Monte Carlo structural investigation of helical poly(β-l-aspartate)s containing linear alkyl side chains

Three representative members of the family of poly(α-alkyl β-l-aspartate)s (PAALA-12, -16 and -18) have been investigated using Monte Carlo simulation of an atomistically explicit model. At the temperatures investigated, the main chains (helices) are arranged in highly regular layers, while the space between layers is filled by the alkyl side chains. The molecular structure of the inter-layer region is found to be very approximately liquid-like. The simulations are also able to predict the anomalous (densification) behavior of the PAALAs as the temperature is raised through the transition value.     

Efficient α-chlorination of carbonyl containing compounds under basic conditions using methyl chlorosulfate

An efficient method for the α-chlorination of ketones under basic conditions is described using methyl chlorosulfate. Its applicability for the chlorination of other functional groups has also been studied and it is equally useful for the synthesis of α-chloroesters and amides. Methyl chlorosulfate is described for the first time as a positive chlorine source. Some aldol reactions which occur during the chlorination of some substrates are also reported.     

Two new compounds from Zingiber officinale

A new cyclic diarylheptanoid,1,5-epoxy-3-hydroxy-1-(3-methoxy-4,5-dihydroxyphenyl)-7-(4-hydroxyphenyl)-heptane (1),as well as a new monoterpene,10-O-β-D-glucopyranosyl-hydroxy cineole (2) were isolated from the rhizomes of Zingiber officinale. The structures of compounds 1 and 2 were established based on their spectral data.In addition,the antioxidant activities of these compounds were also measured.     

Two new compounds derived from bufalin

The biotransformation of bufalin by cell suspension cultures of Platycodon grandiflorus was investigated and two new biotransformed products were obtained,which was 3-epi-telocinobufagin and 3-epi-bufalin-3-O-β-D-glucoside.     

Synthesis and characterisation of main‐chain hydrogen‐bonded supramolecular liquid crystalline complexes formed by azo‐containing compounds

A series of azopyridine‐containing hydrogen bonding acceptors (4a–c) with flexible spacers of oligo(methylene) were synthesised. Hydrogen‐bonded polymeric complexes 4/5 and trimeric complexes 4/6₂ , where 5 and 6 are aromatic dicarboxylic acids and monocarboxylic acids, respectively, were prepared and their liquid crystallinity was examined using differential scanning calorimetry and polarising optical microscopy. The study showed that most of the complexes displayed reversible thermotropic nematic phase. The isotropic to nematic phase transition temperatures of polymeric complexes 4/5 and trimeric complexes 4/6₂ in general decreased with the increase in length of spacers and terminal groups in the corresponding proton acceptors 4 and the proton donors 5 and 6, respectively. Hydrogen bonding interactions in complexes 4/5 and 4/6₂ were studied by X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy.     

Two new phenolic compounds from Artemisia sphaerocephala

Two new phenolic compounds were isolated from whole plant of Artemisia sphaerocephala. The structures were elucidated on the basis of spectroscopic methods as 4-(1-hydroxylethyl)-phenol-1-O-b-D-glucopyranoside and 4-O-acetophenone-b-D-gluco- pyranosyl-(1-3)-b-D-glucopyranoside.     

Two new phenolic compounds from Ardisia gigantifolia

Two new compounds were isolated from the 60% ethanol extract of the dried rhizome of Ardisia gigantifolia Stapf. The structures were elucidated on the basis of spectroscopic methods as （＋）-5-（1,2-dihydroxypentyl）-benzene- 1,3-diol and （-）-5-（1,2- dihydroxypentyl）benzene- 1,3-diol.     

Sulfoxide-mediated α-arylation of carbonyl compounds

A novel sulfoxide-mediated α-arylation of carbonyl compounds is reported. This reaction proceeds under very mild conditions at room temperature and does not require any transition-metal promoter or catalyst.     

Conformational study of α-phenylthiocarbonyl compounds

Electrical and electrooptical characteristics of-phenylthioacetone,-phenylthiocyclohexanone, and-phenylthio-4-caranone have been determined and used in establishing the structure of the compounds in solution. It has been shown that the preferred conformer with respect to the bond , is the ac-conformer [(O=C-C-S)>90°], in which the gauche conformer with respect to the C-S bond is realized, with a 1,3-parallel position of the C=O and S-Ph bonds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2483–2488, November, 1991.     

Two new supramolecular compounds based on Ni(II)-Schiff-base and Keggin-type [PMo12O40]3−

Two polyoxometalate-templated nickel-Schiff-base compounds, {[Ni(L)₂]₂[PMo₁₂O₄₀][Cl] · 1.5DMF · H₂O} _n (1) and {[Ni(L)₂]₂[PMo₁₂O₄₀][Cl] · DMSO · CH₃OH · 0.5H₂O} _n (2) (where L is 1,4-bis(4-imidazolyl)-2,3-diaza-1,3-butadiene), were synthesized in situ from Ni²⁺ and L in H₂O/DMF/CH₃OH or H₂O/DMSO/CH₃OH at room temperature and characterized by elemental analysis, infrared spectroscopy, and single-crystal X-ray diffraction analysis. The results of the single-crystal X-ray diffractions suggested that both compounds have the same packing of the Ni(II)-Schiff-base cation layer and Keggin anion layer. Thermogravimetric analyses suggested that two supramolecular compounds have similar thermal stabilities based on the same packing of the cation and anion layers.     

Translocation of α-helix chains through a nanopore

The translocation of α-helix chains through a nanopore is studied through Langevin dynamics simulations. The α-helix chains exhibit several different characteristics about their average translocation times and the α-helix structures when they transport through the nanopores under the driving forces. First, the relationship between average translocation times τ and the chain length N satisfies the scaling law, τ～N(α), and the scaling exponent α depends on the driving force f for the small forces while it is close to the Flory exponent (ν) in the other force regions. For the chains with given chain lengths, it is observed that the dependence of the average translocation times can be expressed as τ～f(-1/2) for the small forces while can be described as τ～f in the large force regions. Second, for the large driving force, the average number of α-helix structures N(h) decreases first and then increases in the translocation process. The average waiting time of each bead, especially of the first bead, is also dependent on the driving forces. Furthermore, an elasticity spring model is presented to reasonably explain the change of the α-helix number during the translocation and its elasticity can be locally damaged by the large driving forces. Our results demonstrate the unique behaviors of α-helix chains transporting through the pores, which can enrich our insights into and knowledge on biopolymers transporting through membranes.     

Some α-amino acids containing trifluoromethyl groups

Summary Ethanolamine was added to , -ditrifluoromethylacrylic ester and hexafluorovaline ester was hydroxyethylated. Both reactions yielded the ester of N-(-hydroxyethyl)-hexafluorovaline, which could be used as the starting material for the synthesis of physiologically active substances.     

Two supramolecular structures constructed from Keggin-type polyoxometalates and 4,4′-bipyridine

Two supramolecular compounds based on Keggin-type polyoxometalates (POMs), (4,4′-H₂bpy)(4,4′-Hbpy)[PMo₁₂O₄₀] (1) and (4,4′-H₂bpy)(4,4′-Hbpy)₂[SiW₁₂O₄₀]?·?4H₂O (2), have been synthesized hydrothermally and characterized by elemental analyses, IR, UV-Vis, XPS spectra, thermogravimetric analyses, and single-crystal X-ray diffraction analyses. The two compounds consist of 4,4′-bipyridine (4,4′-bpy) ligands and different Keggin-type POMs which are [PMo₁₂O₄₀]^3? for 1 and [SiW₁₂O₄₀]^4? for 2. There are hydrogen-bonding interactions between the POMs, 4,4′-bipyridine, and/or water in 1 and 2. In addition, 2 contains an uncommon (H₂O)₂ water cluster.     

Two new compounds from the stem of Vernonia cumingiana

Two new compounds vemonioside S and vemoniether S were isolated from the stem of Vernonia cumingiana, and their structures were elucidated on the basis of spectroscopic evidences.     

Novel aqueous phase supramolecular synthesis of α-oxindole-α-hydroxyphosphonates

α¹-Oxindole-α-hydroxyphosphonates were synthesized for the first time in water under neutral conditions mediated by β-cyclodextrin in high yields. The β-cyclodextrin can be recovered and reused without any loss of activity.     

Two new 5α-adynerin-type compounds from Parepigynum funingense

<正>A new 5α-adynerin-type cardenolide,named funingenoside U(1),together with its aglycone,(17R)-3β-hydroxy-4β-acetoxy-8, 14β-epoxy-5α-card-20(22)-enolide,was isolated from the roots of Parepigynumfuningense.Their structures were established on the basis of spectral(MS,1D and 2D NMR) measurements and chemical evidences.