HETEROCYCLES

■ Contents

■ Chemical Reactions of Furochromones, Visnagin and Khellin

Magdy A. Ibrahim, Al Shimaa Badran,* Nasser M. El-Gohary, and Noura A. Abdel-fatah

*Department of Chemistry, Faculty of Education, Ain Shams University, Roxy, 11711, Cairo, Egypt

Abstract

This review represents the chemical reactivity of the natural products visnagin and khellin towards various chemical reactions, as well as summarizes the chemical behavior of some related compounds obtained from the rupture of the furan and γ-pyrone rings. In addition, the chemical reactivity of 6-formylnorvisnagin and 6-formylnorkhellin was summarized towards a variety of nucleophilic reagents.

■ Stereoselective Aza-Henry Reaction of 3-Nitro-dihydro-2(1H)-quinolones with N-Boc-Aldimines under the Catalysis of Chiral Ammonium Betaines

Daisuke Uraguchi, Masahiro Torii, Kohsuke Kato, and Takashi Ooi*

*Institute of Transformative Bio-Molecules (WPI-ITbM) and Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Nagoya 464-8601, Japan

Abstract

A highly enantioselective aza-Henry reaction between 3-nitro-dihydro-2(1H)-quinolones and N-Boc-aldimines was developed by using a chiral ammonium betaine as a catalyst. This protocol provides a direct synthetic method for accessing hydroquinoline derivatives possessing a tetrasubstituted stereogenic center at the C3 position and casts light on the utility of the α-functionalization of dihydroquinolones.

■ Silver-Mediated Sulfenylation of Indoles and Benzimidazoles with Di(hetero)aryl Disulfides

Wen-Juan Wang and Xi-Cun Wang*

*Key Laboratory of Polymer Materials, College of Chemistry and Chemical Engineering, Northwest Normal University, Gansu 730070, China

Abstract

An efficient synthesis of novel sulfenylated N-heterocycles derivatives via AgNO3 mediated C–S coupling reaction has been developed. This reaction could be carried out under mild reaction conditions with straightforward operation and good yield. A wide range of substrates can be utilized for the C–S coupling reaction giving sulfenylated indoles and benzimidazoles, which are the importance of frameworks in medicinal and synthetic chemistry.

■ Development of New Ligands for the Recyclable Catalytic Asymmetric Transfer Hydrogenation in Ionic Liquid

Hitomi Uchimoto, Miki Ikeda, Aoi Matsushita, Takashi Shigeta, Kenji Arimitsu, Hiroyuki Yasui, Tomoko Tsuji, Minoru Ozeki, Masayuki Yamashita, Kiyoharu Nishide, and Ikuo Kawasaki*

*School of Pharmaceutical Sciences, Mukogawa Women's University, 11-68 Koshien Kyuban-cho, Nishinomiya 663-8179, Japan

Abstract

The new ligands with improved enantioselectivity, recyclable catalytic asymmetric transfer hydrogenation (RCATH) reaction efficiency, and physical properties were synthesized. The new ligands were synthesized and used in RCATH. Among them, ligands 2e and 2f provided high enantioselectivity and reaction efficiency compared to a previously reported ligand 1 used in RCATH.

■ A Novel Tetrairidoid Glucoside from Pterocephalus hookeri

Shuai Huang, Jifa Zhang, Lianhai Shan, Yi Zhang,* and Xianli Zhou*

*School of Life Science and Engineering, Southwest Jiaotong University, Chengdu 610031, China

Abstract

Pterocephanoside (1), a novel iridoid glucoside derivative with three glucosides and an aromatic ring, were isolated from Pterocephalus hookeri, along with eight known compounds (2–9). The structure of the new compound was elucidated on the basis of extensive spectroscopic analysis, including 1D and 2D NMR experiments. Compounds 1, 2, 5 and 6 were evaluated for their cytotoxicity.

■ An Intramolecular Nucleophile-Catalyzed Aldol-Lactonization (NCAL) Reaction of S-Aryl-(E)-6-oxohex-2-enethioate with N,N-4-Dimethylaminopyridine N-Oxide

Hiroki Mandai,* Keita Shimowaki, Kohei Hongo, Koichi Mitsudo, and Seiji Suga*

*Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan

Abstract

We have developed an intramolecular nucleophile-catalyzed aldol-lactonization (NCAL) reaction of S-aryl-(E)-6-oxohex-2-enethiolate with N,N-4-dimethylaminopyridine N-oxide (DMAPO) to afford densely functionalized bicyclic β-lactones in moderate yield. This unique transformation may be explained in terms of nucleophilic substitution of the S-aryl moiety by DMAPO, followed by 1,4-addition of aryl thiolate to generate a zwitterionic enolate and an intramolecular C–C bond-forming reaction (aldol-lactonization).

■ Synthesis of 6,7-Dihydro-9,10-dimethoxydibenzo[a,f]quinolizinium Salt and Its D-Ring Substituted Derivatives

Kazuo Yamazaki, Mai Aritake, Shungo Takamoto, Midori Tabata, Sachiko Yanagihara, Keisuke Uji, Kazuaki Ohyama, Kei Ogiso, Takumi Sugahara, Ai Tatara, Tetsuji Hosono, Keitaro Suzuki, and Masashi Ohba*

*Yokohama University of Pharmacy, Matano-cho, Totsuka-ku, Yokohama 245-0066, Japan

Abstract

Synthesis of 6,7-dihydro-9,10-dimethoxydibenzo[a,f]quinolizinium salt (2a) and its derivatives (2b–g) substituted at the D ring has been achieved from 3-(2-bromoaryl)propanoic acid (3) in four steps for future examination of the inhibitory activity of these compounds against topoisomerase. The dihydrocarbostyrils (5a–g), key intermediates in this synthetic scheme, were prepared from the amides (4a–g) via intramolecular aryl amidation reactions.

■ A New Carbazole-Based Fluorescence Sensor for High Selective Detection of Copper(II) in Aqueous Solutions

Zhao Fang, Hu Yang, Li Qiao, and Hu Shengli*

*Hubei Collaborative Innovation Center for Rare Metal Chemistry, Hubei Key Laboratory of Pollutant Analysis & Reuse Technology, College of Chemistry and Chemical Engineering, Hubei Normal University, Huangshi 435002, China

Abstract

A new fluorescent sensor based on 9-ethylcarbazol and di-2-picolylamine was designed and synthesized. Its structure was confirmed by IR, NMR, MS spectra and elemental analyses. Its binding properties investigated by fluorescence spectroscope showed that it can selectively bind Cu2+ in anquous solution with fluorescence quenching.

■ Novel O-Benzyl Oxime Ethers of 1-(Thiophen-2-yl)ethan-1-one – Synthesis, Structure and Antimicrobial Activity

Tomasz Kosmalski,* Jolanta Kutkowska, Izabela Dwojak, Renata Studzińska, Adam Sikora, Bożena Modzelewska-Banachiewicz, and Andrzej Gzella

*Department of Organic Chemistry, Collegium Medicum, Nicolaus Copernicus University, Jurasza 2, 85-089 Bydgoszcz, Poland

Abstract

In this study, new O-benzyl oxime ethers of (2-thienyl)ethan-1-one were synthesized and tested for their antimicrobial activity. First, we prepared, in a pure form, (E)-oxime of (2-thienyl)ethan-1-one. Then, we obtained eight final products with good yields and purities. The structure elucidation of the titled compounds was performed by 1H NMR, 13C NMR and mass spectrum. X-Ray analysis was carried out to the compound 7. The compounds were tested to its antimicrobial activities against C. albicans, S. aureus, and E. coli.

■ An Efficient and Multi-Component Synthesis of Functionalized Pyrazole Derivatives

Juxian Wang, Juanjuan Zhang, Yue Zhao, Guoning Zhang, Yucheng Wang,* and Daqing Shi*

*College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, Jiangsu, China

Abstract

A facile and efficient one-pot procedure for the synthesis of functionalized pyrazole derivatives via a four-component reaction of malononitrile, ethyl cyanoacetate, hydrazine hydrate and aldehydes under mild conditions in excellent yield is described. This synthesis was confirmed to follow the group-assisted-purification (GAP) chemistry process, which can avoid traditional recrystallization and chromatography purifications.

■ Catalytic Asymmetric Intramolecular Cyclopropanation of α-Diazo-α-phosphoryl Acetate

Saori Inoue, Kotaro Nagatani, Yunosuke Hoshino, Haruka Tezuka, and Masahisa Nakada*

*Department of Chemistry and Biochemistry, Faculty of Science and Engineering, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555, Japan

Abstract

The catalytic asymmetric intramolecular cyclopropanation (CAIMCP) of α-diazo-α-diphenylphosphoryl acetate has been investigated. The maximum ee of the CAIMCP was 91% and the absolute configuration of the two products was successfully determined. Our previously reported model to explain the enantiofacial selectivity of the reacting alkene was successfully applied to rationalize the enantioselectivity of the CAIMCP.

■ An Improved and Economical Process for Preparation of Pregabalin, an Anticonvulsant

Fei Xiong,* Bin Yang,* Wei-Xiang Wang, Yue-Feng Zhao, Qing-Gang Tan, Shang-Wu Gu, Jia-Min Huo, Yao Xie, Jun-Zhe Yan, Xi-Lin Feng, and Ju Li

*Department of Chemistry, Fudan University, Shanghai 200043, China

Abstract

An improved, practical, economical and efficient process for the preparation of highly enantiomerically pure pregabalin (1) involving chemical resolution through diastereomeric crystallization is described herein. 3-Isobutylpentanedioic acid (2) is subjected to dehydration to afford 3-isobutylglutaric anhydride (3), followed by a ring-opening esterification with cinnamyl alcohol to form the racemic hemiester rac-4, which is, in turn, salified with an inexpensive organic base (1S,2S)-2-amino-1-(p-nitrophenyl)propane-1,3-diol (CHA) to form diastereomeric salts mixture. Then subsequently chemical resolution through diastereomeric crystallization to produce the desired enantiopure hemiester 4, which is the key chiral synthetic intermediate of pregabalin (1).