Special Issue

Yasuyuki Kita's Special Issues, Vol. 103, No. 2, 2021

42 data found. 31 - 42 listedFirst Previous
Paper | Special issue | Vol 103, No. 2, 2021, pp. 980 - 994
Published online: 23rd March, 2021
DOI: 10.3987/COM-20-S(K)72
Claisen Rearrangement of 4-Allyloxy-1-p-methoxy 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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Paper | Special issue | Vol 103, No. 2, 2021, pp. 995 - 1010
Published online: 26th March, 2021
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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Short Paper | Special issue | Vol 103, No. 2, 2021, pp. 1011 - 1022
Published online: 18th December, 2020
DOI: 10.3987/COM-20-S(K)42
Catalytic Asymmetric Ring-Opening of σ-Symmetric Cyclic Carbonates with Chiral Amino Sulfonamide Catalysts

Michiyasu Nakao, Tomomi Shozui, Daisuke Inoue, Takahito Ihara, Syuji Kitaike, and Shigeki Sano*

*Graduate School of Pharmaceutical Sciences, Tokushima University, 1-78 Sho-machi, Tokushima 770-8505, Japan

Abstract

Enantioselective ring-opening of σ-symmetric six-membered cyclic carbonates with benzyl alcohol catalyzed by 20 mol% of chiral amino sulfonamide catalysts afforded chiral acyclic carbonates in up to 79% ee.

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Short Paper | Special issue | Vol 103, No. 2, 2021, pp. 1023 - 1030
Published online: 10th December, 2020
DOI: 10.3987/COM-20-S(K)44
An Arylative Aziridination Process toward Aspidosperma Alkaloids

Kouassi Signo, Elsa Deruer, Siomenan Coulibali, and Sylvain Canesi*

*Laboratoire de Méthodologie et Synthèse de Produits Naturels, Université du Québec à Montréal, C.P. 8888, Succ. Centre-Ville, Montréal, H3C 3P8, Québec, Canada.

Abstract

An arylative aziridination process has been developed from dibrominated phenols containing a Fukuyama sulfonamide on the lateral chain. A two-step procedure involving the formation of a dienone by a phenol oxidation reaction mediated by a hypervalent iodine reagent (Kita reaction) followed by an intramolecular arylative aziridination process was used. This second step occurred under mild conditions via a Michael–Smiles ring-closure cascade, producing sulfur dioxide as the only byproduct. Additionally, a stereoselective approach was observed with tyrosine derivatives. This transformation respects the rules of green chemistry and atom economy. These new polyfunctionalized scaffolds could offer several synthetic possibilities for the total synthesis of natural products such as the main core of Aspidosperma alkaloids.

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Short Paper | Special issue | Vol 103, No. 2, 2021, pp. 1031 - 1037
Published online: 8th February, 2021
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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Short Paper | Special issue | Vol 103, No. 2, 2021, pp. 1038 - 1047
Published online: 28th January, 2021
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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Short Paper | Special issue | Vol 103, No. 2, 2021, pp. 1048 - 1056
Published online: 10th February, 2021
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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Short Paper | Special issue | Vol 103, No. 2, 2021, pp. 1057 - 1063
Published online: 5th March, 2021
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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Short Paper | Special issue | Vol 103, No. 2, 2021, pp. 1064 - 1077
Published online: 15th February, 2021
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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Short Paper | Special issue | Vol 103, No. 2, 2021, pp. 1078 - 1098
Published online: 17th February, 2021
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, Musasino University, Shinmachi 1-1-20, Nishitokyo, 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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Short Paper | Special issue | Vol 103, No. 2, 2021, pp. 1099 - 1107
Published online: 25th January, 2021
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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Short Paper | Special issue | Vol 103, No. 2, 2021, pp. 1108 - 1115
Published online: 15th March, 2021
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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42 data found. 31 - 42 listedFirst Previous