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Special Issues

6 data found. 1 - 6 listed

Published online: 28th December, 2017

Communication | Special issue | Prepress
DOI: 10.3987/COM-17-S(T)7
Enantioselective Cycloadditions between Aliphatic Nitrile Oxides and 2-Hydroxystyrenes Catalyzed by Chiral Amine-Urea

Yasunori Toda, Masato Koyama, Hiroyoshi Esaki, Kazuaki Fukushima, and Hiroyuki Suga*

*Department of Materials Chemistry, Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan

Abstract

Chiral amine-urea-catalyzed enantioselective 1,3-dipolar cycloadditions of nitrile oxides with 2-hydroxy-3-methoxystyrene are described. Aliphatic aldehyde-derived hydroximoyl chlorides were used as nitrile oxide precursors, providing optically active isoxazolines with moderate to good enantioselectivities.

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Published online: 26th December, 2017

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-17-S(T)8
Stereoinversion of a Tertiary Alcohol on a THP Ring: a Recovery Route to an Intermediate for Gymnocin-A

Takeo Sakai, Kayo Aoyama, Rie Oshima, Kyoko Furukawa, and Yuji Mori*

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

Abstract

The stereoinversion of a tertiary alcohol on a tetrahydropyran ring was achieved through a five-step sequence including regioselective dehydration, diastereoselective epoxidation and reduction. This approach offers a recovery route from the diastereomer to the desired tertiary alcohol as part of the synthesis of gymnocin-A.

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Published online: 19th December, 2017

Short Paper | Special issue | Prepress
DOI: 10.3987/COM-17-S(T)6
Concise Approach to Mono- and Disubstituted Luotonin A Analogs and Their Cytotoxicity Test

Natsuko Kagawa,* Kimiko Nishimura, Shinya Abe, Takashi Masuko, and Masahiro Toyota*

*Department of Chemistry, Graduate School of Science, Osaka Prefecture University, 1-1 Gakuencho, Sakai, Osaka 599-8531, Japan

Abstract

A concise approach for the preparation of luotonin A analogs has been developed. The new synthetic route contains an anion-assisted intramolecular double hetero Diels ̶ Alder reaction and a direct oxidative cross coupling reaction. Some synthetic luotonin A analogs show cytotoxic activities against Daudi and Jurkat human cancer cells as potent as camptothecin.

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Published online: 18th December, 2017

Paper | Special issue | Prepress
DOI: 10.3987/COM-17-S(T)2
Synthesis of Substituted t-Butyl 3-Alkyl-oxindole-3-carboxylates from Di-t-Butyl (2-Nitrophenyl)malonates

Yusuke Yamai, Akio Tanaka, Tatsuo Yajima, 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

Using a novel tandem reduction-cyclization, we synthesized t-butyl 3-alkyloxindole-3-carboxylates from the di-t-butyl 2-alkyl-2-(2-nitrophenyl)-malonate. Introduction of an α-substituent to the di-t-butyl 2-(2-nitrophenyl)-malonates and addition of acid promoted reactivity. This methodology was successfully applied to gram-scale-synthesis of the t-butyl 3-methyloxindole-3-carboxylate 1 and 3-hydroxymethyl-3-methyloxindole 2 without silica gel column chromatography.

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Published online: 17th November, 2017

Paper | Special issue | Prepress
DOI: 10.3987/COM-17-S(T)1
Asymmetric Total Synthesis and Structure Confirmation of (+)-(3E)-Isolaurefucin Methyl Ether

Te-ik Sohn, Byungsook Kim, Deukjoon Kim,* and Robert S. Paton

*The Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Shillim-Dong, San 56-1, Kwanak-Gu, Seoul 151-742, Korea

Abstract

An asymmetric total synthesis and structure confirmation of (+)-(3E)-isolaurefucin methyl ether (2a) was accomplished. Our synthesis features two complementary routes to construct the α,α’-trans-2,8- dioxabicyclo[5.2.1]decane skeleton of the natural product from α,α’-trans-γ,δ-unsaturated oxocene alcohol 7, namely, an intramolecular epoxide opening route and a novel methoxyetherification route based on organoselenium- mediated oxonium ion formation/fragmentation. A computational analysis was performed to model the observed different fragmentation behaviors of the respective oxonium ions 8 and 8’ derived from α,α’-trans- and α,α’-cis-γ,δ-unsaturated oxocene alcohols 7 and 7’ during the organoselenium-mediated oxonium ion formation/fragmentation. Regarding the possibility of the natural product being an artifact, the reactivity of chlorofucin surrogate 16 and neoprelaurefucin surrogate 16’ during methanolysis was compared, the results were in good agreement with calculations.

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Published online: 17th November, 2017

Paper | Special issue | Prepress
DOI: 10.3987/COM-17-S(T)3
Polymeric Silver(I) Complexes Based on Bidentate Imidazoline-2-thiones Synthesis and Crystal Structures

Barbara Rietzler, Gerhard Laus, Klaus Wurst, Thomas Gelbrich, Sven Nerdinger,* Erwin Schreiner, and Herwig Schottenberger

*Sandoz GmbH, Biochemiestrasse 10, 6250 Kundl, Austria

Abstract

The bidentate ligand 1,6-bis(1-methylimidazol-2-ylthio)hexane or its hexafluoride salt reacted with silver(I) triflate, nitrate or oxide, respectively, to give the corresponding polymeric silver(I) complexes. Three crystal structures have been determined and showed linear and cyclic motifs.

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6 data found. 1 - 6 listed