HETEROCYCLES

■ Contents

■ Chemistry and Biological Activities of Vibsane-Type Diterpenoids

Yoshiyasu Fukuyama,* Miwa Kubo, Tomoyuki Esumi, Kenichi Harada, and Hideaki Hioki

*Faculty of Pharmaceutical Sciences, Tokushima Bunri University, 180 Nishihamabouji, Yamashiro-machi, Tokushima, 770-8514, Japan

Abstract

This review focuses on the structural diversity, biological activities and synthesis of vibsane-type diterpenoids. Vibsane-type diterpenoids are considered to be rarely occurring natural products because they have been found exclusively in a few Viburnum species such as V. awabuki, V. odoratissimum, and V. suspensum. These diterpenoids are further classified into 11-membered ring, 7-membered ring, and rearranged (neovibsanin) types, and therefore, their chemical diversity forms a unique chemical library. We describe the absolute stereochemistry of the typical 11-membered ring vibsanins B and F, a variety of vibsane-type diterpenoids, the chemical correlations between the three subtypes, their biological activities, and the synthesis of vibsanin F and neovibsanin B.

■ Synthesis of Nitrogen- and Oxygen-Bridged Seven- to Ten-Membered Carbocycles Using Metathesis Reactions

Ken-ichi Takao* and Kin-ichi Tadano*

*Department of Applied Chemistry, Faculty of Science and Technology, Keio University, Hiyoshi, Kohoku-ku Yokohama 223-8522, Japan

Abstract

This review describes the synthesis of nitrogen- and oxygen-bridged seven- to ten-membered carbocycles using metathesis reactions and their applications to natural products synthesis achieved in the past decade.

■ Synthesis and Structure of 5,7-Dimethylthieno[3,4-d]pyridazine

Nathan C. Tice,* Sarah M. Peak, and Sean Parkin

*Department of Chemistry, Eastern Kentucky University, Richmond, KY, 40475-3102, U.S.A.

Abstract

The reaction of 2,5-dimethylthiophene-3,4-dicarboxaldehye (3) with excess hydrazine hydrate afforded the desired 5,6-fused ring thiophene derivative, 5,7-dimethylthieno[3,4-d]pyridazine (4), in high yield (82%). Pyridazine 4 was characterized spectroscopically and its structure was confirmed by X-ray crystallography. Compound 4 was observed to have an inverted, coplanar stacking arrangement in the solid state.

■ Synthesis of Some Novel Benzobisthiazoles

Oscene V. Barrett, Nadale K. Downer-Riley, and Yvette A. Jackson*

*Department of Chemistry, Mona Campus, University of the West Indies, Mona, Kingston 7, Jamaica

Abstract

The synthesis of angular and linear benzobisthiazoles via reaction of o-methoxythiobenzanilides with AIBN and basic ferricyanide is described.

■ Microwave-Assisted Selective Synthesis of 2H-Indazoles via Double Sonogashira Coupling of 3,4-Diiodopyrazoles and Bergman–Masamune Cycloaromatization

Hayato Ichikawa,* Haruhiko Ohfune, and Yoshihide Usami

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

Abstract

The microwave-assisted double Sonogashira coupling of 3,4-diiodo-1-trityl and 1-phenylpyrazole with terminal acetylene took only three minutes. Dialkynylpyrazoles, the coupling products, were heated at 240 °C in the presence of 1,4-cyclohexadiene to obtain 2H-2-trityl and 2-phenylindazoles, respectively. This synthetic route to 2H-indazole, which was achieved via cyclization to form the 6-membered ring of dialkynylpyrazole, is a novel procedure.

■ Synthesis, Structure and Electrochemical Behavior of a Novel Redox-Active Thiacalix[4]arene-Tetrathiafulvalene Assembly

Bang-Tun Zhao,* Wen-Bo Guo, and Pu-Zhou Hu

*No. 71, Longmen Road, Department of Chemistry, Luoyang Normal University, Luoyang 471022, Henan Province, China

Abstract

A novel redox-active thiacalix[4]arene-tetrathiafulvalene assembly 5 was carried out through triethyl phosphite-mediated cross-coupling of the corresponding two 1,3-dithiole-2-(thi)ones (3 and 4). The structure of thiacalix[4]arene-tetrathiafulvalene assembly 5 was identified by X-ray diffraction analysis. Meanwhile, the preliminary electrochemical properties of 5 was investigated by cyclic voltammetry (CV) and two one-electron quasi-reversible waves with redox potentials are observed.

■ Asymmetric 1,3-Dipolar Cycloaddition Reactions of Azomethine Imines with Acrolein Catalyzed by L-Proline and Its Derivatives

Hiroyuki Suga,* Tadashi Arikawa, Kennosuke Itoh, Yukihisa Okumura, Akikazu Kakehi, and Motoo Shiro

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

Abstract

1,3-Dipolar cycloadditions between acrolein and various N,N’-cyclic azomethine imines in the presence of L-proline and its derivatives as organocatalysts were investigated. Reactions that were catalyzed by (S)-indline-2-carboxylic acid (30 mol%) in CHCl3/MeOH 97:3 (v/v) showed high exo-selectivities (exo/endo 91:9 ~ 99:1) and enantioselectivities (75 ~ 98% ee). In contrast, reactions catalyzed by L-proline (30 mol%) under similar conditions favored the endo-cycloadduct (83:27 ~ 99:1) with modest to good enantioselectivities (31 ~ 83% ee). Based on our studies, the diastereoselective mechanism of the L-proline-catalyzed reaction was found to involve the isomerization of the exo- to the endo-cycloadduct in the presence of L-proline.

■ First Synthesis of 2-Tropolonylquinoline-4-carboxylic Acid Derivatives via Pfitzinger Reaction in Water

Wentao Gao,* Xiaofei Zhang, Yang Li, Huaye Liu, and Kimiaki Imafuku

*Institute of Superfine Chemicals, School of Chemistry and Chemical Engineering, Bohai University, 19 Keji Road, Jinzhou 121000, China

Abstract

A facile and clean synthesis of novel 2-tropolonyl substituted quinoline-4-carboxylic acids via Pfitzinger reaction of 3-acetyltropolone or 3-acetyl-5-bromotropolone with different isatins in water was described. It was the first time that the Pfitzinger reaction was applied to the troponoid field. The structures of all the synthesized compounds were characterized by elemental analysis and spectral data.

■ Improved Total Synthesis of Racemic Rutamarin

Ling Tong, Ruisheng Xiong, Hong Jiang, Xiangrui Jiang,* Hongbin Sun,* Hualiang Jiang, and Jingshan Shen

*Chinese Academy of Sciences, Shanghai Institute of Materia Medica, 555 Zuchongzhi Rd., Zhangjiang Hi-Tech Park, Shanghai, 201203, China

Abstract

An improved, convenient and cost-effective process, using 2,4-dihydroxybenzaldehyde 2 as starting material for (±)-rutamarin 1, is described. The overall yield of 1 is 44% in eight steps, requiring no chromatographic purification.

■ Synthesis of 3-Substituted Benzo[b]thiophenes via the Reaction of α-Substituted 2-Lithio-β-methoxystyrenes with Sulfur

Kazuhiro Kobayashi,* Daisuke Nakai, Shuhei Fukamachi, and Hisatoshi Konishi

*Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, 4-101 Koyama-minami, Tottori 680-8552, Japan

Abstract

3-Substitued benzo[b]thiophenes were synthesized in reasonable overall yields from α-substituted 2-bromo-β-methoxystyrenes. Thus, the bromine-lithium exchange between these bromostyrenes with butyllithium in diethyl ether at 0 ˚C followed by reaction with sulfur afforded the corresponding α-substituted β-methoxy-2-sulfanylstyrenes. These were then treated with an equimolar amount of concentrated hydriodic acid in acetonitrile at room temperature to give the desired products.

■ Synthesis of Galacto- and Mannosucroses

Atsushi Ueda, Takanori Yamashita, and Jun'ichi Uenishi*

*Kyoto Pharmaceutical University, Misasagi, Yamashina-ku, Kyoto 607-8412, Japan

Abstract

A concise synthesis of β-D-fructofuranosyl α-D-galactopyranoside (2), and β-D-fructofuranosyl α-D-mannopyranoside (3) is described. Inversion of the C-3 α-hydroxy group of α-D-galactopyranosyl and α-D-mannopyranosyl β-D-psicofuranosides 10 and 11 via oxidation and stereoselective reduction furnished the corresponding β-D-fructofuranosides in excellent yields.