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Published online: 29th March, 2021

Review | Special issue | Prepress
DOI: 10.3987/REV-20-SR(K)8
Recent Development on the Ring Transformation Reactions: Synthesis of Functionalized Benzenes, N-Heterocycles and Fused Ring Systems

Priyanka B. Kole and Fateh V. Singh*

*Chemistry Division (SAS), VIT Chennai, Vandalur-Kelambakkam Road, Chennai, Tamil Nadu, India

Abstract

Ring transformation reactions using 2H-pyran-2-ones as valuable synthetic precursor with several nucleophiles for designing numerous interesting scaffolds is a growing field in synthetic organic chemistry. 2H-Pyran-2-ones has tendency to act as very good Michael acceptor and hence functions as good electrophile. The scope of 2H-pyran-2-ones has been explored for the synthesis of various molecules owning significant biological importance. Additionally, their synthetic potential has been discovered for the construction of interesting photophysically active molecules. From this point of view, the development of simple and environmental benign ring transformation strategy is a dynamic research field until today. This short review describes an overview of the most recent advances in ring transformation of functionalized 2H-pyran-2-ones into valuable aromatic scaffolds like functionalized benzenes, N-heterocycles and fused ring systems.

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Published online: 26th March, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-21-S(K)74
Decisive Effects of C-N Axial Chirality of Intermediary Enolates on the Stereochemical Course of β-Lactam Formation from β-Branched α-Amino Acid Derivatives via Memory of Chirality

Ryuichi Hyakutake, Tomoyuki Yoshimura, Takahiro Sasamori, Norihiro Tokitoh, Kazuhiro Morisaki, and Takeo Kawabata*

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

Abstract

Stereochemistry of β-lactam formation of β-branched β-amino acid derivatives via a MOC strategy was investigated. The 4-exo-trig cyclization of axially chiral enolates generated from l-threonine and l-allo-threonine derivatives proceeded predominately with inversion of the configuration at the newly formed tetrasubstituted carbon, irrespective of the chirality at the β-carbon of the β-lactam precursors. These results indicated that C–N axial chirality of the intermediary enolates generated from the α-amino acid derivatives has decisive effects on the stereochemical course of β-lactam formation even in the presence of an sp3-chiral center at the β-carbon.

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Published online: 23rd March, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)72
Claisen Rearrangement of 4-Allyloxy-1-p-methyxy benzylpyrazole and Synthesis of Pyrazole-Fused 7-Membered Lactones

Hayato Ichikawa,* Hiroki Takashima, and Shoichi Shimizu

*College of Industrial Technology, Nihon University, 1-2-1, Izumi-cho, Narashino, Chiba 275-8575, Japan

Abstract

Allyl 4-pyrazolyl ethers were subjected to the Claisen rearrangement that involved heating under microwave condition to prepare the corresponding products with regioselective allylation at 5-position of the pyrazoles in good yields. The rearrangement products were converted into 7-membered pyrazololactones having an oxygen atom at 4-position of pyrazole, via a hydroesterification reaction with Pd(OAc)2 and DPE-phos as ligand under 40 atm of CO/H2 (6:34) in moderate to excellent yields.

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Published online: 23rd March, 2021

Communication | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)68
Chloroamidation of Alkenes Using Sodium Hypochlorite Pentahydrate and Its Application to Synthesis of Aziridines

Masayuki Kirihara,* Kouta Adachi, Yugo Sakamoto, Kazuki Tujimoto, Sho Yamahara, Ryoji Matsushima, Yukou Namba, Kosuke Sato, Takashi Kamada, Yoshikazu Kimura, and Shinobu Takizawa*

*The Institute of Scientific and Industrial Research, Osaka University, 8-1, Mihogaoka, Ibaraki, Osaka 567-0047, Japan

Abstract

The reaction of alkenes with sodium hypochlorite pentahydrate (NaOCl·5H2O) and phosphoric acid (H3PO4) in nitrile solvents resulted in a chloroamidation reaction, producing -chloroamide derivatives in good yields without the use of a transition metal catalyst (up to 90%). N-Pivalazirizines were readily obtained from the resulting -chloroamide derivatives when they were reacted with lithium hexamethyldisilazide (LiHMDS).

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Published online: 18th March, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)55
Stereoselectivity of the Biginelli Reaction Catalyzed by Chiral Primary Amine: A Computational Study

Takayoshi Yoshimura, Maneeporn Puripat, Vudhichai Parasuk, and Miho Hatanaka*

*Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan

Abstract

The Biginelli reaction catalyzed by a chiral compound is one of the most effective ways to form bioactive heterocycle compounds. High enantioselectivity was obtained using primary amine with a chiral diamine backbone as a chiral catalyst. To elucidate the origin of the enantioselectivity, we investigated the reaction pathways of this catalytic reaction using the density functional theory. We also focused on the transition states of the rate-determining step leading different stereoisomers. The rate-determining step was the proton transfer process accompanying the cyclization of the substrate, which was mediated by the amide moiety of the catalyst, and the orientation of the amide moiety was the reason for the enantioselectivity.

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Published online: 15th March, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)50
Fasciospyrinadinone and Fasciospyrinadinol, Novel 3-Alkylpyridine Sesquiterpenoids from an Indonesian Marine Sponge, as Selective Growth Inhibitors of the Cancer Cells Under Nutrient Starvation

Hirokazu Matsumoto, Tomoya Hisa, Kazunari Toda, Ryosuke Ishida, Andi Setiawan, Masayoshi Arai, and Naoyuki Kotoku*

*College of Pharmaceutical Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga, 525-8577, Japan

Abstract

On the guidance of the bioassay using PANC-1 cells adapted to the glucose starvation, two novel pyridine sesquiterpenoids named fasciospyrinadinone (1) and fasciospyrinadinol (2) were isolated from the Indonesian marine sponge of Petrosaspongia sp. The chemical structures of the compounds were established on the basis of the 1D and 2D NMR spectra data. Then, we accomplished the first total syntheses of 1 and 2. Compound 1 showed selective growth inhibitory activity against PANC-1 cells adapted to glucose starvation, with IC50 value of 13 µM.

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Published online: 15th March, 2021

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)73
Large-Scale Synthesis of Thio-glucose-Conjugated Chlorin e6 for Photodynamic Therapy

Akihiro Nomoto,* Hiroaki Yamaguchi, Masato Masuda, Keisuke Hyakumura, Shintaro Kodama, Tomohiro Osaki, Yoshiharu Okamoto, Mamoru Tanaka, Hiromi Kataoka, Atsushi Narumi, Tomokazu Yoshimura, Shigenobu Yano, and Akiya Ogawa

*Engineering, Department of Applied chemistry, Osaka Prefecture University, Sakai, Osaka 593-8531, Japan

Abstract

Chlorin e6 is a heterocycle exhibiting spectral absorption in the 600–700 nm wavelength range used for photodynamic therapy (PDT). Herein, a sugar-conjugated chlorin e6 derivative was synthesized on a large scale. An alkyl spacer was fabricated by controlling the alkylation conditions between the thio-sugar and chlorin e6 and thio-glucose-conjugated chlorin e6 was successfully synthesized.

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Published online: 12th March, 2021

Review | Special issue | Prepress
DOI: 10.3987/REV-20-SR(K)6
Combined Brønsted-Base-Mediated Direct C-H Carboxylation of Heteroarenes with CO2

Masanori Shigeno,* Keita Sasaki, Kazuya Hanasaka, Itsuki Tohara, Kanako Nozawa-Kumada, and Yoshinori Kondo*

*Graduate School of Pharmaceutical Science, Tohoku University, 6-3 Aobayama, Sendai 980-8578, Japan

Abstract

This review article summarizes that the combined Brønsted-base system comprising LiO-t-Bu, CsF, and 18-crown-6 efficiently proceeds the direct carboxylation of electron-rich heteroarenes, such as benzothiophene and benzofuran, with CO2. Good functional group compatibility is displayed, allowing the use of Me, MeO, halogen, CN, ketone, and amide moieties. 3-Substituted indoles are also used for C-2 carboxylation, while double-carboxylation of 2-alkylheteroarenes is achieved by LiO-t-Bu and CsF.

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Published online: 12th March, 2021

Communication | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)71
Gold-Catalyzed Formal [3+2]Cycloaddition of p-Quinones and 1-Phenylpropenes in Ionic Liquid: Environmentally Friendly and Stereoselective Synthesis of 2,3-Dihydrobenzofuran Neolignans

Nobuyoshi Morita,* Kanae Ikeda, Hitomi Chiaki, Ryuto Araki, Kosaku Tanaka III, Yoshimitsu Hashimoto, and Osamu Tamura*

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

Abstract

Gold(III)-catalyzed formal [3+2] cycloaddition of p-quinones with 1-phenylpropenes in an ionic liquid, [EMIM][NTf2], enabled environmentally friendly, stereoselective synthesis of 2,3-dihydrobenzofuran neolignans in good yields. Moreover, the recycle of tThe gold catalyst in /ionic liquid was achievedcould be recycled at least five times, affording 2,3-dihydrobenzofuran in good yields.

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Published online: 9th March, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)70
Stereoselective Synthesis of (2S,3R)- and (2S,3S)- 2-Amino-3-(3,4-dihydroxyphenyl)-3-hydroxypropanoic Acid

Yoko Yasuno, Shunsuke Yamaguchi, Yuma Karita, Kenta Sakai, Hironori Okamura, Atsushi Nakayama, and Tetsuro Shinada*

*Graduate School of Science, Osaka City University, Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan

Abstract

(2S,3R)- and (2S,3S)-2-amino-3-(3,4-dihydroxyphenyl)-3-
hydroxypropanoic acids
(ADHP) are often found in an unusual amino acid component of phomopsin B, ustiloxins, RA-IV, and MPC1001B. Herein, we would like to report stereoselective synthesis of (2S,3R)- and (2S,3S)-ADHP equivalents for the synthesis of ADHP containing natural products. The synthesis is characterized by the stereocontrolled construction of the (2S,3R)- and (2S,3S)-stereocenters starting from Garner’s aldehyde as a common starting material.

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Published online: 5th March, 2021

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)59
On the Order of Addition of Sodium Dispersion in Reductive Diborations of Stilbene and 1,2-Diphenylcyclopropane

Shuo Wang, Atsushi Kaga, and Hideki Yorimitsu*

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

Abstract

Two extreme methods to add sodium dispersion were investigated in the 1,2-diboration of stilbene and the ring-opening 1,3-diboration of 1,2-diphenylcyclopropane on a 20-mmol scale. Method 1 denotes that a substrate is added to a mixture of sodium dispersion and a boron electrophile. Method 2 denotes that sodium dispersion is slowly added to a mixture of a substrate and a boron electrophile. In these four cases, no significant differences were observed in the yields of the products and their syn/anti ratios, except for the diboration of stilbene by Method 1, wherein aggregation of sodium dispersion in the flask and 5% recovery of stilbene were observed. This information would be helpful in performing sodium-dispersion-mediated transformations on a large scale.

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Published online: 1st March, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)63
Design and Synthesis of Novel Orexin Antagonists via Structural Simplification of the Morphinan Skeleton

Sayaka Ohrui,* Yoko Irukayama-Tomobe, Yukiko Ishikawa, Masashi Yanagisawa, and Hiroshi Nagase

*C1232 Kanagawa Science Park R & D Building, Research Foundation ITSUU Laboratory, 3-2-1 Sakado, Takatsu-ku, 213-0012 Kawasaki, Kanagawa, Japan

Abstract

Herein, we report novel orexin antagonists with a spiro-type piperidine skeleton designed and synthesized via removal of the unnecessary sites of orexin 1 receptor (OX1R) antagonists with a morphinan skeleton for binding to OX1R. In addition, while decahydroisoquinoline compounds with an A-ring did not show antagonistic activity for OX1R, spiro-type piperidine compounds with a dihydroindene structure showed antagonistic activities. This suggests that the lipophilic site corresponding to the A-ring of the morphinan skeleton is important for determining the antagonistic activity toward OX1R.

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Published online: 1st March, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)52
A Fluorous Proline Catalyst Immobilized on Teflon® for Highly Stereoselective Asymmetric Aldol Reactions

Kazuki Ishihara, Riho Obayashi, Mizuki Ohira, Yuki Kobayashi, Kotaro Ishihara, Yamato Kato, Narisa Takeuchi, Risa Mizuno, Takayuki Shioiri, and Masato Matsugi*

*Faculty of Agriculture, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468-8502, Japan

Abstract

An immobilized fluorous-tagged proline catalyst and its application as a recycling system in highly stereoselective asymmetric aldol reactions is described. The introduction of acidic sulfonamide groups bearing multifluorous tags at the carboxy position proved to be more effective than the introduction of bulky substituents on the proline backbone to achieve high stereoselectivity. The Teflon®-immobilized proline catalyst could be recovered and reused at least five times while maintaining high levels of catalytic activity and stereoselectivity.

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Published online: 25th February, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)56
Regio-Complementary Preparation of 6- and 7-Fluoro-1,2,3,4-tetrahydroquinolines via the Cyclization of Catecholamines Followed by Deoxyfluorination

Kazuyuki Saito, Wang Zhou, Shohei Sato, Keita Takubo, Kazunori Furutsu, Ahmed A. B. Mohamed, Euis Maras Purwati, Takashi Ikawa, and Shuji Akai*

*Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamada-oka, Suita, Osaka 565–0871, Japan

Abstract

We herein report a regioselective preparation of 6- and 7-fluoro-1,2,3,4-tetrahydroquinolines by applying the deoxyfluorination strategy, developed by the authors. This method includes the cyclization of catecholamines bearing an N-protecting group to form 7-hydroxy-1-azaspiro[4.5]deca-6,9-dien-8-ones and 6,7-dihydroxy-1,2,3,4-tetrahydroquinolines followed by deoxyfluorination, in which the nature of the N-protecting group has a significant effect on both the cyclization and the regioselectivity of the deoxyfluorination reaction.

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Published online: 22nd February, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)54
Polyfluoroarene-Capped Thiophene Derivatives via Fluoride-Catalyzed Nucleophilic Aromatic Substitution

Kotaro Kikushima, Kana Matsuki, Yuna Yoneda, Takayuki Menjo, Kosuke Kaneko, Tomonori Hanasaki, and Toshifumi Dohi*

*College of Pharmaceutical Sciences, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga, 525-8577, Japan

Abstract

Arylthiophene derivatives are potential components of functional materials, including organic electronics. Herein, we describe a nucleophilic aromatic substitution reaction of polyfluoroarenes using silylthiophenes as nucleophiles in the presence of a catalytic amount of a fluoride salt. Various polyfluoroarene-capped thiophene derivatives were synthesized via double arylation under transition metal-free conditions. A fluoride ion activates a silylthiophene to trigger a nucleophilic aromatic substitution, subsequently affording the coupling product along with elimination of the fluoride ion, which serves as a promoter of the catalytic reaction.

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Published online: 22nd February, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)64
A Theoretical Study of Product Selectivity in Rhodium Catalyzed Oxidative Coupling Reaction Caused by the Solvation Effect

Masahiro Higashi,* Naoto Shibata, Suguru Takeno, Tetsuya Satoh, Masahiro Miura, and Hirofumi Sato*

*Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Kyoudai-katsura, Nishikyo, Kyoto 615-8510, Japan

Abstract

Solvation effects in the direct oxidative coupling of 1-phenylpyrazole with alkynes in the presence of rhodium catalyst was theoretically studied by means of the reference interaction site model self-consistent field with spatial electron density distribution (RISM-SCF-SEDD) method, which provides both of quantum chemical and statistical mechanical information on the solvation system. This reaction gives naphthalene and quinoline derivatives whose yields depend on the solvent environment. The computational results showed that the path for the naphthalene derivative is exothermic independently of solvent environment. On the other hand, the reaction energy of the reductive elimination for the quinoline derivative is considerably affected by solvation and endothermic in N,N- dimethylformamide (DMF) solution, indicating that the reaction is not preferable in DMF solution. The detailed analysis of solvation free energy and solvation structure are also reported.

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Published online: 17th February, 2021

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)61
Diastereo- and Enantioselective Intramolecular 1,6-C–H Insertion Reaction of Diaryldiazomethanes Catalyzed by Chiral Dirhodium(II) Carboxylates

Motoki Ito, Yuji Kondo, Ryosuke Namie, Yoshihiro Natori, Koji Takeda, Hisanori Nambu, Masahiro Anada,* Yasunori Yamamoto, and Shunichi Hashimoto*

*Faculty of Pharmacy, Musashino University, 1-1-20 Shin-machi, Nishitokyo-shi, Tokyo, Japan

Abstract

A highly diastereo- and enantioselective intramolecular 1,6-C–H insertion reaction of diaryldiazomethanes possessing an ether group has been achieved with the use of dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate] as a catalyst, providing exclusively 3-substituted cis-3,4-dihydro-4-phenyl-1H-isochromans in up to 99% ee with no evidence of tandem ylide formation–rearrangement.

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Published online: 15th February, 2021

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)60
Total Synthesis of (±)-4-Deoxyblennolide C via Spirochromanone

Takuya Kumamoto,* Sho Hasegawa, Kanna Adachi, and Kazuaki Katakawa

*Department of Synthetic Organic Chemistry, Graduate School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi Minami-ku, Hiroshima, 734-8553, Japan

Abstract

We report the total synthesis of (±)-4-deoxyblennolide C, a deoxy analogue of xanthone antibiotics blennolide C isolated from the fermentation broth of Blennoria sp. The synthesis involves construction of a quaternary carbon during the formation of spirochromanone through the aldol reaction of o-hydroxyacetophenones and cyclohexenone, oxidative cleavage of the alkene moiety, and the construction of a xanthone framework by Dieckmann condensation.

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Published online: 10th February, 2021

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)57
Chiral Phosphine Oxide-Catalyzed Enantioselective Ring Opening of Oxetanes

Shunsuke Kotani,* Yuka Tashima, Hiroki Tanaka, Shohei Aoki, and Makoto Nakajima*

*Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Chuo-ku, Kumamoto, Japan

Abstract

Chiral phosphine oxide as a Lewis base could effectively catalyze the enantioselective ring opening of 3-substituted oxetanes with silicon tetrachloride in the presence of N,N-diisopropylethylamine, affording the corresponding 2-substituted 1,3-chlorohydrins in high yields and good enantioselectivities.

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Published online: 10th February, 2021

Communication | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)65
Synthetic Studies on Didymeline Using Spirocyclization of Phenols with Diazo Functionality

Mitsuru Ikeda, Hiroki Nakayama, Ayaka Kanda, Shingo Harada,* and Tetsuhiro Nemoto*

*Pharmaceutical Chemistry, Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuo, Chiba, Japan

Abstract

Didymeline is an alkaloid with an azaspiro tricyclic skeleton with various functionalities. Despite the fact that its unique architecture is synthetically attractive, its total synthesis has never been achieved before. Herein, we present synthetic studies on the core structure of Didymeline. Accordingly, a spiro ring system was constructed through dearomatization of a phenol derivative with α-diazoamide unit. Based on the resulting 2-azaspiro[4,5]decane variant, a tricyclic molecule was synthesized via base-promoted intramolecular ring closure. For an asymmetric synthesis, an enantioselective dearomatization was also examined under silver catalysis, which led to the formation of an all-carbon substituted quaternary stereogenic center.

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Published online: 8th February, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)53
Divergent Total Synthesis of Azalamellarins D and N

Tsutomu Fukuda,* Seiya Okutani, Mayu Sumi, Kazuhito Miyagi, Gen Onodera, and Masanari Kimura

*Division of Chemistry and Materials Science, Graduate School of Engineering, Nagasaki University, 1-14, Bunkyo-machi, Nagasaki 852-8521, Japan

Abstract

Lamellarins are polycyclic marine alkaloids with potent cytotoxic activities against cancer cell lines. A divergent synthesis of azalamellarins D and N, lactam congeners of the marine natural products lamellarins D and N, has been achieved via the pentacyclic 14-bromo-8,9-dihydro-benzo[7,8]indolizino[3,2-c]- quinolin-6(5H)-one intermediate. The pentacyclic intermediate can be synthesized from methyl 1-(benzensulfonyl)-3-bromo-1H-pyrrole-2-carboxylate via the Suzuki–Miyaura cross-coupling and intramolecular direct arylation as key reactions.

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Published online: 8th February, 2021

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)46
Deprotection of the Carbazole PMB Group Using Hypervalent Iodine Reagent Combined with N-Hydroxyphthalimide

Kana Yoshikawa, Takanori Tabata, Kazuma Fujimura, Natsumi Kuraoka, Akira Nakamura, Yasuyoshi Miki, and Tomohiro Maegawa*

*School of Pharmaceutical Sciences, Kindai University, 3-4-1 Kowakae, Higashi-osaka, Osaka, 577-8502, Japan

Abstract

We developed a novel method for deprotecting the N-PMB group of carbazoles. The combination of PhI(OAc)2 and N-hydroxyphthalimide cleaved the N-PMB group with moderate to good yields depending on the substituents on the carbazole ring.

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Published online: 5th February, 2021

Communication | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)58
Planar Chiral [2.2]Paracyclophane-Based Bis(thiourea)-Catalyzed Highly Diastereo- and Enantioselective Michael Addition Reaction of Nitroethane to Nitrostyrenes

Shinji Kitagaki,* Eriko Shimo, Sawa Takeda, Rintaro Fukai, Naohiro Kojima, Shun Yoshioka, Naoko Takenaga, and Keisuke Yoshida

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

Abstract

To demonstrate the utility of [2.2]paracyclophane as a chiral organocatalyst backbone, we evaluated a planar chiral pseudo-ortho- [2.2]paracyclophane-based bis(thiourea) catalyst in the Michael addition reaction of nitroethane to nitrostyrenes. The catalyst produced the desired 1,3-dinitro compounds in high yields and high diastereo- and enantioselectivities.

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Published online: 1st February, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)62
Computational Study for the Aromatic Nucleophilic Substitution of 4-Dimethylamino-3-trifluoroacetyl- quinoline with Various Nucleophiles

Norio Ota, Souma Nakagawa, 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 aromatic nucleophilic substitutions of 4-dimethylamino- 3-trifluoroacetylquinoline 1 with amines, thiols, and alcohols are elucidated on the basis of DFT calculations. Our calculation results suggest that the reaction of 1 with amines giving N-N exchanged products 4 occurs via Meisenheimer type adducts V whereas the ones with thiols and alcohols proceed via the enol type adducts VII and IX to afford N-S and N-O exchanged products 8 and 9, respectively. It is also clarified that the conditions required for the successful substitution are not controlled by the activation energies on these processes, but by the energy changes on the processes from 1 to each intermediates, V, VII, and IX.

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Published online: 1st February, 2021

Communication | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)69
IBX Oxidations for the Synthesis of Substituted 2H-Pyrans

David R. Williams,* Seth A. Bawel, Nazanin Haddadpour, and Sarah Maier

*Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, IN 47405-7102, U.S.A.

Abstract

Facile oxidation of highly substituted 3,5-hexadien-1-ols using 3-iodoxybenzoic acid (IBX) in DMSO has resulted in a one-pot preparation of 2,3,4,6-tetrasubstituted 2H-pyrans. Cycloisomerizations of the 1-oxatriene moiety, produced in the oxidation, spontaneously occur via a disrotatory oxa-electrocyclization. The 2H-pyran products of Table 1 features three differentiated carbonyl substituents.

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Published online: 28th January, 2021

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)51
Total Synthesis of Urolithin C 3-Glucuronide

Katsunori Itaya, Ishtiaq Jeelani, and Hitoshi Abe*

*Department of Applied Chemistry, Faculty of Engineering, Toyama University, Gofuku 3190, Toyama 930-8555, Japan

Abstract

Urolithin is a metabolite of a class of compounds known as polyphenolswhich are found in various fruits, including pomegranates, nuts and strawberries. Urolithin is a biologically-active compound which has anti-inflammatory, antioxidant and anticancer properties. Our laboratory has focused on the use of a palladium-catalyzed intramolecular biaryl coupling reaction to yield urolithin C 3-glucuronide (uro-C 3-glur). The total synthesis of uro-C 3-glur has been accomplished in 11 steps starting from the commercially-available 3,4-dimethoxybenzaldehyde. We now report full details of the total synthesis of urolithin C 3-glucuronide (1).

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Published online: 25th January, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)49
Stereoselective Synthesis of Diastereomeric Berberine Alkaloids, O-Methylcorytenchirine and Coralydine

Misaki Kirii, Junpei Matsuoka, Akari Miyawaki, Kiyoshi Tomioka, and Yasutomo Yamamoto*

*Faculty of Pharmaceutical Sciences, Department of Medicinal Chemistry, Doshisha Women’s College of Liberal Arts, Kodo, Kyotanabe, Kyoto 610-0395, Japan

Abstract

Racemic total synthesis of diastereomeric berberine alkaloids, O-methylcorytenchirine and coralydine, was achieved from the common isoquinoline intermediate of norlaudanosine. The relative stereochemistry of C8-C14 was successfully constructed by favorable axial attack of nucleophiles to the iminium of dihydroprotoberberines.

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Published online: 25th January, 2021

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)67
Synthesis of 1-Azaazulenes Using Ring-Opening Cyclization of Spirocyclopropane with Amine

Hisanori Nambu,* Yuta Onuki, Koga Yamazaki, and Takayuki Yakura

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

Abstract

Synthesis of 1-azaazulenes using ring-opening cyclization of spirocyclopropane with a primary amine was accomplished. The reaction of cycloheptane-1,3-dione-2-spirocyclopropane with 2,4-dimethoxybenzylamine in refluxing acetonitrile resulted in a 94% yield of 1,2,3,6,7,8- hexahydrocyclohepta[b]pyrrol-4(5H)-one. The obtained product was successfully converted into 1-azaazulenes by deprotecting the amino-protecting group followed by oxidation.

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Published online: 22nd January, 2021

Review | Special issue | Prepress
DOI: 10.3987/REV-20-SR(K)7
Conformational Control in Stereoselective Chemical Reactions: From Amino Acids to Iminosugars

Ari Koskinen*

*Department of Chemistry and Material Sciences, Aalto University, Finland

Abstract

Two alternative synthetic strategies for the synthesis of vicinal amino alcohols from naturally occurring amino acids have been investigated, viz. one going through diastereoselective addition of organometallic species to an amino aldehyde and one going through α’-chiral α,β-enones and their diastereoselective reduction. Based on these investigations we were able to develop a synthetic strategy towards all diastereomers of deoxynojirimycin starting from naturally occurring serine through a divergent route with a late stage intermediate that can be prepared in large quantities and in enantiomerically pure form.

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Published online: 19th January, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-20-S(K)47
N-Glycosylation of Thio-glycoside Derived from Odorless Thiols Using Hypervalent Iodine(III) Reagent

Koji Morimoto, Kana Yanase, Tohru Kamitanaka, and Tetsuya Kajimoto*

*School of Pharmacy, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga, Japan

Abstract

A general and efficient protocol for direct N-glycosylation using inexpensive and readily available thioglycosides prepared from an odorless sulfur source was established. The use of easily available reactants and the mild reaction conditions make this protocol feasible for practical applications.

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