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Twenty juvenile individuals of brown bullhead (Ameiurus nebulosus), average weight 77 g, were fed by abiraterone acetate prodrug dissolved in olive oil via gastric probe. Dose applied was 3 mg/10 g fish weight. After feeding, they were let out into aquarium and kept there for 3 days. Aquarium water containing excreted metabolites was extracted, and sample was purified and finally analyzed by means of HPLC/MS. Expected both primary (products of hydroxylation) and secondary (products of glucuronidation and sulfatation) metabolites of abiraterone acetate were identified. The NMR measurement of one of the prevailing metabolites presumed to be one of possible hydroxy-abiraterones discovered that it is not hydroxy-abiraterone but abiraterone 16,17-epoxide. Closer analysis of MS2 and MS3 spectra revealed that one of presumed hydroxy-abiraterone acetates and also some secondary metabolites are probably 16,17-epoxides.

Several families of 3,4-dimethylthiolane-based compounds spontaneously formed upon cutting of onion (Allium cepa) were studied. We report the isolation of the first known example of a naturally occ...

Within the growing community of Fourier transform mass spectrometry users, the identification of fine isotope structure has become an indispensable method for molecular formula determination. In this work, the fine isotope envelopes for accessing the mutual ratio of 2 closely related pyoverdines in a mixture were used. Bacterial siderophores pyoverdines D and E cannot be easily separated via liquid chromatography-mass spectrometry because their structures differ in (de)amidation at the respective chromophore parts only. Their mutual ratio was determined in a mixture via nuclear magnetic resonance spectroscopy and semiquantitative mass spectrometry using our open-source software CycloBranch, which represents a genuine free tool supporting the determination of fine isotope structures in both conventional and product ion mass spectra. Native Bruker, Thermo, and Waters data formats are supported in addition to XML and plain text formats.

The compounds responsible for the bitter off-taste of processed onion (Allium cepa) were studied. Using a series of sensory-guided HPLC fractionations, the existence of nine groups of hitherto unknown sulfur compounds has been revealed. On the basis of spectroscopic data (MS, NMR, and IR), it was found that these compounds, trivially named allithiolanes A–I, are members of a large family of structurally closely related derivatives of 3,4-dimethylthiolane S-oxide, with the general formulas of CxHyO2S4, CxHyO3S5, and CxHyO4S6 (x = 10–18, y = 18–30). The presence of multiple stereoisomers was observed for each group of allithiolanes. Allithiolanes possess an unpleasantly bitter taste with detection thresholds in the range of 15–30 ppm. Formation pathways of these newly discovered sulfur compounds were proposed.

Competitive asymmetric transfer hydrogenation (ATH) of three differently methoxy-substituted 1-methyl-3,4-dihydroisoquinolines (1-Me-DHIQs) was carried out to examine the differences in their reactivity with six ruthenium complexes of the Noyori-Ikariya type having the general formula [Ru(II)Cl(η6-arene)(N-arylsulfonyl-DPEN)] (DPEN = 1,2-diphenylethylene-1,2-diamine). The reaction kinetics of two or three substrates at once was followed in situ by 1H NMR spectroscopy. A method originally developed for heterogeneous catalysis was used to evaluate the experimental data, providing selectivities of the catalysts to the particular substrates and affinity of these substrates to the active site. The higher reaction rate was usually connected with both higher selectivity and affinity. However, in several cases, the opposite behavior was observed, pointing to a higher selectivity towards the less reactive substrate, which can inhibit the reaction due to its higher affinity. No competitive behavior was manifested in terms of enantioselectivity. As the structure of the Noyori-Ikariya catalytic complexes is highly variable and previous structure–activity studies have often been inconclusive, the presented method may aid in the disentanglement of the complex relationships important for rational catalyst design.

The role of the sulfonamide moiety of Noyori-Ikariya [Ru(II)Cl(η 6-p-cymene)(S,S)-(N-arylsulfonyl-DPEN)] (where DPEN = 1,2-diphenylethylene-1,2-diamine) half-sandwich complexes in the asymmetric transfer hydrogenation (ATH) of imines (1-methyl-3,4-dihydroisoquinoline and 6,7-dimethoxy-1-methyl-3,4-dihydroisoquinoline) was investigated. Nine complexes were synthesized and characterized, most of which have not been previously reported and a majority of the corresponding ligands (N-arylsulfonyl-DPEN) have not been described in imine ATH. The study demonstrates that the structure of the sulfonamide fragment strongly affects the catalytic activity. By monitoring the reaction kinetics, it was found that the reactivity of certain complexes was moderately enhanced and the enantioselectivity was affected as well, albeit to a lesser extent. No simple structure–activity pattern was found, suggesting that extensive screening experiments are necessary in order to obtain the optimal catalyst for a particular substrate. The study complements other previously reported works on structure–activity relationships concerning Ru(II)-catalyzed ATH by adding a new dimension of investigation.

A method for enantioselective hydrogenation of cyclic imines with gaseous hydrogen has been developed. Easily accessible Noyori-Ikariya Ru(II) and Rh(III) complexes can be used directly without an inert atmosphere. Substrate activation has been achieved by trifluoroacetic acid. A new hydroxyl-functionalized complex is reported, showing high activity in transfer hydrogenation.

Structures and formation pathways of compounds responsible for pink discoloration of onion and leek were studied. A procedure was developed for the isolation and purification of the color compounds from various model systems and their identification by HPLC-DAD-MS/MS. In total, structures of 15 major color compounds were tentatively determined. It was found that the pigment is a complex mixture of highly conjugated species composed of two N-substituted 3,4-dimethylpyrrole-derived rings linked by either a methine or a propenylidine bridge. These two-ring units are further modified by various C1- and C3-side chains. Experiments with isotope-labeled thiosulfinates revealed that the methine bridge and C1-side chains originate from the methyl group of methiin, whereas the C3 units are derived from the propenyl group of isoalliin.

Isoquercitrin, (IQ, quercetin-3-O-β-d-glucopyranoside) is known for strong chemoprotectant activities. Acylation of flavonoid glucosides with carboxylic acids containing an aromatic ring brings entirely new properties to these compounds. Here, we describe the chemical and enzymatic synthesis of a series of IQ derivatives at the C-6″. IQ benzoate, phenylacetate, phenylpropanoate and cinnamate were prepared from respective vinyl esters using Novozym 435 (Lipase B from Candida antarctica immobilized on acrylic resin). The enzymatic procedure gave no products with “hydroxyaromatic” acids, their vinyl esters nor with their benzyl-protected forms. A chemical protection/deprotection method using Steglich reaction yielded IQ 4-hydroxybenzoate, vanillate and gallate. In case of p-coumaric, caffeic, and ferulic acid, the deprotection lead to the saturation of the double bonds at the phenylpropanoic moiety and yielded 4-hydroxy-, 3,4-dihydroxy- and 3-methoxy-4-hydroxy-phenylpropanoates. Reducing capacity of the cinnamate, gallate and 4-hydroxyphenylpropanoate towards Folin-Ciocalteau reagent was significantly lower than that of IQ, while other derivatives displayed slightly better or comparable capacity. Compared to isoquercitrin, most derivatives were less active in 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, but they showed significantly better 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid, ABTS) scavenging activity and were substantially more active in the inhibition of tert-butylhydroperoxide induced lipid peroxidation of rat liver microsomes. The most active compounds were the hydroxyphenylpropanoates.

Only four types of dimeric precursors [RuCl2(η6-arene)]2 for the synthesis of Noyori’s half sandwich diamine catalysts [RuCl(TsDPEN)(η6-arene)] are commercially available, yet so far no study has tried to systematically evaluate how these systems perform during the asymmetric transfer hydrogenation of various 3,4-dihydroisoquinolines (i.e., the typical substrates for Noyori asymmetric transfer hydrogenation benchmarking). Experiments combined with molecular modeling allowed us to assess their properties and formulate a hypothesis clarifying the difference in enantioselectivity of these systems.

A new [Ru(II)( η 6 - p -cymene)(1 R ,2 R )- N -((1 S ,2 S )-borneol-10-sulfonyl)-1,2-diphenylethylenediamine] catalyst for the asymmetric transfer hydrogenation of both 1-alkyl and 1-aryl dihydroisoquinolines has been isolated. For the first time in this type of reaction, the catalyst employs an N-alkylsulfonyl group instead of N-arylsulfonyl.

A chiral precursor of Mivacurium chloride, (R)-5′-methoxylaudanosine, was prepared using two different methods. The chiral resolution of racemic 5′-methoxylaudanosine, typically used in industry, was carried out in parallel with a procedure consisting of asymmetric transfer hydrogenation (ATH) and reductive methylation. A novel one-pot synthetic step was developed for the synthesis of racemic 5′-methoxylaudanosine. In both routes, the enantioselectivity was high but further purification was necessary to reach the level of a pharmaceutical standard. The individual synthetic steps reported herein can also be used for the synthesis of analogous bistetrahydroisoquinoline-based skeletal muscle relaxants.