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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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Published online: 12th June, 2018

Short Paper | Regular issue | Prepress
DOI: 10.3987/COM-18-13912
Synthesis and Electrochemical Properties of 2,2’-Biguaiazulene-Based 1,2-Dithiin and Thiophene

Ohki Sato* and Ryuto Sakai

*Department of Chemistry, Graduate School of Science and Engineering, Saitama University, Shimo-okubo 255, Sakura-ku, Saitama 338-8570, Japan

Abstract

The synthesis of diguaiazuleno[3,2-c:2’,3’-e][1,2]dithiin was achieved by the reaction of 2,2’-biguaiazulene with disulfur dichloride/imidazole as a sulfuration reagent. Thermolysis of the dithiin afforded the corresponding desulfurized compound, diguaiazuleno[3,2-b:2’,3’-d]thiophene. Cyclic voltammetry of the S-heterocycles showed one reversible wave at the reduction region, respectively.

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Published online: 8th June, 2018

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(T)92
Polymorphism of Macrocyclic Oligothiophehe 8-Mers

Hideyuki Shimizu, Tahmina Haque, Masataka Takashika, Hiroyuki Otani, and Masahiko Iyoda*

*Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan

Abstract

Macrocyclic oligothiophene 8-mer E,E-8T6A composed of eight thienylene, six ethynylene, and two vinylene units exhibits unique polymorphism. In the solid state, E,E-8T6A formed nanostructured polymorphs such as single crystals, fibers, long and short rods, and square tubes depending on the solvent used for crystallization. In contrast, E-8T7A with one vinylene unit and 8T8A without vinylene unit afforded single crystals, microcrystalline, and short rods in the solid state. Morphological difference between E,E-8T6A and E-8T7A/8T8A is due to the flexibility of the macroring of E,E-8T6A with two vinylene units, and the shape-persistent but rather flexible E,E-8T6A forms various polymorphs in the solid state.

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Published online: 5th June, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(T)93
Notable Difference between Tetrabutylammonium Fluoride and Organic Superbases as Triggers for The Chemiluminescent Decomposition of Bicyclic Dioxetanes Bearing A 4-(N-Phenylbenzimidazol-2-Yl)-3-Hydroxyphenyl Moiety

Nobuko Watanabe, Koh Kumagai, Rei Ohtuka, Ayu Wakatsuki, Hisako K. Ijuin, Yoshio Kabe, and Masakatsu Matsumoto*

*Department of Chemistry, Faculty of Science, Kanagawa University, 2946 Tsuchiya, Hiratsuka 259-1293, Japan

Abstract

Chemiluminescent decomposition of bicyclic dioxetanes 3a−3c bearing a 4-(N-phenylbenzimidazol-2-yl)-3-hydroxyphenyl moiety was effectively induced by organic superbases, BTPP [(tert-butylimino)tris-(pyrrolidino)phosphorene], TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene), MTBD(7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene), DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), and TMG (tetramethylguanidine), as well as TBAF in acetonitrile. Dioxetane 3c bearing a 3,5-dihydroxyphenyl moiety showed diverse chemiluminescence profiles depending on the base used. BTPP caused chemiluminescent decomposition due to the di-oxido anion of dioxetane, while DBU and TMG induced chemiluminescence from the mono-oxido anion of dioxetane. On the other hand, TBAF caused effective chemiluminescence due to the mono-oxido anion, though it acted as a stronger base than BTPP with regard to the rate of decomposition of 3c.

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Published online: 4th June, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(T)85
Synthetic Studies Toward Isoschizogamine: Construction of Pentacyclic Core Structure

Kenji Sugimoto, Hiroaki Fujiwara, Akihiro Takada, Dong-Gil Kim, Hirofumi Ueda, and Hidetoshi Tokuyama*

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

Abstract

Development of a concise construction of the pentacyclic core skeleton of isoschizogamine was described. Tetracyclic A,B,D,F-rings structure was assembled by intramolecular aza-Diels–Alder reaction via an ortho-iminoquinone methide intermediate. The C-ring was formed by oxidation of the benzylic position with a combination of Cr(CO)6 and t-BuO2H, followed by the introduction of an aminoethyl side chain, C–H oxidation of the lactam ring with CrO3 and n-Bu4NI, and final cyclization to construct the cyclic aminal moiety.

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Published online: 4th June, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)6
Synthesis and Cytotoxicity of Novel Bis-Ellipticines and Bis-Isoellipticines

Judy A. Obaza-Nutaitis and Gordon W. Gribble*

*6128 Burke Laboratory, Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, U.S.A.

Abstract

A series of bis-ellipticines 79 and bis-isoellipticines 1012 tethered through the indole nitrogen was synthesized and screened for antitumor cytotoxicity in the L-1210 murine leukemia assay. Activity was only displayed by 1,10-bis(6-ellipticinyl)-n-decane (8)

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Published online: 4th June, 2018

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)7
Total Synthesis of Haplacutines B and C

Noriki Kutsumura,* Keisuke Numata, Shiho Mosaki, and Takao Saito*

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

Abstract

The total synthesis of 4-quinolone alkaloids, haplacutines B and C, has been achieved. The synthetic highlights are chemoselective construction of a 2-alkyl-4-quinolone skeleton via intramolecular base-promoted cyclocondensation of ortho-alkylamidoacetophenone and stereoselective elongation of the dienol side chain via the Stille coupling

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Published online: 1st June, 2018

Review | Special issue | Prepress
DOI: 10.3987/REV-18-SR(T)4
Cycloaddition Reactions of N-Alkyl-alpha,beta-unsaturated Imines: Facile Preparation of Azaheterocycles for Synthesis and Biological Applications

Ambara R. Pradipta, Liliya Latypova, Dilyara Chulakova, Ivan Smirnov, Almira Kurbangalieva, and Katsunori Tanaka*

*Biofunctional Synthetic Chemistry Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan

Abstract

In this review, we will describe the utilization of formal [4 + 4] cycloaddition reaction of N-alkyl-,-unsaturated imines derived from acrolein and biogenic alkylamines to synthesize 2,6,9-triazabicyclo[3.3.1]nonanes and 1,5-diazacyclooctanes. We also include here a new structural data of 1,5-diazacyclooctane determined by X-ray crystallography. Biological examination of 1,5-diazacyclooctanes revealed for the first-time its role in inhibition of amyloid- (A) 1-40 fibrillization. Eventually, we also found that when substituted or unsubstituted acrolein is reacted with chiral ethanolamine in the presence of formaldehyde, then hexahydropyrimidines or 1,3,5-triazacyclooctanes were produced in high yield and stereoselectivity through formal [4 + 2] or [4 + 2 + 2] cycloaddition reactions. Lastly, simple functional group manipulations of the cycloaddition products can be used to synthesize chiral 1,3-diamines, which could not be simply accessed by other methods.

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Published online: 31st May, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(T)31
Facile Synthesis of Indolelactones using Mn(III)-Based Oxidative Substitution-cyclization Reaction

Takeshi Inoue and Hiroshi Nishino*

*Department of Chemistry, Graduate School of Science and Technology, Kumamoto University, Kurokami 2-39-1, Chûou-Ku, Kumamoto 860-8555, Japan

Abstract

Based on the oxidation of indole with Mn(OAc)3 in the presence of 1,1-diarylethenes affording 3-vinyl-substituted indoles, a similar oxidation using indole-2-carboxylic acids was evaluated in order to effectively introduce the substituent group to the C-3 position of the indolecarboxylic acids. The coupling reaction followed by oxidative cyclization smoothly proceeded at room temperature in an AcOH-HCO2H mixed solvent to give the desired indolelactones in high yields. The reaction details, the structure determination of the products and a brief reaction mechanism are described.

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Published online: 31st May, 2018

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(T)80
Facile Synthesis of Stable Uracil-Iodonium(III) Salts with Various Counterions

Naoko Takenaga,* Shohei Ueda, Takumi Hayashi, Toshifumi Dohi, and Shinji Kitagaki

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

Abstract

Aryliodonium(III) salts, one of the useful and important classes of hypervalent iodine compounds, have a wide range of applicability, i.e., photoacid generator, active bactericides, and coupling agents for reacting a wide range of nucleophiles even under metal-free conditions. In this report, we present an approach to the design of stable uracil-iodonium(III) salts with various counterions. Uracil is an important substructure that exists in many biologically active compounds and the introduction of such a moiety in iodonium(III) salts would be of high utility in organic chemistry.
This paper is dedicated to Professor Kiyoshi Tomioka on the occasion of his 70th birthday.

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Published online: 30th May, 2018

Review | Regular issue | Prepress
DOI: 10.3987/REV-18-882
Eudistomin U, Isoeudistomin U, and Related Indole Compounds: Synthesis and Biological Activity

Alexandra A. Kolodina and Olga V. Serdyuk*

*Department of Chemistry and Pharmacy, University of Erlangen-Nuremberg, Nikolaus-Fiebiger-Str. 10, Erlangen 91058, Germany

Abstract

Eudistomin U and isoeudistomin U are important derivatives of β-carboline, tryptophan-derived metabolites. These natural products and related 2-substituted 1,2,3,4-tetrahydroeudistomins U demonstrate antibacterial, antimalarial, and anticancer activities, as well as a DNA-binding ability and strong KSP inhibition, that makes them very attractive targets for synthetic chemists. This manuscript highlights advances in the synthesis of eudistomin U, isoeudistomin U, their derivatives, and related compounds bearing an indole unit. A detailed discussion of biological activities, including structure-activity relationships, and future prospects, are also presented.

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Published online: 30th May, 2018

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(T)53
Design and Synthesis of A DNA-Like Structure Composed of Alkynyl C-Nucleotide with 2-Aminopyrimidin-4-one as a Nucleobase

Kurosaki Fumihiro, Junya Chiba,* and Masahiko Inouye*

*Graduate School of Medicines and Pharmaceutical Sciences for Research, Toyama University, 2630 Sugitani, Toyama, Toyama 930-0194, Japan

Abstract

A heterocyclic compound, 2-aminopyrimidin-4-one, was found to be a new candidate of a non-natural nucleobase that forms a novel base pair by self-dimerization. 2-Aminopyrimidin-4-one was connected to a deoxyribose through an acetylene linkage. The non-natural nucleoside was derivatized to its phosphoramidite that could be subjected to a conventional solid-phase DNA synthesis. The solid-phase auto-synthesis successfully afforded a non-natural DNA-like oligomer bearing 2-aminopyrimidin-4-one as a nucleobase. The synthetic oligomer exhibited reversible formation of a higher-order structure that would be a duplex like natural DNA. The present study means creation of a novel artificial DNA-like system with unordinary odd numbers of genetic alphabets.

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Published online: 29th May, 2018

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(T)82
Efficient Synthesis of t-Butyl 3-Alkyl-N-Hydroxy-Oxindole-3-Carboxylates from Di-t-Butyl 2-Nitrophenyl-Malonates

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

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

Abstract

A selective and efficient synthesis of t-butyl 3-alkyl-N-hydroxy- oxindole-3-carboxylates from di-t-butyl 2-nitrophenylmalonates is described. A tandem reduction-cyclization approach involving reduction of di-t-butyl 2-methyl-(2-nitrophenyl)malonate to di-t-butyl 2-(2-(hydroxyamino)phenyl)-2-methylmalonate followed by accelerated cyclization reaction using a combination of Rh/C and hydrazine monohydrate smoothly and selectively afforded the N-hydroxy-oxindole scaffold. This methodology was successfully applied to gram-scale-synthesis of the t-butyl N-hydroxy-3-methyl-oxindole-3-carboxylate 1 without silica gel column chromatographic separation step.

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Published online: 28th May, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(T)64
Asymmetric Synthesis of O-Methylneferine

Katsumi Nishimura,* Shinji Horii, and Takao Tanahashi

*Organic Chemistry, Kobe Pharmaceutical University, 4-19-1 Motoyamakita-machi, Higashinada-ku, Kobe 658-8558, Japan

Abstract

Diastereoselective Pictet–Spengler reaction of 2-arylethylamine bearing an N-(R)-1-(1-naphthyl)ethylcarbamoyl group with arylacetaldehyde gave 1-benzyltetrahydroisoquinoline in good yield with moderate diastereoselectivity. The reaction was applied to asymmetric synthesis of O-methyl derivative of neferine, an alkaloid of the lotus embryo, Nelumbo nucifera Gaertner.

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Published online: 23rd May, 2018

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(F)3
Visible-Light-Promoted Se-Arylation of Diaryl Diselenides with 2-Phenylimidazopyridines in the Presence of Ammonium Iodide: Synthesis of 2-Phenyl-3-(Arylselanyl)Imidazo[1,2-α]Pyridines

Yuki Murata, Keiko Kanasaki, Kaito Kondo, Naoki Kakusawa, Mio Matsumura, and Shuji Yasuike*

*School of Pharmaceutical Sciences, Aichi Gakuin University, 1-100 Kusumoto-cho Chikusa-ku Nagoya city 464-8650, Japan

Abstract

Photoreaction of diaryl diselenides and 2-phenylimidazo[1,2-a]pyridine in the presence of ammonium iodide (20 mol%) using blue LED light led to the formation of 3-(arylselanyl)imidazopyridines in good-to-excellent yields under aerobic conditions. By using various diselenides, this reaction efficiently introduces the selanyl group at the 3-position of the imidazopyridine scaffold

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Published online: 21st May, 2018

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(T)79
Total Synthesis of Coriariin B

Hitoshi Abe,* Yoshiyasu Kato, Haruka Imai, and Yoshikazu Horino

*Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan

Abstract

The total synthesis of coriariin B (1), which is a type of ellagitannin, and originally obtained from the leaves of Coriaria japonica, was achieved by esterification between the glucose derivative and partially protected dehydrodigallic acid (5). The HHDP (hexahydroxydiphenoyl) unit was constructed by the oxidative phenol coupling reaction in a stereoselective manner.

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Published online: 18th May, 2018

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(T)90
5-((3-Bromoallyl)Sulfonyl)-1H-Tetrazoles for Bromodiene Synthesis

Takuro Suzuki, Seiya Fukagawa, Tatsuhiko Yoshino, Masahiro Anada, and Shigeki Matsunaga*

*Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita 12 Nishi 6, Kita-ku, Sapporo, Hokkaido 060-0812, Japan

Abstract

Reagents for one-step construction of conjugated bromodienes from aldehydes are described. Various 1-alkyl- and 1-aryl-tetrazoyl bromoallylic sulfones were synthesized and evaluated in bromodiene synthesis. 1-Alkyl-tetrazoyl sulfones selectively afforded (1E,3Z)-bromodienes, while 1-aryl-tetrazoyl sulfones resulted in low selectivity.

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Published online: 18th May, 2018

Paper | Special issue | Prepress
DOI: 10.3987/COM-17-S(T)4
Palladium-Catalyzed Selective Formation of Substituted Pyrroles from Alkene-tethered Cyclic Oxime Esters

Kazuhiro Okamoto,* Tomohiro Oda, Takuya Shimbayashi, and Kouichi Ohe*

*Deparment of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoudai-katsura, Nishikyo, Kyoto 615-8510, Japan

Abstract

Isoxazol-5(4H)-ones were used as nitrene precursors for the selective formation of trisubstituted pyrroles by applying a palladium-catalyzed decarboxylative ring-reconstruction method. The use of bulky biaryl-type monophosphine ligands was effective for improving the selectivity. Deuterium-labeling experiments suggested a mechanism involving -hydride elimination followed by reductive elimination from an aza--allyl intermediate.

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Published online: 18th May, 2018

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-18-S(T)45
Preparation of Optically Active 2,2-Disubstituted 5-Hydroxychromenes by the Enzymatic Resolution of Racemic Esters

Mika Kainuma, Ai Yamada, Kazuaki Katakawa, and Takuya Kumamoto*

*Department of Synthetic Organic Chemistry, School of Pharmaceutical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan

Abstract

Enzymatic kinetic resolution of racemic esters of 2,2-disubstituted 5-hydroxychromenes was examined. Transesterification of acetate using Amano Lipase PS in the presence of t-BuOH was most effective to give the corresponding optically active acetate in 18% yield and 95% ee. The absolute configuration of the acetate was determined as R based on the conversion to teretifolione B with natural absolute configuration.

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Published online: 18th May, 2018

Communication | Special issue | Prepress
DOI: 10.3987/COM-18-S(T)81
Efficient One-Pot Synthesis of Substituted Oxazoles from 3-Trimethylsilylpropargylic Alcohols and Amides by Gold-Catalyzed Substitution Followed by Cycloisomerization

Nobuyoshi Morita,* Aoi Sano, Ayako Sone, Shino Aonuma, Arisa Matsunaga, Yoshimitsu Hashimoto, and Osamu Tamura*

*Laboratory of Organic Chemistry, Pharmaceutical Sciences, Showa Pharmaceutical University, 3-3165, Higashi-tamagawagakuen, Machida, Tokyo 194-8543, Japan

Abstract

3-Trimethylsilylpropargylic alcohols 1, on treatment with amides 2 in the presence of catalytic amounts of cationic gold(III), underwent propargylic substitution followed by cycloisomerization. The key of the cycloisomerization, in which the key feature is the β-cation-stabilizing effect of the silicon atom of 3-trimethylsilyl-propargylic alcohols 1.

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