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We have performed CID experiments on a triple quadrupole instrument, lowering the collision gas pressure by 50 times compared to its conventional value. The results show that at very low-collision gas pressure, single collisions dominate the spectra. Indirectly, these results suggest that under conventional conditions, 20–50 collisions may be typical in CID experiments. The results show a marked difference between low- and high-pressure CID spectra, the latter being characterized in terms of 'slow heating' and predominance of consecutive reactions. The results indicate that under single collision conditions, the collisional energy transfer efficiency is very high: nearly 100% of the center of mass kinetic energy is converted to internal energy. [ABSTRACT FROM AUTHOR]

Considerable acceleration was observed in the guanidine‐base catalysed Claisen‐Schmidt condensation of benzaldehyde and a 17α‐methyl‐18‐nor‐5α,13α‐androstan‐16‐one (1) in the presence of ethylene glycol. Rate‐enhancement effects of various alcohols and diols were compared. In quantum chemical calculations, coordination of the carbonyl group of the substrate was found to reduce the potential barrier to the proton transfer from the α carbon and thus facilitate the formation of the anion that attacks the aldehyde. Both the experiments and the calculations showed that diols enhance the reactivity more efficiently than alcohols. Ethylene glycol/guanidine‐base mixtures were found to be efficient catalysts and solvents in the synthesis of a range of new 17α‐methyl‐18‐nor‐13α‐15‐arylidene steroids. This solvent mixture has a further advantage: the crude products can be isolated by simple extraction after introduction of CO2. It is also shown that by the proper choice of the base, the base/diol mixture can be recycled. [ABSTRACT FROM AUTHOR]

In the catalytic addition of thiols to 16‐dehydropregnenolone fourteen thioethers were prepared via thiol‐Michael addition reaction in the presence of different aliphatic and aromatic thiols as reagents. [HDBU][OAc] was proved to be an efficient catalyst and solvent providing thioether derivatives in good to excellent yields. The ionic liquid could be reused for five times without noticeable loss of activity. The structures of compounds were confirmed by 1H‐, 13C NMR and IR spectroscopy and mass spectral analysis. A series of these pregnenolone derivatives were evaluated for their cytotoxic activity on breast cancer (MDA‐MB‐231, MCF7) cell lines. [ABSTRACT FROM AUTHOR]

Switchable polarity solvents (reversible ionic liquids) have been used to replace conventional catalysts and solvents in Claisen‐Schmidt condensation reactions of 16‐formyl steroids and aromatic ketones. The primarily formed α,β‐unsaturated ketones may undergo a Michael addition with the aromatic ketone reaction partner. By the proper choice of the reaction conditions, either the α,β‐unsaturated ketone or the products of the domino Claisen‐Schmidt condensation ‐ Michael addition could be obtained with good selectivity. The catalyst could successfully be recovered and reused. The steroidal products with androstane and estrane skeleton were characterized by different spectroscopic methods (NMR, IR, MS). [ABSTRACT FROM AUTHOR]

A H-shaped heterometallic Sn4Au4 system that displays tuneable guest-dependent optical and photoluminescent properties has been synthesized. It shows selective dye sorption, while its stimuli-responsive methylred-rich solid is sensitive towards pH variations. This non-emissive Sn4Au4 system exhibits multicolour luminescence in the presence of aniline derivatives. [ABSTRACT FROM AUTHOR]

Switchable polarity recyclable solvent mixtures were applied as reaction medium and catalyst to replace the conventional base catalysts in the Claisen–Schmidt condensation of 17‐oxo steroids with aromatic aldehydes. Reversibility between ionic and nonionic forms of the new 2‐n‐butyl‐1,1,3,3‐tetramethylguanidine (nBu‐TMG)/ethylene glycol/CO2 and 2‐tert‐butyl‐1,1,3,3‐tetramethylguanidine (tBu‐TMG)/ethylene glycol/CO2 systems were proved by conductivity measurements. The structure of the ionic form was established by 1H NMR and IR measurements and by quantum chemical calculations. The steroidal products with androstane and estrane skeleton were characterised with spectroscopic methods (NMR, IR, MS). [ABSTRACT FROM AUTHOR]

Rationale: Protein citrullination (deimination) is a post-translational modification of proteins converting arginine(s) into citrulline(s). "Overcitrullination" could be associated with severe pathological conditions. Mass spectrometric analysis of modified proteins is hindered by several problems. A comprehensive study of the fragmentation of deiminated peptides is not yet available. In this paper we have made an attempt to describe the characteristics of these processes, based on the studies of epitope model oligopeptides derived from clinically relevant proteins. Methods: Solutions of purified model peptides containing either one or two citrulline residues as well as their native variants were injected directly into the electrospray source of a high accuracy and resolution quadrupole-time-of-flight instrument and were analysed by tandem mass spectrometry using low-energy collision-induced dissociation. Results: Loss of isocyanic acid from citrulline residues is a preferred fragmentation route for deiminated peptides, which yields ornithine residues in the sequence. However, simultaneous detection of both the isocyanic acid loss and sequence fragments is often compromised. A preferential cleavage site was observed between citrulline and any other following amino acids yielding intensive complementary b- and y-type ions. Also, citrulline positioned at the C-termini displays a preferential cleavage N-terminal to this residue yielding characteristic y1 ions. These phenomena are described here for the first time and are referred to as the "citrulline effect". Conclusions: We found that the citrulline effect is very pronounced and could be used as a complementary tool for the confirmation of modification sites in addition to losses of isocyanic acids from the protonated molecules or from fragment ions. Low collision energy applied to peptide ions having partially mobile protons reveals the site of modification by generating specific and intensive fragments of the sequence. On the other hand, fragmenting precursor ions with mobile protons usually allows full sequence coverage, although citrulline-specific fragments may exhibit lower intensities compared to other fragments. [ABSTRACT FROM AUTHOR]

Heterogeneous copper catalysts were prepared by the deposition of CuI on a hybrid material consisting of silica and a polymer with imidazolium moieties. The solid materials were characterised using solid‐phase NMR, Fourier transform infrared, Raman and X‐ray photoelectron spectroscopies and Brunauer–Emmett–Teller measurements. The formation of copper–carbene complexes was proved from Raman spectra and the results were supported by density functional theory calculations. The catalyst could be recycled efficiently with low loss of copper. Metal leaching was proved to be facilitated by the use of conditions typical for a homogeneous system (the presence of a polar solvent or the addition of a tertiary amine). Besides simple model reactions, the best catalyst was found to be suitable for the synthesis of triazoles of more elaborate structure, such as ferrocene or steroid derivatives. [ABSTRACT FROM AUTHOR]

There is abundant literature regarding the symmetric α-dioximes, R’–C(=NOH)–C(=NOH)–R”, (R’=R”) and their derivatives. However, this is not the case for asymmetric α-dioximes, and the goal of this research was to increase knowledge in this domain. The thermal stability of the asymmetric α-dioximes and their Co-complexes is lower than that of the similar symmetric derivatives. This difference has also been observed in spectroscopical analysis. In this study, the synthesis of a series of Co complexes of the type [Co(Et-Me-DioxH)2L2]+, (L=amine) was described and characterized with thermoanalytical and spectroscopical methods. [ABSTRACT FROM AUTHOR]

Constitutive- and immunoproteasomes are part of the ubiquitin–proteasome system (UPS), which is responsible for the protein homeostasis. Selective inhibition of the immunoproteasome offers opportunities for the treatment of numerous diseases, including inflammation, autoimmune diseases, and hematologic malignancies. Although several inhibitors have been reported, selective nonpeptidic inhibitors are sparse. Here, we describe two series of compounds that target both proteasomes. First, benzoxazole-2-carbonitriles as fragment-sized covalent immunoproteasome inhibitors are reported. Systematic substituent scans around the fragment core of benzoxazole-2-carbonitrile led to compounds with single digit micromolar inhibition of the β5i subunit. Experimental and computational reactivity studies revealed that the substituents do not affect the covalent reactivity of the carbonitrile warhead, but mainly influence the non-covalent recognition. Considering the small size of the inhibitors, this finding emphasizes the importance of the non-covalent recognition step in the covalent mechanism of action. As a follow-up series, bidentate inhibitors are disclosed, in which electrophilic heterocyclic fragments, i.e., 2-vinylthiazole, benzoxazole-2-carbonitrile, and benzimidazole-2-carbonitrile were linked to threonine-targeting (R)-boroleucine moieties. These compounds were designed to bind both the Thr1 and β5i-subunit-specific residue Cys48. However, inhibitory activities against (immuno)proteasome subunits showed that bidentate compounds inhibit the β5, β5i, β1, and β1i subunits with submicromolar to low-micromolar IC50 values. Inhibitory assays against unrelated enzymes showed that compounds from both series are selective for proteasomes. The presented nonpeptidic and covalent derivatives are suitable hit compounds for the development of either β5i-selective immunoproteasome inhibitors or compounds targeting multiple subunits of both proteasomes. [ABSTRACT FROM AUTHOR]

During our screening studies, attractiveness of a ternary mixture of synthetic Grandlure I [racemic cis-1-methyl-2-(1-methylenethenyl)-cyclobutane ethanol], Grandlure II [( Z)-2-(3,3-dimethyl)cyclohexylidene ethanol], and Grandlure III–IV [( Z)- and ( E)-2-ochtodenal; ( Z)- and ( E)-(3,3-dimethyl)cyclohexylidene acetaldehyde] for the sugar-beet weevil, Bothynoderes punctiventris Germar (Coleoptera: Curculionidae), was observed in field-trapping tests at several sites in Hungary and Serbia. The mixture attracted both males and females. Later tests revealed that of the components in the ternary mixture, only Grandlure III–IV were responsible for attraction, and the addition of Grandlures I or II in varying percentages had no influence on trap captures. Traps baited with 50–50 000 µg of Grandlure III–IV on rubber or polyethylene dispensers yielded high catches of weevils. When testing synthetic samples enriched in the respective geometrical isomer, Grandlure IV had a tendency of catching more weevils, but differences were not significant from lower catches by a 1:1 Z: E blend or Grandlure III. In gas chromatography–flame ionization detection/electroantennographic detection studies, antennae of both female and male weevils were more responsive to the ( E)- than to the ( Z)-isomer suggesting a more important role for Grandlure IV. Efforts to verify the presence of Grandlure III or IV in volatiles collected from either sex of live sugar-beet weevils or body washings with pentane remained inconclusive. Traps baited with Grandlure III–IV can now be used as sensitive and powerful trapping tools in the control of the sugar-beet weevil. [ABSTRACT FROM AUTHOR]

Some approaches and examples are shown to demonstrate the usefulness of inherently 'classical' parameters, such as bond orders and valences derivable from quantum mechanical wavefunctions, in the description and prediction of mass spectral primary fragmentation processes. [ABSTRACT FROM AUTHOR]

Aza-Michael addition of 16-dehydropregnenolone was studied in the presence of a basic ionic liquid, [DBU][OAc] as catalyst and solvent. The reaction was carried out using different primary and secondary amines as N -nucleophiles. The products were obtained in moderate to good yields and were characterized by 1 H and 13 C NMR, MS and IR. The ionic liquid was found to be an efficient and recyclable catalyst that was reused five times. The products were investigated for the inhibition of in vitro C 17,20 -lyase activity and displayed moderate inhibitory effect. [ABSTRACT FROM AUTHOR]

Transesterification of fatty acid containing used or nonfood type vegetable oils with methanol in the presence of partially hydrated calcium oxide has been performed. The calcium soaps formed are treated with sulfuric acid without separation from the ester phase, and the free acids formed are immediately converted to ester with the excess of methanol and the sulfuric acid (as catalyst). [ABSTRACT FROM AUTHOR]