Stereospecific Synthesis of a Dihydroxyethylene Isostere of Cyclohexylalanine Amide, (2S,3R,4S)-4-Amino-5-Cyclohexyl-1-Morpholino-2,3-Pentanediol(ACMP) from a Protected Sugar

ABSTRACT

A transition-state analogue of a renin inhibitor at the scissile site, a dihydroxyethylene isostere of cyclohexylalanine amide, (2S,3R,4S)-4-amino-5-cyclohexyl-1-morpholino-2,3-pentanediol(ACMP), was synthesized from 1,2:5,6-di-O-isopropylidene-α-D-allofuranose stereospecifically.     

Online tool for calculating null points in various inversion recovery sequences

Accurate equations for calculating the inversion time of the null point (TI_null) in inversion recovery (IR) sequences are required for adequate suppression of fat or cerebrospinal fluid (CSF) but are not widely known. The purpose of this study is to elucidate the process of deriving accurate TI_null equations using schematic diagrams that allow the equations to be easily understood, and to devise a convenient online tool for instant calculation of TI_null.     

Chemical and Genetic Study of Ligularia anoleuca and L. veitchiana in Yunnan and Sichuan Provinces of China

Chemical and genetic study of Ligularia anoleuca and L. veitchiana, which belong to section Ligularia, series Speciosae, was carried out. From L. anoleuca samples, collected in Yunnan and Sichuan Provinces of China, a new compound, furanoeremophil‐1(10)‐en‐6α‐ol, was isolated together with known 6β‐{[2‐(hydroxymethyl)prop‐2‐enoyl]oxy}furanoeremophil‐1(10)‐ene and 1β,10β‐epoxy‐6β‐{[2‐(hydroxymethyl)prop‐2‐enoyl]oxy}furanoeremophilane. From L. veitchiana samples, collected in Yunnan Province, euparin, 2‐isopropenyl‐5,6‐dimethoxybenzofuran, and 6‐hydroxy‐3β‐methoxytrementone were isolated. DNA Sequencing of the internal transcribed spacers of the ribosomal RNA gene showed that the two species are not particularly close despite morphological similarities, in agreement with the chemical results.     

Growth and characterization of Fe nanostructures on GaN

We have investigated the growth of Fe nanostructures on GaN(0 0 0 1) substrates at room temperature using reflection high-energy electron diffraction (RHEED), scanning tunneling microscopy (STM), and superconducting quantum interference device magnetometer. Initially, a ring RHEED pattern appears, indicating the growth of polycrystalline α-Fe. At around 0.5 nm deposition, the surface displays a transmission pattern from α-Fe films with the epitaxial relationship of Fe(1 1 0)//GaN(0 0 0 1) and Fe[1 −1 1]//GaN[1 1 −2 0] (Kurdjumov-Sachs (KS) orientational relationship). Further deposition to 1 nm results in the appearance of a new spot pattern together with the pattern from domains with the KS orientation relationship. The newly observed pattern shows that Fe layers are formed with the epitaxial relationship of Fe(1 1 0)//GaN(0 0 0 1) and Fe[0 0 1]//GaN[1 1 −2 0] (Nishiyama-Wasserman (NW) orientational relationship). From STM images for Fe layers with the KS and NW orientational relationships, it can be seen that Fe layers with the KS relationship consist of round-shaped Fe nanodots with below 7 nm in average diameter. These nanodots coalesce to form nanodots elongating along the Fe[1 0 0] direction, and they have the KS orientational relationship. Elongated Fe nanodots with the NW relationship show ferromagnetism while round-shaped Fe nanodots with the KS relationship show super-paramagnetic behavior. We will discuss their magnetic properties in connection with the change in crystalline configurations of nanodots.     

Pursuit of reinitiation efficiency of resonance‐stabilized monomeric allyl radical generated via “degradative monomer chain transfer” in allyl polymerization

For a deeper understanding of allyl polymerization mechanism, the reinitiation efficiency of resonance‐stabilized monomeric allyl radical was pursued because in allyl polymerization it is commonly conceived that the monomeric allyl radical generated via the allylic hydrogen abstraction of growing polymer radical from monomer, i.e., “degradative monomer chain transfer,” has much less tendency to initiate a new polymer chain and, therefore, this monomer chain transfer is essentially a termination reaction. Based on the renewed allyl polymerization mechanism in our preceding article, the monomer chain transfer constant in the polymerization of allyl benzoate was estimated to be 2.7 × 10^?2 at 80 °C under the polymerization condition, where the coupling termination reaction of growing polymer radical with allyl radical was negligible and, concurrently, the reinitiation reaction of allyl radical was enhanced significantly. The reinitiation efficiencies of monomeric allyl radical were pursued by the dead‐end polymerizations of allyl benzoate at 80, 105, and 130 °C using a small amount of initiators; they increased remarkably with raised temperature. Thus, the enhanced reinitiation reactivity of allyl radical at an elevated temperature could bias the well‐known degradative monomer chain transfer characteristic of allyl polymerization toward the chain transfer in common vinyl polymerization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

RNA‐Aligned Film Prepared from an RNA/Lipid Complex

Strong films were prepared from an RNA/lipid complex by casting from organic solutions. RNA (mainly tRNA) was extracted from yeasts, followed by a replacement of the sodium counterions of the tRNA phosphate units by cationic amphiphiles. RNA units in the RNA/lipid film could be aligned in one direction by stretching due to the presence of intermolecular hydrogen bonds. The film showed physical strength and was biodegradable.     

New approach to block copolymerization of ethylene with polar monomers by the unique catalytic function of organolanthanide complexes

This paper describes the first examples of ABA‐ and AB‐type block copolymerizations of a nonpolar monomer, in this case ethylene, with polar monomers, such as methyl methacrylate (MMA), ϵ‐caprolactone (CL), and 2,2‐dimethyltrimethylene carbonate (DTC), initiated by the unique catalytic function of rare earth metal complexes [Sm(II) and Ln(III) (Ln = Y, Sm)] as initiators. The Sm(II) species conducts the ABA‐type triblock copolymerization, leading to poly(MMA‐co‐ethylene‐co‐MMA), poly(CL‐co‐ethylene‐co‐CL), or poly(DTC‐co‐ethylene‐co‐DTC) by the efficient catalysis of racemic Me₂Si(C₅H₂‐2‐Me₃Si‐4‐tBu)₂Sm(THF)₂ ( 1 ) or meso Me₂Si(Me₂SiOSiMe₂)(C₅H₂‐3‐tBu)Sm(THF) ( 2b ). The resulting block copolymers are completely insoluble in THF and CHCl₃, but the homopolymers of MMA, CL, and DTC are freely soluble in these solvents. TEM profiles provide direct evidence for the block copolymerizations, where the spheric morphology of homogeneously dispersed polar polymers was observed. Ln(III) species, such as racemic Me₂Si(C₅H₂‐2‐Me₃Si‐4‐tBuMe₂Si)YH ( 5 ) and Me₂Si(C₅H₂‐2‐Me₃Si‐4‐tBu)SmH ( 6 ), afford AB‐type block copolymers between ethylene and MMA or CL, whose TEM images reveal the homogeneous dispersion of poly(MMA) or poly(CL) units in the polyethylene region. The ABA‐ and AB‐type block copolymers demonstrate high break stress and high tensile modulus as compared with their corresponding blended polymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4095–4109, 2000