Four New Podocarpane‐Type Trinorditerpenes from Aleurites moluccana

Four new podocarpane‐type trinorditerpenenes, (5β,10α)‐12,13‐dihydroxypodocarpa‐8,11,13‐trien‐3‐one ( 1 ), (5β,10α)‐12‐hydroxy‐13‐methoxypodocarpa‐8,11,13‐trien‐3‐one ( 2 ), (5β,10α)‐13‐hydroxy‐12‐methoxypodocarpa‐8,11,13‐trien‐3‐one ( 3 ), and (3α,5β,10α)‐13‐methoxypodocarpa‐8,11,13‐triene‐3,12‐diol ( 4 ), together with four known diterpenes, 12‐hydroxy‐13‐methylpodocarpa‐8,11,13‐trien‐3‐one ( 5 ), spruceanol ( 6 ), ent‐3α‐hydroxypimara‐8(14),15‐dien‐12‐one ( 7 ), and ent‐3β,14α‐hydroxypimara‐7,9(11),15‐triene‐12‐one ( 8 ), were isolated from the twigs and leaves of Aleurites moluccana. Their structures were elucidated by means of comprehensive spectroscopic analyses, including NMR and MS. Except 8 , all compounds were evaluated for their cytotoxicity; compound 4 exhibited moderate inhibitory activity against Raji cells with an IC₅₀ value of 4.24 μg/ml.     

Poly（meta-phenylene） Derivative with Rigid Twisted Biphenyl Units in Backbone： Synthesis, Structural Characterization, Photophysical Properties and Electroluminescence

A soluble poly(meta-phenylene)derivative with rigid twisted biphenyl unit was synthesized by the Yamamoto coupling reaction.The polymer is soluble in common organic solvents,and the number-average molecular weight is about 6500.The UV-Vis and quantum chemical calculation indicate that the different conformation segments named "conformers" exist in the polymer backbones;it was also further confirmed by the single crystal X-ray diffraction study of the dimeric model compound.The π-π transition of biphenyl segments of twisted and planar conformations made the polymer exhibit a strong absorption around 256 nm and a weak absorption at about 300 nm.Furthermore,the polymer exhibits a strong UV photoluminescence at 372 nm when the excitation wavelengths are longer than 300 nm.The ultraviolet-emitting electroluminescence(EL)device with the single layer structure shows EL λmax of the derivative at 370 nm.     

Surmounting tumor resistance to metallodrugs by co-loading a metal complex and siRNA in nanoparticles

Copper complexes are promising anticancer agents widely studied to overcome tumor resistance to metal-based anticancer drugs. Nevertheless, copper complexes per se encounter drug resistance from time to time. Adenosine-5′-triphosphate (ATP)-responsive nanoparticles containing a copper complex CTND and B-cell lymphoma 2 (Bcl-2) small interfering RNA (siRNA) were constructed to cope with the resistance of cancer cells to the complex. CTND and siRNA can be released from the nanoparticles in cancer cells upon reacting with intracellular ATP. The resistance of B16F10 melanoma cells to CTND was terminated by silencing the cellular Bcl-2 gene via RNA interference, and the therapeutic efficacy was significantly enhanced. The nanoparticles triggered a cellular autophagy that amplified the apoptotic signals, thus revealing a novel mechanism for antagonizing the resistance of copper complexes. In view of the extensive association of Bcl-2 protein with cancer resistance to chemotherapeutics, this strategy may be universally applicable for overcoming the ubiquitous drug resistance to metallodrugs.

Bcl-2-related tumor resistance to anticancer drugs can be overcome by silencing the cellular Bcl-2 gene via RNA interference. The realization of the goal is exemplified by delivering Bcl-2 siRNA and a tumor-resistant Cu complex to cancer cells with an ATP-responsive nanocarrier.     

Itosides A – I,New Phenolic Glycosides from Itoa orientalis

Eight new benzoylated gentisyl alcohol (=2‐(hydroxymethyl)benzene‐1,4‐diol) glucosides, itosides A–H ( 1 – 8 ), together with the new pyrocatechol (=benzene‐1,2‐diol) glycoside itoside I ( 9 ) were isolated from the bark and twigs of Itoa orientalis (Flacourtiaceae). In itosides B–D ( 2 – 4 ), the gentisyl alcohol moiety was esterified by 1‐hydroxy‐6‐oxocyclohex‐2‐ene‐1‐carboxylic acid, while itosides E–H ( 5 – 8 ) contained instead an additional 2‐hydroxybenzoic acid moiety. The compounds were accompanied by the known derivatives 4‐hydroxytremulacin ( 10 ), poliothyrsoside ( 11 ), poliothyrsin ( 12 ), homaloside D ( 13 ), tremulacin, and pyrocatechol β‐D ‐glucopyranoside. The structures of the new compounds were elucidated by spectral and chemical methods.     

Improved method for the determination of sulfur components in natural gas

Determination of trace concentrations of sulfur components in natural gas is a true analytical challenge. Only analytical procedures based on gas chromatography can meet the sensitivity and accuracy requirements dictated by environmental regulation institutions and modern chemical industry. In the present contribution the sample pretreatment and chromatographic separation steps have been evaluated and optimized based on the use of a flamebased sulfur chemiluminescence detector (SCD) for target compound detection. The proposed instrument consists of a programmed temperature vaporizing (PTV) injector employing a liner packed with Chromosorb 104, a 4 μm thick film apolar column and a flame-based SCD. Using a 13 mL sample loop the detection limit achievable with the new method is 3 μg S/m³. The precision of replicate measure. ments is generally in the range of 5–15% relative standard deviation. Lower detection limits can be achieved by preconcentrating larger sample volumes, e.g. 100 mL.     

Synthesis of （2R,4R）—2—N—tert—Butyloxycarbonyl Amino—4,5—epoxido—valeric Acid Methyl Ester

The stereoselective synthesis of (2R,4R)-2-N-tert-butyloxycarbonyl amino-4,5-epoxido-valeric acid methyl ester 8,which is the key intermediate for the synthesis of (2′S,2R)-3-trans-nitrocyclopropyl-alanine,was first accomplished.     

Atom-surface elastic scattering in the presence of laser radiation

A qualitative discussion on atom-surface elastic scattering taking place in the presence of laser radiation is given. It is suggested that appreciable effects of laser radiation on diffraction patterns may be expected if the laser radiation is capable of inducing electronic transitions in atoms with a large probability.Research sponsored by the Air Force Office of Scientific Research (AFSC), United States Air Force, under Contract No. F49620-78-C-0005, and the National Science Foundation under Grant No. CHE77-27826. The United States Government is authorized to reproduce and distribute reprints for governmental purposes notwithstanding any copyright notation hereon.Alfred P. Sloan Research Fellow, 1976–1980; Camille and Henry Dreyfus Teacher-Scholar, 1975–1980.     

Using three major criteria to evaluate aromaticity of five-member C-containing rings and their Si-, N-, and P-substituted aromatic heterocyclics

In this paper, we used bond-length equalization, aromatic stabilization energies (ASE) and nucleus-independent chemical shifts (NICS), calculated with (density functional theory) B3LYP levels at the 6-311+G^** basis set, to evaluate the aromaticity of a set of 38 five-member planar π-electron aromatic systems: sila-, aza- and phospha- derivatives and their parent systems. The result revealed statistically significant correlations among the above three criteria, and the order of aromaticity of the whole set was: Aza- derivatives rings > Phospha- derivatives rings > Sila- derivatives rings > Carbon-containing rings; NICS(0.6) and NICS(0.8) had the same results in evaluating the order of aromaticity in our case.     

Potential-energy surface for the electronic ground state of NH3 up to 20,000 cm-1 above equilibrium

Ab initio coupled cluster calculations with single and double substitutions and a perturbative treatment of connected triple excitations [CCSD(T)] with the augmented correlation-consistent polarized valence triple-zeta aug-cc-pVTZ basis at 51 816 geometries provide a six-dimensional potential-energy surface for the electronic ground state of NH3. At 3814 selected geometries, CBS+ energies are obtained by extrapolating the CCSD(T) results for the aug-cc-pVXZ(X=T,Q,5) basis sets to the complete basis set (CBS) limit and adding corrections for core-valence correlation and relativistic effects. CBS** ab initio energies are generated at 51,816 geometries by an empirical extrapolation of the CCSD(T)/aug-cc-pVTZ results to the CBS+ limit. They cover the energy region up to 20,000 cm-1 above equilibrium. Parametrized analytical functions are fitted through the ab initio points. For these analytical surfaces, vibrational term values and transition moments are calculated by means of a variational program employing a kinetic-energy operator expressed in the Eckart-Sayvetz frame. Comparisons against experiment are used to assess the quality of the generated potential-energy surfaces. A "spectroscopic" potential-energy surface of NH3 is determined by a slight empirical adjustment of the ab initio potential to the experimental vibrational term values. Variational calculations on this refined surface yield rms deviations from experiment of 0.8 cm-1 for 24 inversion splittings and 0.4 (3.0) cm-1 for 34 (51) vibrational term values up to 6100 (10,300) cm-1.     

无机盐对正负表面活性剂混合体系性质的影响

用滴体积法测定了四种离子强度下(μ=0.02, 0.05, 0.1, 0.2 mol·kg~(-1), 支持电解质为NaBr)C_(12)H_(25)SO_4Na/C_6H_(13)(NC_5H_5)Br混合体系在五种比例(10:1, 3:1, 1:1, 1:3, 1:10)时的临界胶团活度cma(25 ℃). 提出了无机盐对正负表面活性剂混合体系临界胶团活度的影响程度的计算式.