INDUCTION OF phr GENE EXPRESSION BY PYRIMIDINE DIMERS IN Escherichia coli

The photoreactivating enzyme (PRE) is concerned with mainly two kinds of light wavelength. The PRE splits UVC (254 nm)-induced pyrimidine dimer by absorbing UVA (320–380 nm) or visible light in its chromophore. The present paper demonstrates that the phr gene expression was efficiently induced in an excision defective strain (uvrA∼) after irradiation by UVC and UVB (290-320 nm), but not by UVA and visible light. In addition, the induced activity was significantly depressed by irradiation with UVA and visible light. Therefore we conclude that the phr gene expression can be induced by pyrimidine dimers.     

Synthesis of 23,23-difluoro-25-hydroxyvitamin D3

23,23-Difluoro-25-hydroxyvitamin D₃ was synthesized from 6β-methoxy-3α,5-cyclo-23,24-dinor-5α-cholan-22-ol.     

Copper-catalyzed acylations of o-vinylbenzylzirconocene intermediate and synthetic application toward steroid skeleton

Benzylzirconocene intermediate, which was readily prepared by a reaction of o-alkoxymethylstyrene with `Cp₂Zr' under mild conditions, reacted with acyl chlorides in the presence of a catalytic amount of CuBr-SMe₂ to give ketone derivatives in moderate to good yields.     

Electron spin resonance study on polymerization of conjugated dienes by homogeneous catalyst derived from n-butyl titanate and triethylaluminum

Polymerizations of butadiene, penta-1,3-diene, and isoprene with n-butyl titanate–triethylaluminum catalyst are examined by ESR measurements on the polymerization state. At Al/Ti molar ratios greater than 2.9 where the conjugated dienes are polymerized, the polymerization system of butadiene always gives an ESR signal with a g value of 1.983 and with a hyperfine structure of about 19 components. This signal does not appear at all, even in the presence of the monomer, at Al/Ti molar ratios smaller than two where butadiene is not polymerized. The absorption intensity of the signal coincides fairly well with the concentration of polymer chain calculated from polymer yield and the molecular weight. On the basis of these facts, the signal is assigned to the growing end of polybutadiene with this catalyst. The structure of the growing end is proposed to have both two substituted π-allyl groups and an alkoxy group in coordination to titanium (III), by analysis of the hyperfine structure. The polymerization system of penta-1,3-diene and that of isoprene respectively, give a new signal with a g value of 1.983, although the signal for the former monomer has a hyperfine structure of 11 components and that for the latter monomer has no hyperfine structure. A structure for the growing end in the polymerization of each of these two monomers analogous to that of the growing end of polybutadiene is proposed.     

Reaction of prostacyclin methyl ester with benzenesulfenyl chloride preparation of stable prostacyclin analogs

Several phenyl sulfides including stable 5- and 7-phenylthioprostacyclins were obtained by the reaction of the vinyl ether ($\text{1}$) and prostacyclin methyl ester ($\text{5}$) with PhSCl.     

Organoaluminum catalyst for polymerization reaction. Synthesis of isotactic polyacetaldehyde by AIR3–alkali metal hydroxide catalysts in situ

The catalytic behavior of binary systems derived from AIR₃ and alkali metal hydroxide in a molar ratio of 1 to 0.5 in situ for stereospecific polymerization of acetaldehyde was studied for the purpose of preparation of isotactic polyacetal. The polymer obtained can be readily stretched to a film. The polymerization proceeds slowly (in ～20 hr). The polymer yield and stereospecificity of the polymerization by AlEt₃–LiOH (1:0.5) catalyst were not significantly changed by the nature of solvent or dilution as far as studied. AlEt₃–NaOH, AlEt₃–KOH, AlEt₃–CsOH, AliBu₃–LiOH and AlMe₃–LiOH in molar ratios of 1 to 0.5 behaved similarly. AlMe₃–NaOH, AlMe₃–KOH and AliBu₃–NaOH also gave isotactic polymer of high stereoregularity but in lower yields.     

Spontaneous Alternating Copolymerization via Zwitterion Intermediates

This article describes a new concept of copolymerization which occurs spontaneously without any added catalyst. A nucleophilic monomer (M_N) combines with an electrophilic one (M_E) to generate a zwitterion ^[+]M_N—M, which is responsible for the initiation and propagation of copolymerization. Twenty-three novel copolymerizations have been explored on the basis of the new concept. M_N monomers which have been investigated are five- and six-membered cyclic imino ethers, dihydro-2(3H)-furanimine, an azetidine, a cyclic phosphinic acid ester and a Schiff base; the M_E monomers include β-propiolactone, a cyclic dicarboxylic acid anhydride, a sultone, acrylic acid, acrylamide, a β-hydroxyalkyl acrylate and ethylenesulfonamide. In most combinations, alternating 1 : 1 copolymers were produced. In addition to the above-mentioned combinations, the alternating 1 : 1 copolymerization of cyclic phosphite with α-keto acid was discovered.     

Zirconocene-mediated and/or catalyzed unprecedented coupling reactions of alkoxymethyl-substituted styrene derivatives

Reactions of o-(alkoxymethyl)styrene derivatives with a stoichiometric amount of zirconocene-butene complex (zirconocene equivalent, "Cp(2)Zr") brought about an insertion of the zirconocene species into a benzylic carbon-oxygen bond. The oxidative insertion of Cp(2)Zr to the benzylic carbon-oxygen bond is a result of sequential reactions: (i) formation of zirconacyclopropane by the ligand exchange with o-(alkoxymethyl)styrene, (ii) elimination of the alkoxy group through an aromatic conjugate system giving metalated o-quinodimethane species, and (iii) transfer of zirconium metal to the benzylic position. Through use of a catalytic amount of "Cp(2)Zr", however, unprecedented homo-coupling reactions (dimerization) of o-(alkoxymethyl)styrene derivatives occurred to give a tetracyclic compound. On the other hand, reactions of o-(1-alkoxyisopropyl)styrene derivatives gave rise to the analogous tetracyclic compounds regardless of the amount of "Cp(2)Zr" (stoichiometric or catalytic). Heterocoupling product between o-(1-alkoxyisopropyl)styrene and styrene congeners was obtained in high cis stereo- and regioselectivity by treating o-(1-alkoxyisopropyl)styrene derivatives with "Cp(2)Zr" in the presence of an excess amount of styrene derivatives.     

Reversible cleavage and recombination of an acetylenic carbon-carbon bond on a tetrairon cluster coupled with a two-electron redox reaction

Two-electron reduction of [(eta5-C5H4Me)4Fe4(mu3-CH)2(mu3-CO)2](PF6)2 (1) results in the coupling of two methylidyne ligands to form (eta5-C5H4Me)4Fe4(HCCH)(mu3-CO)2 (2), the two-electron oxidation of which reproduces 1. Structures of 1 and 2 were determined by X-ray diffraction analysis.     

Electrochemical detection of ascorbic acid and serotonin at a boron-doped diamond electrode modified with poly(N,N-dimethylaniline)

The electrochemical oxidation of ascorbic acid (AA) and serotonin (5-HT) at a boron-doped diamond (BDD) electrode modified with poly(N,N-dimethylaniline) (PDMA) has been studied. The oxidation potentials of 5-HT and AA overlapped after mixing of the two chemicals, due to interference of AA at the bare BDD electrode. However, after modifying the BDD electrode with a cationic polymer (PDMA), the oxidation peaks of 5-HT and AA were separated. PDMA-coated BDD electrodes can be used for simultaneous detection of these species.