Structure-activity relationships of phomactin derivatives as platelet activating factor antagonists

Phomactins, natural products isolated from the culture broth of marine fungus Phoma sp., were found to be active as PAF antagonists. This unique carbon skeleton led us to investigate the structure-activity relationship demonstrating that the lipophilicity at C-(7-8), acetoxy, (methoxycarbonyl)oxy, and 3-isoxazolyloxy substitution at C-20, and 2-beta-OH configuration at C-2 are all required for the enhancement of inhibitor activity.     

A perspective on the contribution of surfactants and lipids toward “Green Chemistry”: Present states and future potential

“Green Chemistry” has become a subject of increasing interest in recent years. The goal of efforts in this area is to develop environmentally friendly methods and processes to replace traditional reactions that use organic solvents, consume much energy, and generate undesirable by-products and/or waste. Utilization of renewable resources is an important component of Green Chemistry. Fats and oils represent one such resource. They can give rise to many types of surfactants and lipids that can modify properties of boundary phases between different phases. Thus, phase-transfer catalysts (PTC) based on surfactants or lipids have been reported to be useful in reactions such as oxidation and hydration reactions and in glycidyl ether formation. Another approach to satisfying Green Chemistry requirements is the recovery and recycling of reactants and/or substrates used. In the preparation of alkyl glyceryl ethers, the intermediate 1,3-dioxolane compounds prepared by addition of acetone to alkyl glycidyl ethers can be hydrolyzed to regenerate reusable acetone. Other examples of methodologies based on surfactants or lipids are summarized, and their potential contribution to Green Chemistry is discussed.     

Applications of protecting groups in the synthesis of surfactants, lipids, and related compounds

Several types of alkyl ether lipids were prepared in high yield and high purity using protecting groups such as 1,3-dioxolane compounds or allyl ethers. We also succeeded in the industrial production of alkyl glyceryl ethers using the reaction of alkyl glycidyl ethers with acetone to give 1,3-dioxolane compounds, from which the desired alkyl glyceryl ethers were obtained in high quantities. 1,3-Dioxolane (ketal) compounds based on acetone were used in the enzymatic preparation of monoglyceride on an industrial scale. On the basis of these protecting groups, we extended our studies concerning both the preparations and properties of novel polyol ether compounds, beginning with alkyl glycidyl ethers. Another typical property of surfactants containing 1,3-dioxolane units and acetal is degradability under acidic conditions. Several types of destructible/cleavable surfactants based on polyols, such as carbohydrates and polyethyleneglycol, were prepared. As for natural products containing polyol skeletons, much attention has been paid to their molecular design, in which protecting groups such as 1,3-dioxolane compounds or allyl ether have contributed to synthetic strategies.     

Applications of phase-transfer catalytic reactions to fatty acids and their derivatives: Present state and future potential

Phase-transfer catalysts (PTC), which accelerate reactions between liquid(organic)-liquid(water) and liquidsolid heterogeneous states, have been investigated and developed. Several processes with PTC have succeeded in industrial processes involving fatty acids and their derivatives. For example, preparation of fatty alkyl glycidyl ethers, from which fatty alkyl glyceryl ethers and their derivatives can be obtained, has been carried out with PTC. However, some problems remain to be solved. For example, preparation of the fatty alkyl glycidyl ether by a PTC reaction was considered, but typical problems to be solved included: (i) how to reuse or recover the catalysts; (ii) how to control the heterogeneous reaction without obstacles to produce useful chemical materials; (iii) how to satisfy the environmental requirements for the catalysts; and (iv) are there more effective catalysts? We address these problems based on our own experiences with phase-transfer catalytic Williamson ether syntheses of fatty alkyl glycidyl ethers. Moreover, we describe recent developments in phase-transfer catalytic reactions related to oleochemistry, such as transition metal-catalyzed reactions of long-chain olefins in liquid(organic)-liquid(water) or liquid-solid heterogeneous states. Based on these results, we have considered the potential of PTC as a synthetic tool in oleochemistry.     

A case of herpes simplex encephalitis presenting complete destruction of the medial portions in the bilateral temporal lobes

A 57-year old man, who had suffered from herpes simplex encephalitis and had been cured without antiviral agents, was admitted to our hospital three years after the encephalitis. He had a complete loss of memory for events subsequent to the encephalitis and a retrograde amnesia for the several years leading up the encephalitis. MRI revealed the abnormalities located in the limbic system, especially the medial portions in the bilateral temporal lobes of the cerebrum were completely destroyed. We consider that this case suggests the specific affinity of herpes simplex virus especially for the medial portions in the temporal lobes of the cerebrum.     

B-90063, a novel endothelin converting enzyme inhibitor isolated from a new marine bacterium, Blastobacter sp. SANK 71894

We raised mAbs to whole L5178Y leukemia/lymphoma (LL) cells to identify adhesion proteins involved in adherence between LL cells and marrow stromal cells. One mAb, 4C, and its subclones 4C.1 and 4C.2 inhibited adherence of L5178Y LL cells to MLT. a nontransformed murine marrow stromal cell line. These MoAbs are directed against CD45RA. Control anti-CD45 mAbs and isotype mAbs were non-inhibitory. Other anti-CD45 mAbs, M1/9.3, RA3-3A1/6.1 and RA3-2C2/1 do not compete with mAb 4C.1 for binding to the L5178Y cell surface, but mAb 4C.1 competes for binding of mAb RA3-2C2/1. Effects of mAb 4C on tyrosine-phosphatase activity of CD45 in L5178Y cells are minimal, suggesting direct involvement of CD45 as an adhesion protein.     

Stress intensity factors of a central interface crack in a bonded finite plate and periodic interface cracks under arbitrary material combinations

Although a lot of interface crack problems were previously treated, few solutions are available under arbitrary material combinations. This paper deals with a central interface crack in a bonded finite plate and periodic interface cracks. Then, the effects of material combination and relative crack length on the stress intensity factors are discussed. A useful method to calculate the stress intensity factor of interface crack is presented with focusing on the stress at the crack tip calculated by the finite element method.     

Internal photoemission spectroscopy measurement of Alq3/cathode interface by three layered electron only device

We have investigated the Schottky barrier height for electrons at aluminum tris (8-hydroxyquinoline) (Alq₃)/cathode interfaces by internal photoemission (IPE) measurement. A three layered device consisting of ITO/TiO₂/intermediate layer (IL)/Alq₃/cathode structure was used to fabricate the “electron-only device” and to reduce the equivalent thickness of TiO₂ and IL stack. The measured barrier heights were 0.86, 1.05, 1.3 and 1.55 eV for MgAg, Al, Ag and Au electrodes, and it gradually decreased with external voltage and it was explained as Schottky effect. Barrier height showed linear relationship with work-function and electronegativity of cathode materials. The slope parameter of 0.6 with electronegativity was attributed to the interfacial charge transfer through the metal-induced gap states at the cathode/Alq₃ interface.     

Newer synthetic approaches to surfactants, lipids, and related compounds based on C-3 building blocks: Recent advances related to fatty chemistry

Many lipids derived from natural sources are based on the glycerin molecule. Synthetically alkyl glycidyl ether can be used as a C-3 building block for lipid molecules as well as alkyl glyceryl ether. Several glycidyl and glyceryl ethers have been studied as C-3 synthetic building blocks for lipids used in surfactants/emulsifiers, cosmetics, or toiletries. From an environmental viewpoint, several surfactants and detergents have been modified by using epichlorohydrin or glycerides as C-3 building blocks to have higher performance or biodegradability. Recently, complex lipid molecules having special bioactivities have attracted attention among chemists. Glycidyl ether would be expected to be one of the synthetic building blocks for such complex lipids.