This article reviews our approaches for designing fluorinated lipid liquid–crystal membranes suitable for biomaterials such as membrane protein reconstitution matrices. We proposed several partially fluorinated fatty acids as well as phospholipids bearing long (C18) hydrophobic chains comparable to biomembrane lipids. The fatty acids and/or phospholipids containing perfluoroalkyl group was easily synthesized in good yields. Judging from the collapse (equilibrium spreading) pressures of the proposed fatty aids and/or phospholipids at the air–water interface, the partial fluorination of hydrophobic chains was enough to improve their monolayer stability. The fluorinated phospholipid with C–C triple bonds formed flexible structures such as stable vesicles in water at a room temperature. The partially fluorinated phospholipids are applicable to protein reconstitution matrices, e.g., reconstitution of photosynthetic membrane proteins.
The translation machinery is generally designated to synthesize polypeptides consisting of 20 proteinogenic (natural) amino acids. Significantly, the ribosomal synthesis is employed in mRNA–template dependent manner, i.e. the sequence of mRNA dictates that of polypeptide according to the genetic code, enabling us to design the peptide sequence by simply preparing the corresponding mRNA or its DNA as the template for transcription. From the synthetic point of view, however, the fact that the useable monomers are limited to 20 proteinogenic amino acids is a serious restriction for the preparation of peptide library with high chemical diversities. In this review, we shall discuss an emerging new technology, referred to as genetic code reprogramming, that allows us to express natural product–like non–standard peptides using a reconstituted cell–free translation system. This technology will open a new avenue for the discovery of a new class of non–standard peptides.
Oxidative cleavage of carbon–carbon double bonds to carbonyl compounds is an essential operation in organic synthesis. Ozonolysis is generally accepted as the standard method for this direct transformation. However, its utility is often limited by safety concerns. Use of high–valent oxometals such as RuO4, OsO4, and MeReO3 in combination with a number of oxygen donors as stoichiometric oxidants is suitable for the oxidative catalytic cleavage of olefins, but they are expensive and/or toxic. Therefore, the development of a safe and environmentally friendly procedure for the cleavage of carbon–carbon double bonds is highly desirable. In this review, we report a safe, environment–friendly, and heavy metal–free ozonolysis of olefins, which involves activated iodosylbenzene monomers, hydroxy–λ3–iodanes, as active species. Organocatalytic version of the oxidative cleavage of olefins that involves in situ generation of hypervalent aryl–λ3–iodanes as effective organocatalysts and the use of m–chloroperbenzoic acid as a stoichiometric terminal oxidant under metal–free conditions is described. Cyclic and acyclic olefins as well as aliphatic and aromatic alkynes were cleaved to carboxylic acids under the organocatalytic conditions.
Photofunctional silica gel beads have been developed as environmental conscious materials. The hydroxybenzophenone (Hbp) chromophore–bonded silica gel (SiO2) beads (1) were developed as UV–absorbents. 4,5–Dimethoxy–2–nitrobenzyloxycarbonyl (Nbz) chromophore–bonded SiO2 (2) was prepared in order to control the amounts and sites of functional group by a use of Nbz as a photolabile protecting group. Diacetoxyantimony tetraphenylporphyrinato chromophore (Sb(OAc)2tpp)–bonded SiO2 (3a) was packed in micro–channel reactor. The photoreaction of 3a with Et2NH induced the demetallation to give free base tetraphenylporphyrin chromophore (H2tpp)–bonded SiO2 (3b). The color change of the H2tpp–H–adsorbed SiO2 (4) under dry and humidity conditions was applied to a new type of humidity indicator without CoCl2. The Sb(OH)2tpp–H–adsorbed SiO2 (5) was used as visible light driven photocatalysts in dechlorination of 4–chlororophenol, epoxidation of cyclohexene, and bactericidal reaction of E. coli. Also dimethoxophosphorus tetraphenylporphyrine (P(OMe)2tpp–H)–adsorbed SiO2 (6b) was practically used to sterilization Legionella species naturally occurring in fountain.
Cyclophanes can provide the intriguing cyclic structure built by the aromatic components. In small–sized [2.n]metacyclophanes their unique physical and chemical properties are mainly due to transannular electronic effects in the forced proximity and particular orientation of two π systems. In order to gain deeper insight concerning this π electronic interaction we have carried out investigation of the diazo coupling reaction of the cyclophanes, estimation of the cationic character of the cyclophane diazonium salts, comparison of the cyclophane skeleton toward the spectral properties and reactivity, and introduction of the stilbene and oligothiophene units into the cyclophane structure. Conformations and molecular packing of the cyclophanes have been examined in terms of some weak interactions based on π electron system. We also have studied the cyclophanes having the anthracene, pyrene and fluorene moieties as the component in viewpoints of their spectral properties, reactivities and formation of the charge–transfer complexes. Conformations of flexible cyclophanes have been investigated by considering intramolecular weak interaction involving the π electron system.
Novel approaches on application of singlet oxygen for scale-up manufacturing are introduced. Instead of traditional conditions using gaseous oxygen and light, disproponation of hydrogen peroxide by molibdate ion allows in situ generation of singlet oxygen. Combination of the traditional method with microreactor also enables efficient scale-up. Details of these reports including key safety issues are discussed below.