A mild hydrolysis of esters mediated by lithium salts

When treated with amine bases such as triethylamine and various lithium salts in wet solvents, esters are efficiently hydrolyzed to the corresponding acids in good yields. Esters incorporating an α- or β-heteroatom with respect to the ester carbonyl group are hydrolyzed rapidly even at room temperature. To further demonstrate the usefulness of this method, one example is provided where hydrolysis of acetylated camphorsultam is mediated by LiBr.     

Reactivity of diazoazoles and azolediazonium salts in <Emphasis Type="Italic">C</Emphasis>-azo coupling reactions

The comparative reactivity of heterocyclic diazo compounds and the corresponding diazonium salts in C-azo coupling reactions was studied using imidazole, pyrazole, and triazole derivatives as examples.The reactivities of pyrazole- and imidazole-derived diazonium salts are much lower than those of thiadiazole- and 1,2,4-triazole-derived diazonium salts but higher than those of pyrrole and indole diazo compounds.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 348–358, February, 2005.     

Hierarchical Functionalized Polymeric‐Ceramic Coatings on Mg‐Ca Alloys for Biodegradable Implant Applications

Magnesium‐based implants present several advantages for clinical applications, in particular due to their biocompatibility and degradability. However, degradation products can affect negatively the cell activity. In this work, a combined coating strategy to control the implant degradation and cell regulation processes is evaluated, including plasma electrolytic oxidation (PEO) that produces a 13 µm‐thick Ca, P, and Si containing ceramic coating with surface porosity, and breath figures (BF) approach that produces a porous polymeric poly(ε‐caprolactone) surface. The degradation of PCL‐PEO‐coated Mg hierarchical scaffold can be tailored to promote cell adhesion and proliferation into the porous structure. As a result, cell culture can colonize the inner PEO‐ceramic coating structure where higher amount of bioelements are present. The Mg/PEO/PCL/BF scaffolds exhibit equally good or better premyoblast cell adhesion and proliferation compared with Ti CP control. The biological behavior of this new hierarchical functionalized scaffold can improve the implantation success in bone and cardiovascular clinical applications.     

Metal-free synthesis of pyridin-2-yl ureas from 2-aminopyridinium salts

An unprecedented base promoted domino approach has been developed for the synthesis of pyridin-2-yl urea derivatives via the reaction of 2-aminopyridinium salts and arylamines. The developed strategy tolerated a wide range of functional groups and afforded pyridin-2-yl ureas in moderate to good yields. The reaction was postulated to involve tandem cyclization, intermolecular nucleophilic addition, ring opening, and demethylation.     

Mixed electrolytes in hydrophobic interaction chromatography†

An essential part of the modulation of protein‐binding capacity in hydrophobic interaction chromatography is the buffer‐salt system. Besides using “single” electrolytes, multicomponent electrolyte mixtures may be used as an additional tool. Both the protein solubility and the binding capacity depend on the position of a salt in the so‐called Hofmeister series. Specific interactions are observed for an individual protein‐salt combination. For salt mixtures, selectivity, recovery, and binding capacity do not behave like for the single salts that are positioned in between the two mixed components in the Hofmeister series, as the continuous correlation would suggest. Thus, finding strategies for mixed salts could potentially lead to improved capacities in hydrophobic interaction chromatography. Mixtures of ammonium sulfate, sodium citrate, sodium sulfate, sodium chloride, sodium acetate, and glycine were used to investigate the binding capacities for lysozyme and a monoclonal antibody on various hydrophobic resins. Resin capacity for two investigated proteins increases when mixtures consisting of a chaotropic and a kosmotropic salt are applied. It seems to be related to the rather basic isoelectric points of the proteins.     

Catalytic ring opening of acetylcyclopropane by water and alcohols under the action of copper or palladium salts

The possibility of the cleavage of the C—C bond in acetylcyclopropane (ACP) under the action of water or alcohols in the presence of copper or palladium salts was demonstrated for the first time. At 175—180 °C, the reactions proceeded regioselectively with the cleavage of the C(1)—C(2) bond in the cyclopropane ring. The reaction of ACP with water afforded 5-hydroxypentan-2-one, bis(3-acetylpropyl) ether, and furan compounds, whereas the reactions with alcohols proceeded selectively to form 5-alkoxypentan-2-ones. The yields of the latter depend on the nature and structure of the alcohol, the maximum values (98%) being achieved in the case of primary alcohols.     

Copper‐Catalyzed Enantioselective Arylative Desymmetrization of Prochiral Cyclopentenes with Diaryliodonium Salts

A copper‐catalyzed enantioselective arylative desymmetrization of prochiral cyclopentenes with diaryliodonium salts was developed. In the presence of a catalytic amount of a chiral copper–bisoxazoline complex, which was generated in situ, the reaction of 4‐substituted or 4,4‐disubstituted cyclopent‐1‐enes with diaryliodonium hexafluoroarsenates afforded the chiral arylated products in good yields with excellent enantioselectivity. A cyclohexyl‐containing Box ligand was essential for the high enantioselectivity. Transformation of the enantiomerically enriched adducts into other chiral building blocks is also documented.