High‐Yielding Synthesis of the Anti‐Influenza Neuramidase Inhibitor (−)‐Oseltamivir by Three “One‐Pot” Operations

Taking shortcuts : A remarkably short and high‐yielding asymmetric total synthesis of (?)‐oseltamivir takes advantage of organocatalysis and single‐pot domino operations. The target, known as the drug Tamiflu, is prepared efficiently in a short time, and also its derivatives can be synthesized effectively.

     

p-Phenylenediamine Epoxy Resin Film for Redox Enzyme Detection

Summary: Phenylenediamine derivatives (PDs) are environmentally hazardous, though very useful for chemical analysis. To minimize release into the environment, a PD-containing epoxy resin film was developed that retained redox enzyme activity. p-Phenylenediamine and 2,2-bis(4-glycidyloxyphenyl)-propane were cured to produce a violet film. This film was reactive against peroxidase, a redox enzyme that oxidizes phenylenediamine to afford an imine. Enzymatic oxidation caused the film to change color from violet to deep green. The film exhibited fluorescence at 394 nm under excitation at 350 nm, and the fluorescent intensity decreased with greater oxidation. Thus, the film could be used to detect redox enzyme activity.     

Regioregulated Syntheses of Poly(aminopyridine)s by Pd‐catalyzed Amination Reaction

Regioregulated poly(aminopyridine)s were synthesized by a Pd‐catalyzed C N coupling reaction. The polymerization using Pd(0) and a bulky monodentate phosphine ligand distinctively produced the para‐linked and meta‐linked poly(aminopyridine)s, without the need for a protection process. The regioregularity of the polymer was confirmed by ¹H NMR spectroscopy. Model reactions were studied to evaluate the possibility of crosslinkage in the polymer. A large difference in reactivity was observed between 5‐amino‐2‐bromopyridine and 2‐amino‐5‐bromopyridine, which should have afforded same product. Density functional theory (DFT) calculations indicated that electron densities of the Br‐bound carbon atom and the pyridine‐nitrogen atom determine the reactivity of the monomers.

     

Nanocopying of individual DNA strands and formation of the corresponding surface pattern of titania nanotube

Titania nanotube was prepared by nanocopying of the individual DNA double strand as template. DNA was first spread on a solid substrate, and its molecular surface was coated with an ultrathin titania layer by 3 cycles of the surface sol-gel process. Fluorescence microscopic images before and after titania coating of the DNA/YOYO-1 complex were essentially identical, showing that the titania coating did not change the chemical properties of the complex. Titania coating effectively prohibited chemical degradation of titania-coated DNA with DNase I and physically separated the DNA strand from the surrounding environment with an ultrathin titania barrier. The morphology of the DNA strand was preserved, as confirmed by microscopic and spectroscopic observations. The presence of the hollow (tubular) structure was confirmed by a silver staining experiment coupled with scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy (STEM-EDX) analysis. The present finding shows the effectiveness of nanocopying of the individual DNA strand.     

Rare-earth silylamide-catalyzed selective dimerization of terminal alkynes and subsequent hydrophosphination in one pot

[reaction: see text] Rare-earth silylamides, Ln[N(SiMe3)2]3 (Ln = Y, La, Sm), catalyzed regio- and stereoselective dimerization of terminal alkynes in the presence of amine additives to give conjugated enynes in high yields. The additives played a crucial role to depress the oligomerization and to control the regio- and stereochemistry of the dimerization. Thus, the selectivity for (Z)-head-to-head enynes was increased in the order of tertiary < secondary < primary amine additives. On the other hand, the reversed order was observed for the formation of head-to-tail dimers. When alpha,omega-diynes were subjected to the dimerization, very novel cyclic bisenyne compounds were given through double-dimerization in satisfactory yields. In addition, an application of the system allowed subsequent hydrophosphination of the enynes generated in situ with diphenylphosphine, giving rise to 1-phosphinyl-1,3-dienes as the sole products in excellent yields after oxidative workup.     

Total synthesis of (-)-ascochlorin via a cyclobutenone-based benzannulation strategy

The application of a convergent benzannulation strategy in an efficient synthesis of (-)-ascochlorin is described.     

Two new meroterpenoids, penisimplicin A and B, isolated from Penicillium simplicissimum

In the course of our research for new antifungal agents, two new meroterpenoids, penisimplicin A (1) and B (2), were isolated from Penicillium simplicissimum. The absolute structures of 1 and 2 were established by spectroscopic and chemical investigation. Penisimplicin A (1) and B (2) are rare examples of D-ring seco-meroterpenoids. Since compounds 1 and 2 showed no antifungal activities, the isolation of the compounds with antifungal activity will be attempted.     

Solution properties of celluloses from different biological origins in LiCl · DMAc

Differences in the solution properties of cellulose in 8%LiCl·DMAc (dimethyl acetamide) were investigated usingcelluloses from different origins. The latter included plants (dissolving pulp(DP), cotton linters (CC), and kraft pulp), bacteria (Acetobacterxylinum, BC), and marine animals (tunicin fromHalocynthia). The celluloses from plants and bacteriaformed LiCl·DMAc solutions that were isotropic andanisotropic, respectively; and the animal cellulose was insoluble. The weightaverage molecular weights, M_w, of DP, CC and BC were found to be98.2×10⁴,170×10⁴ and192×10⁴, respectively. The solutionviscositieswere proportional to c (c; polymer concentration) in thedilute and semi-dilute regions, where the exponent was 1 for allsamplesin the dilute region; in the semi-dilute region, it was 4 for the DP and CCsolutions and 3 for the BC solution. Molecular weight differences werecompensated by plotting the viscosity against cM_w orc[] (where [] is the limiting viscosity number).The difference in viscosity behavior at elevated solutionconcentration indicates that the cellulose molecules from DP and CC behave asflexible polymer chains and those of BC as rod-like ones.These results suggest that differences in molecular structure andproperties exist between celluloses from different sources, and that thesedifferences relate to the mechanism or the type of the intermolecularinteraction between the celluloses of plants (DP and CC) and those of bacteria(BC).