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Published online: 17th August, 2021

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-21-S(R)4
Isolation of Ikahonone, 4-methyl-2,4-dihydroxy-3-pentanone from Bacillus cereus IFM12235

Yasumasa Hara, Mareno Chiba, Keiichiro Watanabe, and Masami Ishibashi*

*Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8675, Japan

Abstract

A new ketone, ikahonone (1), and five known compounds (2-6) were isolated from Bacillus cereus IFM12235 collected in Japan. The structure of compound 1 was elucidated using spectral studies, including NMR. The absolute configurations of 1 and 2 were determined by comparing electronic circular dichroism (ECD) spectra with known compounds and calculating the ECD spectra of 1 and 2. Three compounds (2-4) were previously prepared by synthesis, and first isolated as natural products in the present study.

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Published online: 11th August, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-21-S(R)5
Azuleno[6,5-b]indoles: Palladium-Catalyzed Oxidative Ring-Closing Reaction of 6-(Arylamino)azulenes

Taku Shoji,* Yukino Ariga, Shunji Ito, and Masafumi Yasunami

*Department of Science, Graduate School of Science and Technology, Shinshu University, Matsumoto 390-8621, Nagano, Japan

Abstract

6-Bromoazulene derivative with two n-butoxycarbonyl groups was prepared by the modification procedure of Nozoe’s azulene synthesis. The aromatic nucleophilic substitution reaction of the 6-bromoazulene derivatives having two-ester functions with aniline derivatives proceeded to give the corresponding 6-(arylamino)azulene derivatives. Palladium-catalyzed oxidative ring-closing reaction of the 6-(arylamino)azulene derivatives provided the azuleno[6,5-b]indoles in moderate to good yields.

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Published online: 22nd June, 2021

Communication | Special issue | Prepress
DOI: 10.3987/COM-21-S(R)3
Synthesis and Optical Properties of Azuleno[1,2-b]benzothiophene and Selenophene

Mio Matsumura,* Taiki Kamiya, Masato Kawakubo, Yukako Hayashi, Tadashi Hyodo, Yuki Murata, Kentaro Yamaguchi, and Shuji Yasuike*

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

Abstract

Benzothiophene- and benzoselenophene-fused azulene derivatives were synthesized by Cu-catalyzed tandem cyclization via the Ullmann-type S/Se– arylation and Csp2–H chalcogenation of 2-(2′-bromophenyl)azulene. The maximum absorption of tetracyclic products was red-shifted from that of 2-phenylazulene, which does not contain a bridged chalcogen atom. Single-crystal X-ray analysis of azuleno[1,2-b]benzoselenophene revealed that the benzo[b]selenophene and azulene rings are almost coplanar.

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Published online: 22nd June, 2021

Review | Regular issue | Prepress
DOI: 10.3987/REV-21-964
Synthesis of Multisubstituted Benzofurans/Indoles Using Multichlorinated Phenols/Anilines via Palladium-Catalyzed Site-Selective Sonogashira Coupling

Miyuki Yamaguchi and Kei Manabe*

*School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga, Shizuoka 422-8526, Japan

Abstract

Multisubstituted benzofurans/indoles are a critical class of compounds in the fields of pharmaceuticals and natural products. A useful method of preparing 2-substituted benzofurans/indoles is the Pd-catalyzed Sonogashira coupling of 2-halophenols/2-haloanilines and terminal alkynes, followed by cyclization. For the syntheses of multisubstituted benzofurans/indoles, the use of multichlorinated phenols/anilines as coupling partners is powerful because the synthetic steps required are reduced and all dichlorophenol and dichloroaniline positional isomers are commercially available and inexpensive. However, their use in benzofuran/indole synthesis is limited because of their low reactivity compared with those of the corresponding iodo or bromo compounds. Furthermore, site-selective Sonogashira coupling at the 2-position of the multihalogenated phenols/anilines is sterically and electronically challenging. To overcome these problems, dihydroxyterphenylphosphine (DHTP) has been developed as a ligand that enables the highly ortho-selective Sonogashira coupling of 2-chlorophenols/2-chloroanilines with terminal alkynes. Using the Pd–DHTP catalyst, chlorinated benzofurans/indoles are successfully obtained, which are easily converted to other derivatives by substitution of the chloro group. In this review, we summarize this and related studies to demonstrate the utility of this method.

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Published online: 1st June, 2021

Paper | Special issue | Prepress
DOI: 10.3987/COM-21-S(R)2
New Sugar Based γ-Amino Silyl Ether Organocatalysts for Asymmetric Michael Addition of β-Keto Esters with Nitroolefins

Divakar Ganesan, Perumalsamy Parasuraman, Zubeda Begum, Rajkumar Thiyagarajan, Chigusa Seki, Yuko Okuyama, Eunsang Kwon, Koji Uwai, Michio Tokiwa, Suguru Tokiwa, Mitsuhiro Takeshita, and Hiroto Nakano*

*Graduate School of Engineering, Muroran Institute of Technology, 27-1 Mizumoto-cho, Muroran 050-8585

Abstract

New sugar based γ-amino silyl ether organocatalysts were synthesized and their catalytic ability was examined in asymmetric Michael addition of β-keto esters with nitroolefins affording chiral Michael adducts with quaternary carbon stereocenter in good to excellent chemical yields, diastereoselectivities and moderate enantioselectivities (up to 97%, up to dr. 85:15, up to 56% ee).

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Published online: 27th May, 2021

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-21-S(R)1
Lipase-Catalyzed Site-Selective Deacetylation of 2-Methoxy-3-methylnaphthalene-1,4-diol Diacetate for Construction of Characteristic Substituted 1,2,3,4-Tetrahydroisoquinoline Derivative of Novel Ecteinascidin Marine Natural Product

Masashi Yokoya,* Ryo Sato, and Naoki Saito

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

Abstract

We developed a site-selective deacetylation of 2-methoxy-3-methylnaphthalene-1,4-diol diacetate catalyzed by Candida antarctica lipase B, which furnished 1-hydroxy-2-methoxy-3-methylnaphthalen-4-yl acetate in 88% yield. This product was transformed into 2-methoxy-3-methylnaphthalen-1-ol in a five-step sequence (30.5% overall yield from 7a). It is a novel procedure for preparing a characteristic A ring substituted system for both safracin antibiotics (2) and ecteinascidin marine natural products (1).

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36 data found. 31 - 36 listedFirst Previous