,2-benzothiazole-3(2H)-thione 1,1-dioxides has been developed. Thus, the reaction of 2,N-dilithio derivatives of N-alkylbenzenesulfonamides with methyl isothiocyanate affords 2-[(alkylamino)sulfonyl]-N-methylbenzothioamides, which are treated with a catalytic amount of DBU in refluxing toluene to provide the desired products in moderate to good yields.

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Published online: 7th March, 2019

Communication | Regular issue | Prepress
DOI: 10.3987/COM-19-14035
Substitution of a Haloquinone by Phenols under Pyridine-Free Conditions: Synthetic, Mechanistic, and Solid-State Considerations Involving 2,3-Dichloro-1,4-naphthoquinone

Nolan J. Blythe, Kristin M. Hutchins, Joshua R. Carpenter, Taylor W. Cox, Andrew M. Johnson, Leonard R. MacGillvray, and Jay Wm. Wackerly*

*Department of Chemistry, Central College, Pella, IA 50129, U.S.A.

Abstract

Benzoquinones fused to heterocycles, like most benzoquinones, have the potential for a wide-array of applications but their inherent reactivity can present a synthetic dilemma. The issue is that a synthesis may target one desired outcome, yet yield a range of side products. In efforts to understand the reaction pathways of haloquinone substitution, while minimizing undesired product formation, four examples of reactions between 2,3-dichloro-1,4-naphthoquinone and phenolic nucleophiles are presented. Two of the products were confirmed and analyzed by X-ray crystallography. The reaction with orcinol was optimized for yield and investigation of this mechanism indicates a novel pathway under pyridine-free conditions.

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Published online: 4th March, 2019

Paper | Regular issue | Prepress
DOI: 10.3987/COM-18-14028
One-Pot Solvothermal Synthesis and X-Ray Structure of a Methylated Terpyridine Derivative as DNA Binder and Anticancer Agent

Yihui Jiang, Keke Chai, Yi Sun, Qiwen Pang, Xiaoli Liu, Min Shi, Jing Wang, Jie Wei, Da Liu, and Jintao Wang*

*Jiangxi Provincial Key Laboratory of Drug Design and Evaluation, School of Pharmacy, Jiangxi Science & Technology Normal University, Nanchang 330013, China

Abstract

A new terpyridine derivative [mterpy]I {(mterpy = 2-[4-(4-methylphenyl)-2,2'-bipyridin-6-yl]-1-methylpyridinum) iodide} was synthesized and characterized by single crystal X-ray crystallography, and π-π stacking interaction was detected in the structure. The new methylated polypyridine ligand [mterpy]I was easily obtained under solvothermal condition. Meanwhile, the product exhibited evident in vitro antiproliferation activity towards cancer cells in methyl-thiazolyl-tetrazolium (MTT) assays.

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Published online: 27th February, 2019

Review | Special issue | Prepress
DOI: 10.3987/REV-18-SR(F)1
Design and Synthesis of Artificial Ladder-Shaped Polyethers for Exploring Biological Functions

Tohru Oishi*

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

Abstract

Ladder-shaped polyethers (LSPs) are marine natural products produced by dinoflagellates. The unique molecular structure and interesting biological activities have attracted considerable attention of the synthetic community. On the other hand, artificial ladder-shaped polyethers (ALPs) have been designed and synthesized for exploring biological functions. In this review, design and synthesis of ALPs are summarized focusing on the development of synthetic strategies and methodologies.

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Published online: 27th February, 2019

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)99
Diastereo–/Enantioselective Diels–Alder Synthesis of 14β-Hydroxysteroid Scaffolds: A Combined Experimental and DFT Study

Clovis Peter, Philippe Geoffroy, Takatsugu Murata, Takayuki Tonoi, Isamu Shiina,* and Michel Miesch*

*Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan

Abstract

Natural, non-natural and ent-14β-hydroxyandrostane derivatives closely related to the cardenolide and bufadienolide skeletons were readily available through highly diastereo-/enantioselective Diels–Alder reactions calling for high pressure or Lewis acid activation. Moreover, in the presence of (R)- or (S)-carvone as chiral dienophile, the Diels–Alder reaction took place under chemodivergent parallel kinetic resolution control. Based on experimental and DFT studies, reasonable mechanism insights were postulated to explain the concave/convex and endo/exo selectivities observed for the formation of the different Diels–Alder and Diels–Alder–Michael adducts.

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Published online: 27th February, 2019

Paper | Regular issue | Prepress
DOI: 10.3987/COM-19-14037
Biological Activity of Sinapic Acid Derivatives Isolated from Raphanus sativus

Takaya Ishida, Aki Hasebe, Xingyun Zhao, and Hideyuki Shigemori*

*Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572 Japan

Abstract

Radish sprout (Raphanus sativus) is a vegetable sprout that contains various sinapic acid derivatives. In this study, three sinapic acid derivatives 1-3 isolated from R. sativus, sinapic acid (4), and compounds 5-7, derived from the methylation of compounds 2-4, respectively, were used to investigate the structure-activity relationship for various bioactivities. Compounds with a number of sinapoyl and phenolic hydroxyl groups were found to have antioxidant and angiotensin converting enzyme (ACE) inhibitory activities. In addition, the sugar domains and the phenolic hydroxyl group in sinapoyl group is related to α-glucosidase inhibitory activity. Therefore, these sinapic acid derivatives are promising candidates to move forward to in vivo studies for the treatment of lifestyle-related diseases such as diabetes and hypertension.

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Published online: 25th February, 2019

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)83
Study toward an Asymmetric and Catalytic Synthesis of Koumine

David Reyes Loya, Jacques Maddaluno, and Michaël De Paolis*

*Normandie Université, UNIROUEN, INSA de Rouen, CNRS, Laboratoire COBRA (UMR 6014 & FR 3038), 76000 Rouen, France

Abstract

A synthetic study of koumine, a natural product with a densely functionalized and inspiring heterocyclic skeleton, was conducted by exploring a strategy of desymmetrization of 1,3-cyclohexanedione by an intramolecular vinylation reaction of an enolate under palladium catalysis to give a strained bridgehead 1,3-cyclohexanedione scaffold. In the course of the study, a domino ring expansion was discovered and developed.

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Published online: 25th February, 2019

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)82
The Effect of Lithium Ion on the Stereoselectivity of the Intramolecular Michael Addition of an N-Aryl-Sulfoximine Anion

Aswin Garimalla, Quin Long, Christopher J. Cramer,* and Michael Harmata*

*Department of Chemistry, University of Missouri-Columbia, Columbia, MO 65211, USA.

Abstract

The stereochemical outcome of the intramolecular Michael addition of a sulfoximine carbanion to a Z-configured α,β-unsaturated ester is dependent on lithium ion coordination between the oxygen on the sulfoximine and the carbonyl oxygen of the ester, based on both experimental and computational studies. Formally, this leads to a more sterically congested structure than might otherwise be preferred. Indeed, addition of HMPA, a substance capable of effective solvation of lithium cations, changes the stereochemical course of the reaction dramatically.

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Published online: 22nd February, 2019

Review | Regular issue | Prepress
DOI: 10.3987/REV-18-901
Advances in the Synthesis of 1,2,4-Triazolo[1,5-a][1,3,5]triazines (5-Azapurines) and Their Biological Activity

Koon Kee Kow and Anton V. Dolzhenko*

*School of Pharmacy, Monash University Malaysia, Jalan Lagoon Selatan, Bandar Sunway, Selangor Darul Ehsan 47500, Malaysia

Abstract

The 1,2,4-triazolo[1,5-a][1,3,5]triazine system has been recognized as a promising scaffold for drug development purposes. The isosteric relationship between this skeleton and purines plays an important role in the research towards the development of bioactive 1,2,4-triazolo[1,5-a][1,3,5]triazine derivatives. This review discusses recently developed strategies for the synthesis of 1,2,4-triazolo[1,5-a][1,3,5]triazines and advances achieved in studies on biological activity of compounds constructed using this skeleton

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Published online: 22nd February, 2019

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-18-14022
Synthesis of 2-Substituted Indole with Hantzsch Ester Catalyzed by Palladium

Yanan Li,* Bo Wang, and Ruiguang Xing*

*School of Materials and Metallurgy, Inner Mongolia University of Science and Technology, No.7 Arding Street, Kun District, Baotou 014010, China

Abstract

An efficient reductive cyclization of o-nitrobenzyl ketone compounds was achieved by using a Hantzsch 1,4-dihydropyridine ester as a biomimetic reducing agent in the presence of catalytic palladium on carbon. 2-Substituted indoles were obtained in good yields. Investigation of the mechanism suggests that palladium hydride promotes the reduction of nitro group, and acetic acid was beneficial for the loss of water to produce the intended product. This reaction system can not only broaden the use of Hantzsch 1,4-dihydropyridine ester, but it also provides a novel approach for preparing indole compounds.

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Published online: 20th February, 2019

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)101
1,2-cis-Selective Formation of a Unique Amino-Containing Amino Glycoside by Endocyclic Cleavage Strategy

Shino Manabe* and Yukishige Ito*

*Synthetic Cellular Chemistry Laboratory, RIKEN, Hirosawa, Wako, Saitama 351-0198, Japan

Abstract

2-Acetamido-4-amino-2,4,6-trideoxy-α-D-galactopyranoside (AAT), a unique aminated sugar unit, is often found in zwitterionic polysaccharides. Stereoselective formation of the 1,2-cis linkage of these unique sugar derivatives was achieved by an anomerization reaction based on an endocyclic cleavage process.

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Published online: 20th February, 2019

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)95
Construction of Pinpoint-Fluorinated Benzothiophene Frameworks Using Palladium-Catalyzed Cyclization of o-(Fluorovinyl)phenyl-substituted Thiophenes

Kohei Fuchibe, Nobushige Tsuda, Kento Shigeno, and Junji Ichikawa*

*Division of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Ten-nodai, Tsukuba-shi, Ibaraki 305-8571, Japan

Abstract

o-(2,2-Difluorovinyl)phenyl- or o-(1,2,2-trifluorovinyl)phenyl-substituted thiophenes underwent palladium(II)-catalyzed Friedel–Crafts-type cyclization on the fluorovinyl moieties to construct regioselectively monofluorinated or difluorinated benzothiophene frameworks (pinpoint-fluorinated naphtho[b]thiophenes). The cyclization of less nucleophilic 2-substituted thiophenes was effectively promoted by the addition of a CuOTf complex. Cyclization was also conducted in a tandem process, which facilitated the rapid synthesis of higher-order pinpoint-fluorinated PAHs (polycyclic aromatic hydrocarbons) bearing thiophene rings. Furthermore, cyclization was applied to the corresponding furan systems, which led to pinpoint-fluorinated naphtho[b]furans.

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Published online: 18th February, 2019

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)102
Synthesis of Di(3-thienyl)benzoporphyrin

Tetsuo Okujima,* Kota Muramatsu, Shigeki Mori, Masayoshi Takase, and Hidemitsu Uno

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

Abstract

We have successfully synthesized 2,3-di(3-thienyl)benzo[b]porphyrin based on retro DielsAlder reaction of bicyclo[2.2.2]octadiene(BCOD)-fused porphyrin and investigated its photoisomerization reaction.

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Published online: 18th February, 2019

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-18-S(F)80
Synthesis of Alkenyl Sulfones Containing Norbornene Moiety

Sambasivarao Kotha* and Rama Gunta

*Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai - 400076, India

Abstract

Various cyclopropane containing alkenyl sulfone derivatives were synthesized starting with a readily available Diels–Alder adducts.

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Published online: 15th February, 2019

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)94
Synthesis of a Poly-Heterocyclic Tetra-Substituted Alkene via a Palladium-Catalyzed Four-Fold Domino Reaction for the Design of Polymeric Molecular Switches

Taukeer A. Khan and Lutz F. Tietze*

*Institute of Organic and Biomolecular Chemistry, University of Goettingen, Tammannstrasse 2, 37077 Goettingen, Germany

Abstract

A facile synthesis of a complex poly-heterocyclic tetrasubstituted alkene 4 with intrinsic helical chirality containing two acrylate moieties suitable for polymerization is described. Compound 4 can act as a molecular switch and was prepared via a palladium-catalyzed four-fold domino reaction including two Sonogashira reactions and two domino-carbopalladation/CH-activation reactions.

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Published online: 15th February, 2019

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)97
Optimized Synthesis and Solid State Investigations on the Drug Candidate Encenicline Hydrochloride

Gerhard Laus, Sandro Neuner, Ramona Metz, Thomas Müller, Volker Kahlenberg, Thomas Gelbrich, Sven Nerdinger,* Erwin Schreiner, Verena Adamer, Klaus Wurst, and Herwig Schottenberger

*Global Portfolio, Sandoz GmbH, Biochemiestrasse 10, 6250 Kundl, Austria

Abstract

For the production of drug substances a robust, scalable process delivering the active pharmaceutical ingredient (API) in excellent chemical and polymorphic purity is required. For this purpose we developed a novel imidazole-mediated one-pot procedure for the preparation of encenicline hydrochloride monohydrate, which crystallizes directly from the reaction mixture as pure non-hygroscopic polymorph (Form I). Solid state studies revealed a series of additional new physical forms for which crystal structures have been determined by single crystal X-ray diffraction.

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Published online: 14th February, 2019

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)100
Preparation of Tricyclic Analog as CDE Ring Model of Renieramycin Marine Natural Product by Novel Photo-Induced Transformation of 6-Methoxy 1,2,3,4-Tetrahydroisoquinoline-5,8-dione

Masashi Yokoya, Shohei Takahashi, and Naoki Saito*

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

Abstract

2-Acetyl-6-[(benzyloxy)methyl]-9-methoxy-8-methyl-11,11a- dihydro-2H-pyrazino[1,2-b]isoquinoline-1,4,7,10(3H,6H)-tetraone (11a) was prepared as the CDE ring model of renieramycins, and its novel photo-induced transformation was demonstrated to construct a 1,3-dioxol ring.

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Published online: 14th February, 2019

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)103
Synthesis of Furan-Fused Silole and Phosphole by One-Pot Halogen Dance/Homocoupling of Bromofurfural Derivative

Kentaro Okano,* Yuki Murase, and Atsunori Mori

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

Abstract

Synthesis of a furan-fused silole and phosphole was achieved through a one-pot halogen dance/homocoupling of a bromofurfural derivative followed by the formation of the silole and phosphole skeleton.

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Published online: 13th February, 2019

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)87
Asymmetric Synthesis of t-Butyl 3-Alkyl-oxindole-3-carboxylates via Chiral Phosphoric Acid Catalyzed Desymmetrization of Di-t-butyl 2-Alkyl-2-(2-aminophenyl)malonates

Kyoji Ishida, Masahiro Shimizu, Yu-suke Yamai, Itaru Natsutani, Shinichi Uesato, Yasuo Nagaoka, and Takaaki Sumiyoshi*

*Department of Life Science and Biotechnology, Faculty of Chemistry, Materials and Bioengineering, Kansai University, Yamate-cho 3-3-35, Suita, Osaka, 564-8680, Japan

Abstract

We describe the asymmetric desymmetrization of di-t-butyl 2-alkyl-2-(2-aminophenyl)malonates to prepare enantioenriched t-butyl 3-alkyl-oxindole-3-carboxylates using (S)-TRIP, a chiral phosphoric acid. Optimization study increased the enantioselectivity up to 66% ee.

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Published online: 13th February, 2019

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-18-S(F)91
Synthetic Study of an Intermediates towards Paracentrone

Taiki Kaneyama, Kazumi Fujimaru, Mami Takemura, Kizuku Hasegawa, Masahiro Hamada, Takao Kishimoto, Daisuke Urabe, and Noriyuki Nakajima*

*Faculty of Engineering, Toyama Prefectural University, 5180 Kurokawa, Kosugi, Toyama 939-0398, Japan

Abstract

Paracentrone (1), the second naturally occurring C31-methyl ketone apocarotenoid from fucoxanthin (2), was first isolated from the sea urchin Paracentrotus lividus. In this study, we focused on this carotenoid metabolite and report on a synthetic approach towards (3E)-(5R)-[(2R,4S)-2-hydroxyl-4-(tert-butyldimethylsilyl)oxy-2,6,6-trimethylcyclohexylidene]-1-iodo-4-methyl-1,3,5-hexatriene (5), a synthetic intermediate towards 1. This was obtained from epoxy acetylene (11) via (2E)-(4R)-[(2R,4S)-2-hydroxyl-4-(tert-butyldimethylsilyl)oxy-2,6,6-trimethylcyclohexylidene]-3-methylpenta-2,4-diene-1-ol (7).

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Published online: 13th February, 2019

Paper | Regular issue | Prepress
DOI: 10.3987/COM-19-14031
Synthesis of 1-Methoxyindoles and Related Analogs of Pimprinine, (±)-Chelonin A and B, Based on 1-Hydroxyindole Chemistry

Kazuko Aoki, Yoshiyuki Nagahama, Katsuko Sugaya, Yuki Maeda, Haruhiko Sato, Kyoko Nakagawa (Goto), and Masanori Somei*

*Noto Marine Laboratory, Institute of Nature and Environmental Technology, Faculty of Pharmaceutical Sciences, Graduate School of Natural Science and Technology, Kanazawa University, 56-7 Matsuhidai, Matsudo-shi, Chiba 270-2214, Japan

Abstract

The total synthesis of pimprinine, (±)-chelonin A and B, and their analogs are achieved based on 1-hydroxyindole chemistry.

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Published online: 8th February, 2019

Communication | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)77
Tripeptide-catalyzed Asymmetric Aldol Reaction of Trifluoromethylated Aromatic Ketones with Acetone

Kazumasa Kon, Yoshihito Kohari,* and Miki Murata

*School of Earth, Energy and Environmental Engineering, Faculty of Engineering, Kitami Institute of Technology, 165 Koen-Cho, Kitami, Hokkaido 090-8507, Japan

Abstract

The development of H-Pro-Gly-Ala-OH (3d) to realize an inexpensive and simple organocatalytic system for the direct asymmetric aldol reaction of trifluoromethylated aromatic ketone 1 with acetone was achieved. The 3d-catalyzed aldol reaction of 1a1j provided various aldol adducts 4a4j with up to 81% yield and 77% ee. An investigation of the transition state via DFT calculations revealed that hydrogen bonding was important for the revelation of the enantioselectivity.

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125 data found. 1 - 30 listed Next Last