四（对叔丁基）硫杂杯[4]芳烃选择性包合四氟硼酸分子：晶体结构和理论研究

X－射线晶体衍射测定了4－(对叔丁基)硫杂杯[4]芳烃选择性地包合四氟硼酸分子。晶体学数据为：C₄₀H₄₉O₄S₄BF₄,M_r=808.88, 四方锥, 空间群 P4/nmm,a=1.5887(2), b=1.5887(2),c=0.8428(0) nm, V=2.127(2) nm³, Z=2,D_c=1.263 g·cm^-3,R₁=0.0405, _WR[I>2σ(I)]=0.1218. ¹⁹FNMR谱中,在-151.4 ppm处出现的峰,证实了四氟硼酸的存在。用Bader的分子中的原子理论方法计算了分子结构中的非共价键相互作用。结果显示,在四氟硼酸包合物中,除了F…H－C氢键作用和阳离子－阴离子的静电作用外,F^δ--C^δ+静电作用的存在也对4－(对叔丁基)硫杂杯[4]芳烃憎水空腔包合氟硼酸分子起到了稳定作用。     

Pharmaceutical microcalorimetry: recent advances in the study of solid state materials

This paper discusses the theory and experimental application of microcalorimetry to the study of solid state reactions of pharmaceutical importance. The practical example selected is that of formulated products containing benzoyl peroxide – a treatment for acne and athlete’s foot. A newly developed procedure for data analysis is outlined and preliminary results from chemometric-based analysis of complex solid state reaction schemes is presented. Finally, the microcalorimetric requirements for such stability studies are contrasted with the newly emerging multi-channel “chip calorimeters” that operate in the nano range (watts, material, concentration) with high throughput potential.     

Principal components of phenolics to characterize red Vinho Verde grapes: Anthocyanins or non-coloured compounds?

Phenolic profile of 10 different varieties of red “Vinho Verde” grapes (Azal Tinto, Borraçal, Brancelho, Doçal, Espadeiro, Padeiro de Basto, Pedral, Rabo de ovelha, Verdelho and Vinhão), from Minho (Portugal) were studied. Nine Flavonols, four phenolic acids, three flavan-3-ols, one stilben and eight anthocyanins were determined. Malvidin-3-O-glucoside was the most abundant anthocyanin while the main non-coloured compound was much more heterogeneous: catechin, epicatechin, myricetin-3-O-glucoside, quercetin-3-O-glucoside or syringetin-3-O-glucoside. Anthocyanin contents ranged from 42 to 97%. Principal component analysis (PCA) was applied to analyse the date and study the relations between the samples and their phenolic profiles. Anthocyanin profile proved to be a good marker to characterize the varieties even considering different origin and harvest. “Vinhão” grapes showed anthocyanins levels until twenty four times higher than the rest of the samples, with 97% of these compounds.     

Effects of poly (ethylene glycol) chains conformational transition on the properties of mixed DMPC/DMPE-PEG thin liquid films and monolayers

Foam thin liquid films (TLF) and monolayers at the air–water interface formed by DMPC mixed with DMPE-bonded poly (ethylene glycol)s (DMPE-PEG₅₅₀, DMPE-PEG₂₀₀₀ and DMPE-PEG₅₀₀₀) were obtained. The influence of both (i) PEG chain size (evaluated in terms of Mw) and mushroom-to-brush conformational transition and (ii) of the liposome/micelle ratio in the film-forming dispersions, on the interfacial properties of mixed DMPC/DMPE-PEG films was compared.

Foam film studies demonstrated that DMPE-PEG addition to foam TLFs caused (i) delayed kinetics of film thinning and black spot expansion and (ii) film stabilization. At the mushroom-to-brush transition, due to steric repulsion increased DMPE-PEG films thickness reached 25 nm while pure DMPC films were only 8 nm thick Newton black films. It was possible to differentiate DMPE-PEG_2000/5000 from DMPE-PEG₅₅₀ by the ability to change foam TLF formation mechanism, which could be of great importance for “stealth” liposome design.

Monolayer studies showed improved formation kinetics and equilibrium surface tension decrease for DMPE-PEG monolayers compared with DMPC pure films.

SEM observations revealed “smoothing” and “sealing” of the defects in the solid-supported layer surface by DMPE-PEGs adsorption, which could explain DMPE-PEGs ability to stabilize TLFs and to decrease monolayer surface tension.

All effects in monolayers, foam TLFs and solid-supported layers increased with the increase of PEG Mw and DMPE-PEG concentration. However, at the critical DMPE-PEG concentration (where mushroom-to-brush conformational transition occurred) maximal magnitude of the effects was reached, which only slightly changed at further DMPE-PEG content and micelle/liposome ratio increase.     

A comparative post-Hartree–Fock and density functional theory study of monochalcogenide diatomic molecules

HOMO and LUMO (FMOs) play important role in the optical properties of meridianal isomer of tris(8-hydroxyquinolino)aluminum (mer-Alq3) and its derivatives. The frontier molecular orbitals (FMOs) also play a vital role in the process of charge transport. It is urgent to find the reason of FMO distribution pattern among the ligands. The structures of mer-Alq3 and its “CH”/N substituted derivatives have been optimized at the B3LYP/6-31G^* level. Energy decomposition analysis has been performed at the B3LYP/DZP level. The results of energy-partitioning analysis of ground states are discussed. It has been explained that HOMOs are on A-ligands due to weaker electrostatic interaction energy between L_a-AlL_bL_c fragments while LUMOs are on B-ligands due to weaker orbital interaction energy between L_b-AlL_aL_c fragments.     

A two-step supercritical fluid extraction of polycyclic aromatic hydrocarbons from roadside soil samples

A two-step procedure for the supercritical fluid extraction (SFE) of polycyclic aromatic hydrocarbons from soil samples was developed. The procedure consists of a static supercritical fluid treatment in a closed extraction cell at a high temperature (T=250 or 340degreesC for 20 min) and an SFE with a solvent trapping. During the static phase, the sample is exposed to a supercritical organic solvent (methanol, toluene, dichloromethane, ACN, acetone, and hexane). The solvent penetrates particles of the matrix to substitute strongly bonded molecules and dissolves the analytes in the supercritical phase. At ambient temperature, supercritical fluids became liquid and lost their solvation abilities. Most of the analytes condense on the surface of the particles or on the extraction cell walls without forming strong bonds or penetrating deep into the matrix. Thus, the pretreatment liberates the analytes and they behave similar to those in freshly spiked samples. The common SFE with toluene-modified CO2 as an extraction fluid follows the static phase. With the use of the most suitable extraction phases (toluene, ACN), the extraction efficiency of the combined procedure is much higher (approximately100%). The results of the combined procedure are compared to the SFE procedure of the same untreated sample (difference less than 5%) and to the Soxhlet extraction. The extracts were analyzed using a GC with the flame ionization detection.     

Synthesis of new 1<Emphasis Type="Italic">H</Emphasis>-pyridazine derivatives <Emphasis Type="Italic">peri</Emphasis>-annelated with acenaphthene and acenaphthylene

The reaction of 6-acetyl-5-hydroxyacenaphthene with methylhydrazine afforded 1,3-dimethyl-1H-6,7-dihydroacenaphtho[5,6-de]pyridazine. Its dehydrogenation with chloranil gave 1,3-dimethyl-1H-acenaphtho[5,6-de]pyridazine, which is a heteroaromatic compound with an essentially new topology of the ρsystem. The reaction of 3-methyl-1H-6,7-dihydroacenaphtho[5,6-de]pyridazine with 3,5-di-tert-butyl-1,2-benzoquinone yielded a dimer containing the acenaphthene and acenaphthylene moieties of peri-annelated 1H-1,2-diazines connected in positions 1′ and 9.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 777–780, March, 2005.     

Selective Alkaline Protease Catalyzed Hydrolysis of Peptide Esters

Procedures for preparing C-terminal free peptides from hydrolysis of its corresponding methyl or benzyl esters catalyzed by alkaline protease has been developed. N-protected peptides having side-chain ester protecting groups or successive hydrophobic amino acid residues in its sequence are hydrolyzed selectively at C-terminal only and leave other bonds (β and γ- ester or peptide bonds) intact. Compounds which cause a side reaction in base mediated saponification could be hydrolyzed safely by this procedure. Products of this hydrolysis are useful intermediates for fragments coupling in the solid phase peptide synthesis.