Tetra‐μ‐acetato‐κ2O:O′‐bis[(4‐phenylpyridine‐κN)copper(II)]

The title compound, [Cu₂(C₂H₃O₂)₄(C₁₁H₉N)₂] or [Cu₂(MeCO₂)₄(phpy)₂] (phpy is 4‐phenyl­pyridine), consists of centrosymmetric dimers in which the Cu^II atoms display a square‐pyramidal CuO₄N coordination, with four acetate O atoms in the basal plane [Cu—O 1.975 (3)–1.987 (3) Å] and the phpy N atom in the apical position [Cu—N 2.150 (3) Å]. The Cu atoms are 2.654 (1) Å apart and are bridged by four acetate groups. The discrete dimers are extended into a three‐dimensional supramolecular array through intermolecular π–π‐stacking interactions.     

Recognition of single nucleotide polymorphisms using scanning potential hairpin denaturation

Conventional single nucleotide polymorphism (SNP) assays, which based their detection on the stringency or temperature of the washing buffers, have encountered difficulties to distinguish a single base pair mismatch from a perfect match. In this study, scanning potential hairpin denaturation (SPHD) has been developed to detect SNP in a sensitive and reliable manner. Combined with hairpin oligonucleotide probes, scanning surface electric potential was used to induce a dissociation of double-stranded DNA around a unique "melting potential" (Vm), and it generated a high-contrast SNP recognition signal. A 21 base pair p53 gene segment was used to test this novel method. A single nucleotide mismatch to the hairpin probes caused an average of 400-800 mV difference in melting potential against the perfect match, while the error of this assay was lower than 20 mV. Experiments demonstrated that the hairpin stem was critical to the method. The concept of scanning potential hairpin denaturation could also be used extensively in different areas of nucleotide hybridization based assays.     

Copper-catalyzed cross-coupling of sulfonamides with aryl iodides and bromides facilitated by amino acid ligands

A highly general, convenient, and inexpensive catalyst system was developed for the N-arylation of sulfonamides with aryl iodides or bromides by using 5-20 mol % of CuI as catalyst, 20 mol % of N-methylglycine (for aryl iodides) or N,N-dimethylglycine (for aryl bromides) as ligand, and K₃PO₄ as base.     

分散聚合水基聚苯胺乳胶微球制备与表征

水溶性空间稳定剂聚乙烯吡咯烷酮（PVP）存在时，采用分散聚合制备水溶性单分散的聚苯胺(PAn)乳胶粒子，采用透射电子显微镜（TEM）观察粒子形态及尺寸；利用紫外-可见吸收光谱对胶体分散体系进行表征.实验结果表明，当PAn含量较少（w< 16.78％）时， PAn-PVP复合乳胶粒子呈米粒状；当PAn含量较大（w >23.22％）时， PAn-PVP复合乳胶粒子呈球形.     

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.     

Diterpenoids of Isodon macrophylla

Two new ent‐abietane diterpenoids, macrophynin E ( 1 ) and macrophynin F ( 2 ), and a known related ent‐abietanoid (?)‐lambertic acid ( 3 ), together with four known ent‐kauranoids, were isolated from the roots and aerial parts of Isodon macrophylla, respectively. The structures of the new compounds were elucidated on the basis of spectroscopic‐data analysis and chemical correlations.     

Tocopherols and Triterpenoids from Sida acuta

A new tocopherol derivative, 7_a‐methoxy‐α‐tocopherol ( 1 ), and a new taraxastane triterpene, taraxast‐1,20(30)‐dien‐3‐one ( 5 ), together with four known compounds, β‐tocopherol ( 2 ), α‐tocopherol ( 3 ), α‐tocospiro B ( 4 ) and taraxasterone ( 6 ) were isolated from the whole plant of Sida acuta. Their structures were elucidated by spectral analysis including MS, 1D and 2D‐NMR spectroscopy. Among those compounds, compounds 1 , 2 , and 3 showed significant antioxidant effect (EC₅₀ = 86.9, 68.2, and 70.9 μM, respectively) in the DPPH radicals scavenging activity assay.     

Scanning tunneling microscopy of prochiral anthracene derivatives on graphite: chain length effects on monolayer morphology

The morphology of monolayers formed upon adsorption of prochiral 1,5-substituted anthracene derivatives on highly oriented pyrolytic graphite is investigated using scanning tunneling microscopy at the liquid-solid interface. The adsorption orientation of these prochiral anthracene derivatives positions one of their enantiotopic faces in contact with the graphite. The molecules adsorb in rows with contact between adjacent anthracenes. The anthracene side chains extend perpendicular to the direction of the row repeat. All molecules within a single row adsorb via the same enantiotopic face. Anthracenes with side chains containing an even number of non-hydrogenic atoms (C, S) form monolayers in which molecules in adjacent rows adsorb via opposite enantiotopic faces. Anthracenes with side chains that contain an odd number of non-hydrogenic atoms form two-dimensional chiral domains in which all rows contain molecules adsorbed via the same enantiotopic face. This chain length effect on monolayer morphology represents a generalized example of structural effects previously observed in alkanoic acid monolayers formed on HOPG. The variation of the STM current with position in the vicinity of the anthracenes indicates that the highest occupied molecular orbital is the predominant mediator of tunneling for the aromatic group.     

The role of salt on cellulose dissolution in ethylene diamine/salt solvent systems

Ethylene diamine (EDA)/salt solvent systems can dissolve cellulose without any pretreatment. A comparison of the electrical conductivity of different salts in EDA was made at 25 °C, and conductivity decreased in the order of KSCN>KI>NaSCN at the same molar concentration. Among the salts tested, potassium thiocyanate (KSCN) was capable of dissolving both high molecular weight (DP>1000) and low molecular weight (DP = 210) cellulose, and this was confirmed by polarized light microscopy. ³⁹K and ¹⁴N NMR experiments were conducted at 70 °C as a function of cellobiose concentration with EDA/KSCN as the solvent. The results showed that the K⁺ ion interacts with cellobiose more than the SCN⁻ ion does. Recovered cellulose was studied by infrared spectroscopy (FTIR) and wide angle X-ray diffraction (WAXD). Changes in the FTIR absorption bands at 1,430 and 1,317 cm⁻¹ were associated with a change in the conformation of the C-6CH₂OH group. The changes in positions and/or intensities of absorption bands at 2,900, 1,163, and 8,97cm⁻¹ were related to the breaking of hydrogen bonds in cellulose. X-ray diffraction studies revealed that cellulose, recovered by precipitating cellulose solutions with water, underwent a polymorphic transformation from cellulose I to cellulose II.     

Electrophilic monofluoromethylation of O-, S-, and N-nucleophiles with chlorofluoromethane

CH₂ClF has been found to be a useful electrophilic monofluoromethylating agent for a variety of O-, S-, and N-nucleophiles. The reaction is not sensitive to the radical scavenger such as nitrobenzene, which strongly supports an S_N2 mechanism rather than an SET mechanism. Although most of these products (fluoromethyl ethers, sulfides, and amines) can be isolated with good purity, some of these compounds do intend to decompose (via defluorination) during storage. The electrophilic monofluoromethylation of carbon-nucleophiles was attempted with CH₂ClF, CH₂FI, or FCH₂OTs as monofluoromethylating agents, but with no success.