Synthetic Study of (−)‐Norzoanthamine: Construction of the ABC Ring Moiety

Throw your hat in the ring : A highly diastereoselective synthesis of the ABC rings of (?)‐norzoanthamine has been achieved starting from the (?)‐Hajos–Parrish ketone (see scheme). Three asymmetric quaternary carbon centers on the C ring were constructed by a 1,4‐addition, and an intramolecular Diels–Alder reaction provided a trans‐decalin scaffold on the AB rings.

     

Incorporation of Pseudo‐complementary Bases 2,6‐Diaminopurine and 2‐Thiouracil into Serinol Nucleic Acid (SNA) to Promote SNA/RNA Hybridization

Serinol nucleic acid (SNA) is a promising candidate for nucleic acid‐based molecular probes and drugs due to its high affinity for RNA. Our previous work revealed that incorporation of 2,6‐diaminpurine (D), which can form three hydrogen bonds with uracil, into SNA increases the melting temperature of SNA‐RNA duplexes. However, D incorporation into short self‐complementary regions of SNA promoted self‐dimerization and hindered hybridization with RNA. Here we synthesized a SNA monomer of 2‐thiouracil (sU), which was expected to inhibit base pairing with D by steric hindrance between sulfur and the amino group. To prepare the SNA containing D and sU in high yield, we customized the protecting groups on D and sU monomers that can be readily deprotected under acidic conditions. Incorporation of D and sU into SNA facilitated stable duplex formation with target RNA by suppressing the self‐hybridization of SNA and increasing the stability of the heteroduplex of SNA and its complementary RNA. Our results have important implications for the development of SNA‐based probes and nucleic acid drugs.     

Acyl Fluorides in Late‐Transition‐Metal Catalysis

In this Review, we summarize the current state of the art in late‐transition‐metal‐catalyzed reactions of acyl fluorides, covering both their synthesis and further transformations. In organic reactions, the relationship between stability and reactivity of the starting substrates is usually characterized by a trade‐off. Yet, acyl fluorides display a very good balance between these properties, which is mostly due to their moderate electrophilicity. Thus, acyl fluorides (RCOF) can be used as versatile building blocks in transition‐metal‐catalyzed reactions, for example, as an “RCO” source in acyl coupling reactions, as an “R” source in decarbonylative coupling reactions, and as an “F” source in fluorination reactions. Starting from the cleavage of the acyl C?F bond in acyl fluorides, various transformations are accessible, including C?C, C?H, C?B, and C?F bond‐forming reactions that are catalyzed by transition‐metal catalysts that contain the Group 9–11 metals Co, Rh, Ir, Ni, Pd, or Cu.     

A new secolactarane-type sesquiterpene from Strobilurus tephanocystis

A new sesquiterpenoid, strobiluric acid has isolated from the liquid culture extract of the fungus Strobilurus stephanocystis together with seven known sesquiterpenoids. Their structures were established based on spectroscopic data.     

Amphiphilic molecular design as a rational strategy for tailoring bicontinuous electron donor and acceptor arrays: photoconductive liquid crystalline oligothiophene--C60 dyads

For tailoring solution-processable optoelectronic thin films, a rational strategy with amphiphilic molecular design is proposed. A donor-acceptor dyad consisting of an oligothiophene and C60, when modified with a hydrophilic wedge on one side and a paraffinic wedge on the other (1Amphi), forms over a wide temperature range a photoconducting smectic A liquid crystal having bicontinuous arrays of densely packed donor and acceptor units. In contrast, when modified with only paraffinic wedges (1Lipo), the dyad forms a smectic A liquid crystalline mesophase, which however is poorly conductive. As indicated by an absorption spectral feature along with a synchrotron radiation small-angle X-ray scattering profile, 1Lipo in the lamellar structure does not adopt a uniform head/tail orientation. Such defective donor and acceptor arrays likely contain a large number of trapping sites, leading to short-lived charge carriers, as observed by a flash photolysis time-resolved microwave conductivity study.     

Evaluation of image sticking property on liquid crystal displays with polymer layers produced from phenanthrene-carrying monomers

As a model of polymer-sustained-alignment liquid crystal display (PSA-LCD), the liquid crystal (LC) cells having the polymer layers produced from monomers of phenanthrene (Phen)-carrying monomers, 2,7-, 3,8-, 1,8- and 3,6-dimethacryloyl-oxy-phenanthrene (DMAPhen), were prepared and investigated image sticking phenomenon with evaluations of residual direct current voltage (V_rDC) and difference in pretilt angle before and after application of alternate current voltage (Δtilt). The V_rDC values were small for the LC cells with the polymer layers produced from the Phen-carrying monomers used in this study. On the other hand, Δtilt depends on the molecular structure of the Phen-carrying monomer. The Δtilt values became small with increasing the linearity of the monomer structure for the Phen-carrying monomers. The findings would be useful for obtaining the small level of image sticking in the PSA-LCDs produced from the Phen-carrying monomers.     

Capillary gas chromatography/negative ion chemical ionization mass spectrometry for the quantification of bile acids including 1 beta-hydroxylated and unsaturated bile acids in serum and urine

12 bile acids, including 1 beta-hydroxylated and unsaturated bile acids, have been quantified by capillary gas chromatography/negative ion chemical ionization mass spectrometry, using the trimethylsilyl(TMS) ether derivatives of bile acid pentafluorobenzyl(PFB) esters. The analysis time is 12 min and the minimum measurable amount is 100 fg for each bile acid. Bile acids in 200 microL of serum and 50 microL of urine from healthy human adults were measured. These small sample sizes enhance the practicality of using this method as a screening test for bile acids in the serum and urine of human infants, where small sample size is a major problem.     

Molecular orientation and mechanical anisotropy of polypropylene sheet containing N,N′‐dicyclohexyl‐2,6‐naphthalenedicarboxamide

Effect of mixing and processing conditions at T‐die extrusion on the structure and mechanical properties is studied for isotactic polypropylene (PP) containing a small amount of β‐form nucleating agent, N,N′‐dicyclohexyl‐2,6‐naphthalenedicarboxamide. It is found that trigonal β crystals are predominantly formed in the extruded samples containing the nucleating agent irrespective of the mixing and processing conditions, leading to the marked mechanical toughness. On the contrary, the molecular orientation is significantly affected by the mixing and processing conditions. In particular, it should be noted that PP molecules in the extruded sheet which was mixed at high temperature (260 °C) and extruded at low temperature (200 °C) orient perpendicular to the applied flow direction. As a result, the sheet shows anomalous mechanical anisotropy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 424–433, 2009