Direct synthesis of polysubstituted quinoline derivatives by InBr3-promoted dimerization of 2-ethynylaniline derivatives

InBr3 promotes the dimerization of 2-ethynylaniline derivatives containing an unsubstituted terminal carbon leading to the production of polysubstituted quinoline derivatives in good yield.     

Photorefractive effect in ferroelectric liquid crystals

In this paper, we review recent progress of research on the photorefractive effect of ferroelectric liquid crystals. The photorefractive effect is a phenomenon that forms a dynamic hologram in a material. The interference of two laser beams in a photorefractive material establishes a refractive index grating. This phenomenon is applicable to a wide range of devices related to diffraction optics including 3D displays, optical amplification, optical tomography, novelty filters, and phase conjugate wave generators. Ferroelectric liquid crystals are considered as a candidate for practical photorefractive materials. A refractive index grating formation time of 8–10 ms and a large gain coefficient are easily obtained in photorefractive ferroelectric liquid crystals.     

Synthesis and Structure–Activity Relationship of Vicenistatin,a Cytotoxic 20‐Membered Macrolactam Glycoside

We have developed two syntheses of vicenistatin and its analogues. Our first‐generation strategy included the rapid and sequential assembly of the macrocyclic lactam by using an intermolecular Horner–Wadsworth–Emmons reaction between the C3–C13 fragment and the C1–C2, C14–C19 fragment, followed by an intramolecular Stille coupling reaction. The second‐generation strategy utilized a ring‐closing metathesis of a hexaene intermediate to generate the desired 20‐membered macrolactam. This second‐generation strategy made it possible to prepare synthetic analogues of vicenistatin, including the C20‐ and/or C23‐demethyl analogues. Evaluation of the cytotoxic effect of these analogues indicated the importance of the fixed conformation of aglycon for determining the biological activity of the vicenistatins.     

Organic acid induced olefination reaction of lactones

(Z)-Selective olefination of several lactones with ketene silyl acetals was achieved by the catalysis of carbon acids (C-H acids) having a bis(triflyl)methyl group as an acidic functionality; in particular, the triple carbon acid having three bis(triflyl)methyl groups in phloroglucinol shows an excellent catalytic performance.     

Structure–Activity Studies on the Fluorescent Indicator in a Displacement Assay for the Screening of Small Molecules Binding to RNA

A series of xanthone and thioxanthone derivatives with aminoalkoxy substituents were synthesized as fluorescent indicators for a displacement assay in the study of small‐molecule–RNA interactions. The RNA‐binding properties of these molecules were investigated in terms of the improved binding selectivity to the loop region in the RNA secondary structure relative to 2,7‐bis(2‐aminoethoxy)xanthone (X2S) by fluorimetric titration and displacement assay. An 11‐mer double‐stranded RNA and a hairpin RNA mimicking the stem loop IIB of Rev response element (RRE) RNA of HIV‐1 mRNA were used. The X2S derivatives with longer aminoalkyl substituents showed a higher affinity to the double‐stranded RNA than the parent molecule. Introduction of a methyl group on the aminoethoxy moiety of X2S effectively modulated the selectivity to the RNA secondary structure. Methyl group substitution at the C1′ position suppressed the binding to the loop regions. Substitution with two methyl groups on the amino nitrogen atom resulted in reducing the affinity to the double‐stranded region by a factor of 40 %. The effect of methyl substitution on the amino nitrogen atom was also observed for a thioxanthone derivative. Titration experiments, however, suggested that thioxanthone derivatives showed a more prominent tendency of multiple binding to RNA than xanthone derivatives. The selectivity index calculated from the affinity to the double‐stranded and loop regions suggested that the N,N‐dimethyl derivative of X2S would be suitable for the screening of small molecules binding to RRE.     

Characterization of magnetic nanoparticles modified with thiol functionalized PAMAM dendron for DNA recovery

Magnetic nanoparticles (MNPs) modified with the thiol functionalized polyamidoamine (PAMAM) dendron were synthesized to estimate their DNA recovery capabilities. Aminosilane-modified MNPs and MNPs surrounded by a phospholipid (distearoylphosphatidylethanolamine (DSPE)) bilayer were used as core particles. Cystamine-core PAMAM dendrimers were reduced by dithiothreitol to dendron thiols and chemically conjugated to the core particles. Characterization of the synthesis revealed an increase of the surface amine charge from generation 1 (G1) to G6, starting with an aminosilane initiator. Particle size distribution analysis indicated that G6 PAMAM-modified MNPs exhibited monodispersity in an aqueous solution. G6 PAMAM-MNPs and G6 PAMAM-PE-MNPs synthesized by the proposed method have equivalent DNA recovery abilities to PAMAM-MNPs prepared by the conventional divergent synthesis method. In optimized conditions, 96% of λDNA was recovered using G6 PAMAM-PE-MNPs. Therefore, the method for preparing PAMAM-MNPs and PAMAM-PE-MNPs proposed in this study will be a novel approach for producing DNA carriers for efficient DNA purification by magnetic separation.     

Preparation of (Z)-1-fluoro-1-alkenyl carboxylates,carbonates and carbamates through chromium mediated transformation of dibromofluoromethylcarbinyl esters and the reactivity as double acyl group donors

CrCl₂/Mn-mediated transformation of various dibromofluoromethylcarbinyl esters including carboxylates, carbonates and carbamates provided 1-fluoro-1-alkenyl esters via [2,3]-sigmatropic rearrangement of ester group. Reaction proceeded by using CrCl₂/Mn system under mild conditions (in THF at room temperature) to give 1-fluoro-1-alkenyl esters in good yield with an excellent Z selective manner. 1-Fluoro-1-alkenyl ester thus obtained acts as a double acyl donor in the reaction with necleophiles such as amine, thiol, alcohol as well as bifunctional necleophiles such as ethylene diamine derivative.     

Is CO2 fixation promoted through the formation of DBU bicarbonate salt?

The bicyclic amidines, 1,8‐diazabicyclo [5.4.0]undec‐7‐ene (DBU) and 1,5‐diazabicyclo[4.3.0] non‐5‐ene (DBN), were used for the chemical fixation of carbon dioxide. The promotion for CO₂ fixation is often reported through the formation of a thermally unstable DBU or DBN bicarbonate salt. To examine the effects of the DBU or DBN bicarbonate salt, reactions of 2‐aminobenzonitrile with the DBU salt or DBN salt in dimethylformamide (DMF) were performed at 20°C for 24 h in argon or carbon dioxide (0.1 MPa). However, in all the cases, 1H‐quinazoline‐2,4‐dione was not obtained completely. In contrast with room temperature reactions, 2‐aminobenzonitriles and DBU bicarbonate salt in DMF reacted for 4 h under high temperature (80°C) and CO₂ atmosphere (0.1 MPa) gave 1H‐quinazoline‐2,4‐diones in good to excellent yields. At high‐temperature conditions, DBU bicarbonate salt is decomposed to DBU and carbon dioxide. Also, the carbonylation of 2‐aminobenzonitrile using DBU and carbon dioxide afforded 1H‐quinazoline‐2,4‐dione in good yields under similar reaction conditions. These results suggest that the combination of DBU or DBN as a strong base and carbon dioxide is much more important than the in situ formation of DBU or DBN bicarbonate salt for the acceleration of CO₂ fixation. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:276–280, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21014