Synthesis and properties of thermoplastic propyl-etherified amylose

Amylose was etherified with 1-bromopropane in DMSO. The degree of substitution (DS) was varied by altering the feed ratio of 1-bromopropane. The structures of the products were characterized by IR and 1H-NMR spectroscopy. When the molar feed ratio of 1-bromopropane to hydroxyl groups of amylose was beyond 7.5, the hydroxyl groups were completely substituted with propyl ether groups. The etherified amylose with DS 1.9 showed a glass transition temperature (T_g), and that with DS 2.3 or 3.0 showed both T_g and melting temperature (T_m) (DS 3.0 means complete substitution). The etherification imparted melt processability and solubility in nonpolar organic solvent to amylose.     

An Isolable Radical Anion of an Organosilicon Cluster Containing Only σ Bonds

The radical anion of octa‐tert‐butyloctasilacubane was generated and isolated. The EPR spectrum showed the satellites due to the tertiary ¹³C nuclei of the eight tert‐butyl groups. The X‐ray crystallographic analysis showed that the Si? Si bonds are shortened and the Si? C bonds are elongated compared with those of octa‐tert‐butyloctasilacubane. These results are well explained by the distribution of an unpaired electron in the singly occupied molecular orbital (SOMO).     

Lobohedleolide and (7Z)-lobohedleolide,new cembranolides from the soft coral lobophytum hedleyi whitelegge

The structures of lobohedleolide (1) and (7Z)-lobohedleolide (2), two new cembranolides containing the α,β-unsaturated carboxylic acid system isolated from the Japanese soft coral Lobophytum hedleyi Whitelegge, were elucidated from spectral and chemical evidence, and the absolute configuration of (1) was determined by X-ray analysis of its p-bromophenacyl ester (9). Lobohedleolide (1) showed growth inhibition of the in vitro Hella cells.     

Trehalose and trehalose-based polymers for environmentally benign, biocompatible and bioactive materials

Trehalose is a non-reducing disaccharide that is found in many organisms but not in mammals. This sugar plays important roles in cryptobiosis of selaginella mosses, tardigrades (water bears), and other animals which revive with water from a state of suspended animation induced by desiccation. The interesting properties of trehalose are due to its unique symmetrical low-energy structure, wherein two glucose units are bonded face-to-face by 1-->1-glucoside links. The Hayashibara Co. Ltd., is credited for developing an inexpensive, environmentally benign and industrial-scale process for the enzymatic conversion of alpha-1,4-linked polyhexoses to alpha,alpha-D-trehalose, which made it easy to explore novel food, industrial, and medicinal uses for trehalose and its derivatives. Trehalosechemistry is a relatively new and emerging field, and polymers of trehalose derivatives appear environmentally benign, biocompatible, and biodegradable. The discriminating properties of trehalose are attributed to its structure, symmetry, solubility, kinetic and thermodynamic stability and versatility. While syntheses of trehalose-based polymer networks can be straightforward, syntheses and characterization of well defined linear polymers with tailored properties using trehalose-based monomers is challenging, and typically involves protection and deprotection of hydroxyl groups to attain desired structural, morphological, biological, and physical and chemical properties in the resulting products. In this review, we will overview known literature on trehalose's fascinating involvement in cryptobiology; highlight its applications in many fields; and then discuss methods we used to prepare new trehalose-based monomers and polymers and explain their properties.     

Screening search for organic fluorophores: syntheses and fluorescence properties of 3-azolyl-7-diethylaminocoumarin derivatives

In order to find a highly sensitive fluorophore, 3-azolyl-7-diethylaminocoumarin derivatives were synthesized. Both the absorption and fluorescence maxima of the coumarin-thiazole compounds showed red shifts with increases of the molar absorptivities and fluorescence intensities, in comparison with those of the corresponding coumarin-oxazole compounds. Among them, 3-(5-ethoxycarbonyl-1,3-thiazol-2-yl)-7-diethylamino-2H-chromen -2-one (3e) was one of the most promising candidates as a fluorophore accessible for analytical purposes in the fields of analytical and biological chemistry.     

Computational Design of Single-Peptide Nanocages with Nanoparticle Templating

Protein complexes perform a diversity of functions in natural biological systems. While computational protein design has enabled the development of symmetric protein complexes with spherical shapes and hollow interiors, the individual subunits often comprise large proteins. Peptides have also been applied to self-assembly, and it is of interest to explore such short sequences as building blocks of large, designed complexes. Coiled-coil peptides are promising subunits as they have a symmetric structure that can undergo further assembly. Here, an α-helical 29-residue peptide that forms a tetrameric coiled coil was computationally designed to assemble into a spherical cage that is approximately 9 nm in diameter and presents an interior cavity. The assembly comprises 48 copies of the designed peptide sequence. The design strategy allowed breaking the side chain conformational symmetry within the peptide dimer that formed the building block (asymmetric unit) of the cage. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) techniques showed that one of the seven designed peptide candidates assembled into individual nanocages of the size and shape. The stability of assembled nanocages was found to be sensitive to the assembly pathway and final solution conditions (pH and ionic strength). The nanocages templated the growth of size-specific Au nanoparticles. The computational design serves to illustrate the possibility of designing target assemblies with pre-determined specific dimensions using short, modular coiled-coil forming peptide sequences.     

Nucleosides and Nucleotides. 151. Conversion of (Z)-2'-(Cyanomethylene)-2'-deoxyuridines into Their (E)-Isomers via Addition of Thiophenol to the Cyanomethylene Moiety Followed by Oxidative Syn-elimination Reactions(1)

The Wittig reaction of 1-[3,5-O-(1,1,3,3-tetraisopropyldisiloxane-1,3-diyl)-beta-D-erythro-pentofuranos-2-ulosyl]uracil (6) with Ph(3)P=CHCN afforded (Z)-2'-cyanomethylene derivative 7 exclusively. The (E)-isomer was accessed from its (Z)-isomer through a sequence of addition of thiophenol to the 2'-cyanomethylene moiety of the (Z)-isomer from the alpha-face, selectively, and stereoselective oxidative syn-elimination of the resulting adduct. The diastereofacial selectivity of the benzenethiolate addition to the cyanomethylene moiety was found to be influenced by participation of the 2-carbonyl group at the base moiety and steric hindrance of the sugar protecting groups. Although nucleophilic addition reactions at the 2'-position of 6 have been well-known to occur from the alpha-face selectively, treatment of 7 with LiSPh in THF unexpectedly afforded a mixture of alpha- and beta-phenylthio derivatives 8 and 9 in almost equal ratio. Furthermore, an unusual beta-facial selective addition was observed on treatments of 7 with PhSAlMe(2) in CH(2)Cl(2) or with LiSPh in the presence of Mg(ClO(4))(2) in THF. On the other hand, when (Z)-2'-(cyanomethylene)-5'-O-triisopropylsilyl derivative 10 was treated with LiSPh, the alpha-phenylthio derivative 13 was obtained predominantly (89:11). Oxidation of 8 with m-chloroperbenzoic acid (m-CPBA) in CH(2)Cl(2) and pyrolysis of the resulting sulfoxides afforded the (Z)-isomer 7 exclusively. Treatment of 13 with m-CPBA under the same conditions afforded the desired (E)-cyanomethylene derivatives 18 as a major product (E:Z = 14:1) in good yield. Deprotection of 18 by the standard procedures furnished (E)-2'-(cyanomethylene)-2'-deoxyuridine (5).     

Synthesis and photocuring of cinnamoyl trehalose esters

A trehalose cinnamoyl ester (TC) was synthesized from trehalose and cinnamoyl chloride in dimethylformamide (DMF) in the presence of triethylamine and 4‐(N,N‐dimethylamino)pyridine. The product was characterized by ¹H NMR spectroscopy to reveal that the reaction proceeded. Two different types of TCs were synthesized by changing the feed ratio of cinnamoyl chloride to trehalose. When the feed ratio of cinnamoyl chloride to trehalose was 8 (TC8), the degree of substitution (DS) was 8.0, while it was 4.2 when the feed ratio was 4 (TC4). Photocuring was confirmed by observing changes in UV absorption spectrum and FT Infrared (IR) spectrum. After 5 min of UV irradiation, solubility in chloroform significantly decreased. A transparent thin coating film of TC was easily prepared by casting from a chloroform solution on a Petri dish and UV irradiation was carried out over a simple photomask. After TC within the non‐irradiated region was removed by flash soaking with chloroform, the shape of the photomask appeared. A scanning electron microscope (SEM) measurement revealed that the surface of the photocured coating film was smooth and that the edge of the photocured TC had a characteristic feature. Biodegradation of the photocured TC and non‐irradiated TC was examined by the biochemical oxygen demand (BOD) method using activated sludge. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis of thietane nucleoside with an anomeric hydroxymethyl group

Thietane nucleoside 5 with an anomeric hydroxymethyl group was synthesized via the Pummerer reaction. The stereochemistry of the sulfoxide and the nature of the protecting group had no significant effect on the yield of the reaction. When a hypervalent iodine reagent was used, sulfide 16 with O-benzoyl protecting groups gave the ring-expanded nucleoside 21. Unfortunately, synthesized compound 6 did not exhibit anti-HSV activity.