The demand for functionalized aromatic compounds is growing rapidly in many research fields. Therefore, the efficient synthesis of desired aromatic compounds is a critical issue in organic synthesis. In this account, we describe new synthetic approaches to versatile aromatic compounds, such as phenols, benzenes, 3-hydroxypyridines, and styrenes, by ring-closing olefin metathesis (RCM)/aromatization and ring-closing enyne metathesis (RCEM)/aromatization of acyclic precursors. The advantages in terms of simplicity, flexibility, and avoidance of the formation of regioisomers are proof of the versatility of this method for the synthesis of aromatic compounds.
In this review, the results of studies on new methodology for bond activation by using transition metal complexes are described, in order to realize the expeditious and selective synthesis of organic compounds. Carbon-carbon bond formation reactions, accompanying with cleavage of unactivated bonds such as carbon-carbon, carbon-boron, and carbon-silicon bonds, are reported. This review involves, for examples, the new synthetic methodology to introduce both cyano and ester groups (cyanoesterification) via the C-C bond activation, regio- and stereoselective synthesis multi-substituted olefins mediated a zirconocene complex via the C-B bond activation, and cross-coupling reaction of alkynylsilanes activated by a copper salt via the C-Si bond cleavage. Each reaction can be applicable to synthesis of functional molecules such as opto-electronic materials, an anti-cancer agent, and liquid crystalline compounds.
Calixarenes constitute an important class of macrocyclic compounds in both fundamental research and application as a result of the versatile functions as a host molecule. In recent years, a variety of calixarene analogues involving heteroatoms as the bridging units have been reported because the replacement of the methylene bridges of calixarenes with heteroatoms can impart novel properties and functions to molecules. Of them, nitrogen-bridged calixarene analogues, simply called as “azacalixarenes”, have recently emerged as a new calixarene family. The diversity is limited yet, but interesting structure-property relationships based on the introduction of nitrogen atoms as the bridging units have thus far been disclosed. This review summarizes the current developments of the syntheses, complexation abilities, and oxidation behaviors of azacalixarenes.
Otteliones A and B, isolated from the fleshwater plant Ottelia alismoides, were found to exhibit extremely potent growth-inhibitory activity against human cancer cell lines. Structurally, these small-molecule natural products possess a novel bicyclic hydrindane skeleton with four contiguous asymmetric carbon centers, in which the rare and sensitive 4-methylene-2-cyclohexenone substructure is a special characteristic feature. When these natural products were isolated, the relative configuration of ottelione B was determined; however, ottelione A could not been assigned unambiguously. In this article, we describe the first enantioselective total synthesis of (+)-ottelione A, (-)-ottelione B, and (+)-3-epi-ottelione A (the earlier proposed stereostructure of ottelione A) using a flexible synthetic scheme that allows an access to all possible stereostructures of ottelione A. The present total synthesis has fully established the absolute configuration of these natural products. In addition, the cell growth inhibition analysis and tubulin polymerization assay of the synthesized otteliones are also described.
Organic carbonates such as dimethyl carbonate (DMC) and ethylene carbonate (EC) are useful intermediates for manufacturing polycarbonates through a non-phosgene process. In addition, organic carbonates are employed as electrolyte solvents in lithium ion batteries and are widely used as aprotic polar solvents. We wish to report our recent works concerning new synthetic procedures for linear and cyclic organic carbonates starting from carbon dioxide. The first methodology is dehydrative condensation of methanol with carbon dioxide. The keys for obtaining high conversion and selectivities are a) development of easily recyclable dehydrating agents; i.e. dimethyl acetals and b) addition of a small amount of acid cocatalysts; i.e. Ph2NH2(OTf). The second methodology is the cyclization of the oxiranes with carbon dioxide resulting in cyclic carbonates. The cyclization is thermodynamically favorable and continuous flow processes are demonstrated based on immobilized catalysts.
We synthesized various block-like molecules based on stereochemistry of tertiary aromatic amide which prefers cis (folded) conformation and weak intramolecular interactions such as aromatic-aromatic interactions. Their crystal structures and dynamic behaviors in solution were revealed by X-ray crystallographic analysis and dynamic 1H NMR measurement. The block-like molecules were triangular, rhombic, twisted, spherical or pinched circle in shape. Some of them aggregated into a channel-shaped network via weak intermolecular interactions.
Cyclic polymers can be effectively synthesized by ring-expansion polymerization, which does not cause random catenation even under undiluted conditions. This mini review focuses on recently developed controlled ring-expansion polymerizations.
Recent advances in synthetic studies on steroidal alkaloid, (+)-cortistatin A, are described. (+)-Cortistatin A shows a potent and selective anti-angiogenetic activity against human umbilical vein endothelial cells (HUVECs) at nM concentrations and expected as a novel anticancer drug candidate. (+)-Cortistatin A has attracted considerable attention of not only biologists but also synthetic chemists because of its unique highly functionalized abeo-9(10,19)-androstane structure and potent biological activity. Thus the total syntheses of (+)-cortistatin A have been reported by three groups and the synthetic studies are currently underway by several groups. This review focuses on synthetic approaches taking advantage of using steroidal derivatives through ring expansion reaction to construct the core structure of (+)-cortistatin A reported by Corey and Baran respectively.
An extracelluler matrix is collapsed and a cell is revealed by hyaluronidase resolving hyaluronic acid. As this result, a pathogen, an inflammation mediation material, and various kinds of medicines such as an inflammation agent or a preservative will damage the revealed cell. Therefore it is expected that hyaluronidase inhibitor causes antiinflammation and anagenesis. It is known that a lot of sulfated polysaccharides have hyaluronidase inhibition activity. We focused cellulose sodium sulfate, which is a kind of sulfated polysaccharides, and evaluated the hyaluronidase inhibition activity of cellulose sodium sulfate. Then, we investigated the close relation with a skin and cellulose sodium sulfate. We confirmed that cellulose sodium sulfate has superior hyaluronidase inhibition ability, and is a promising material having the superior moisture retention characteristics.