Novel temperature‐responsive water‐soluble copolymers based on 2‐hydroxyethylacrylate and vinyl butyl ether and their interactions with poly(carboxylic acids)

Novel water‐soluble amphiphilic copolymers have been synthesized by free radical copolymerization of 2‐hydroxyethylacrylate with vinyl butyl ether. In water these copolymers exhibit lower critical solution temperature, which depends on the content of hydrophobic vinyl butyl ether units. The interaction between these copolymers and poly(acrylic acid) or poly(methacrylic acid) in aqueous solutions results in formation of interpolymer complexes stabilized by hydrogen bonds and hydrophobic interactions. An increase in hydrophobicity of the copolymers leads to the enhancement of their complex formation ability with respect to poly(acrylic acid) and poly(methacrylic acid). Poly(methacrylic acid) forms stronger complexes with the copolymers when compared with poly(acrylic acid). The complexes exhibit dual sensitivity to pH‐ and temperature and this property may be easily adjusted regulating the strength of interaction. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 195–204, 2006     

Electronic Excitation of [(μ4‐η2‐alkyne)Rh4(CO)8(μ‐CO)2]: An In Situ UV/Vis Spectroscopy,Spectral Reconstruction and DFT Study

Reactions of three alkynes, namely, 1‐heptyne, 3‐hexyne and 1‐phenyl‐1‐butyne, with [Rh₄(CO)₉(μ‐CO)₃] are performed in anhydrous hexane under argon atmosphere with multiple perturbations of alkynes and [Rh₄(CO)₉(μ‐CO)₃]. The reactions are monitored by in situ UV/Vis spectroscopy, and the collected electronic spectra are further analyzed with the band‐target entropy minimization (BTEM) family of algorithms to reconstruct the pure component spectra. Three BTEM estimates of [(μ₄‐η²‐alkyne)Rh₄(CO)₈(μ‐CO)₂], in addition to that of [Rh₄(CO)₉(μ‐CO)₃], are successfully reconstructed from the experimental spectra. Time‐dependent density functional theory (TD‐DFT) predicted spectra at the PBE0/DGDZVP level are consistent with the corresponding BTEM estimates. The present study demonstrates that: 1) the BTEM family of algorithms is successful in analyzing multi‐component UV/Vis spectra and results in good spectral estimates of the trace organometallics present; and 2) the subsequent DFT/TD‐DFT methods provide an interpretation of the nature of the electronic excitation and can be used to predict the electronic spectra of similar transition organometallic complexes.     

Self-assembling systems based on amphiphilic alkyltriphenylphosphonium bromides: elucidation of the role of head group

A systematic study of the aggregation behavior of alkyltriphenylphosphonium bromides (TPPB-n; n=8, 10, 12, 14, 16, 18; here n is the number of carbon atoms in alkyl groups) in aqueous solutions has been carried out and compared with trimethyl ammonium bromides (TMAB-n). Critical micelle concentrations (cmcs) of TPPB-n and TMAB-n decrease with the number of carbon atoms with the slope parameter of ca.0.3. The low cmcs and effective solubilization power toward Orange OT indicate high micellization capacity of phosphonium surfactants. The low counterion binding parameter β is revealed for TPPB-10 and TPPB-12, while high counterion binding of ≥80% is observed for high TPPB-n homologs. Values of the surface potential ψ calculated on the basis of pK(a) shifts of p-nitrophenols is similar for both series and monotonously increase with alkyl chain length. Several points indicate non-monotonic changes within TPPB-n series. There are peculiarities of the tensiometry and solubilization plots for high homologs and above mentioned increases in counterion binding on transiting from low to high molecular weight surfactants. Differences in aggregation behavior between TPPB and TMAB series and between low and high homologs can be due to the specific structural character of the TPP(+) cation, which is supported by X-ray data.     

Last ten years (2008–2018) of chiral ligand‐exchange chromatography in HPLC: An updated review

Chiral ligand‐exchange chromatography is one of the elective strategies for the direct enantioresolution of small chelating compounds: amino acids, diamines, amino alcohols, diols, small peptides, etc. Unlike other methods, the interaction between chiral selector and analyte enantiomers is mediated by a cation, thus producing diastereomeric ternary complexes. Two main approaches are conventionally applied in chiral ligand‐exchange chromatography. The first relies upon chiral stationary phases where the chiral selector is either covalently immobilized or physically adsorbed onto suitable packing materials (coated phases). In the second approach, chiral molecules are added to the eluent, thus generating chiral eluent systems. Among the advantages of chiral ligand‐exchange chromatography, the generation of UV/vis‐active metal complexes, and the use of commercially available or easy‐to‐synthesize chiral selectors, in combination to rather inexpensive achiral columns for coated phases and chiral eluents, are noteworthy. Besides amino acids and amino alcohols, other species have proven suitable for chiral ligand‐exchange chromatography applications. Recently, the use of either chiral ionic liquids or micellar liquid chromatography systems as well as the successful off‐column formation of diastereomeric complexes have expanded the selectivity profiles and application fields. All of these issues are touched in the review, shedding light to the contributions appeared in the last decade.     

Structure-activity studies of irumamycin type macrolides from Streptomyces sp. INA-Ac-5812

Three natural glycosylated macrolide compounds, known irumamycin 1 and X-14952B 2, as well as new isoirumamycin 3, were isolated from ethyl acetate mycelium extract of Streptomyces sp. INA-Ac-5812. Structures of the compounds were elucidated using 1D and 2D NMR. Isoirumamycin 3 was found to be an isomer of irumamycin with an 18-membered macrolactone ring instead of 20-membered macrolide in irumamycin. A previously unknown stereo configuration of irumamycin epoxide (C23, C24) and hemiketal (C3, C7) fragments was deduced from NMR data (ROESY/NOESY and HSQMBC). Cytotoxic, antifungal and antibacterial activities were studied for all isolated compounds. Comparison of the collected data showed crucial importance of 20-membered macrolactone ring for antimicrobial properties of this antibiotic family.     

The Phenolic Compounds Profile and Cosmeceutical Significance of Two Kazakh Species of Onions: Allium galanthum and A. turkestanicum

Numerous species of Allium genus have been used in the traditional medicine based on their vast biological effects, e.g., antimicrobial, digestion stimulant, anti-sclerotic, soothing, antiradical or wound healing properties. In this work, unpolar and polar extracts from two lesser-investigated species of Allium growing in Kazakhstan, Allium galanthum Kar. & Kir. (AG) and A. turkestanicum Regel. (AT), were studied for their composition and biological effects. In the HPLC-ESI-QTOF-MS/MS analyses of water and alcoholic extracts simple organic acids, flavonoids and their glycosides were found to be the best represented group of secondary metabolites. On the other hand, in the GC-MS analysis diethyl ether, extracts were found to be rich sources of straight-chain hydrocarbons and their alcohols, fatty acids and sterols. The antimicrobial activity assessment showed a lower activity of polar extracts, however, the diethyl ether extract from AT bulbs and AG chives showed the strongest activity against Bacillus subtilis ATCC 6633, B. cereus ATCC 10876, some species of Staphylococcus (S. aureus ATCC 25923 and S. epidermidis ATCC 12228) and all tested Candida species (Candida albicans ATCC 2091, Candida albicans ATCC 10231, Candida glabrata ATCC 90030, Candida krusei ATCC 14243 and Candida parapsilosis ATCC 22019) with a minimum inhibitory concentration of 0.125–0.5 mg/mL. The highest antiradical capacity exhibited diethyl ether extracts from AG bulbs (IC50 = 19274.78 ± 92.11 mg Trolox eq/g of dried extract) in DPPH assay. In ABTS scavenging assay, the highest value of mg Trolox equivalents, 50.85 ± 2.90 was calculated for diethyl ether extract from AT bulbs. The same extract showed the highest inhibition of mushroom tyrosinase (82.65 ± 1.28% of enzyme activity), whereas AG bulb ether extract was the most efficient murine tyrosinase inhibitor (54% of the enzyme activity). The performed tests confirm possible cosmeceutical applications of these plants.     

Properties of propoxy-derivatives based on the acidic fraction of coconut oil

Hydrolysis of coconut oil was carried out with alkali, and acid fraction was separated. The obtained acid fraction was propoxylated with propylene oxide at 1:1, 1:3, 1:5, and 1:7 molar ratios and 140?150°C. Physico-chemical as well as surface activity parameters of these propoxylates have been determined. Petroleum-collecting and petroleum-dispersing properties of the propoxylates have been studied on thin oil slick on the surface of water with varying degrees of mineralization. The influence of various factors (petroleum layer thickness, the water salinity, and the nature of petroleum) on petroleum-collecting and petroleum-dispersing properties was studied.     

Bisaryldithiophosphonic Acids: Synthesis and Their Reactions with Organyl Chlorosilanes,Germanes, Stannanes,and Plumbanes

A method of synthesizing arylbisdithiophosphonic acids was developed by the reaction of 2,4-diaryl 1,3,2,4-dithiadiphosphetane-2,4-disulfides with tri(ethylene glycol) and 1,4-butandiol in anhydrous benzene suspension under mild conditions. The arylbisdithiophosphonic acids thus obtained were transformed into the corresponding diammonium salts. New bis(triorganylgermyl), stannyl and plumbyl, and cyclic diphenylsilyl and diphenylplumbyl derivatives of arylbisdithiophosphonic acids were prepared from the reactions of diammonium salts of the corresponding acids with triorganylchlorogermane, chlorostannane, chloroplumbane, diphenyldichlorosilane, and diphenyl dichloroplumbane.