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Displaying results 1 to 10 of 181.

Publications

Pereira, C.; Barreto Júnior, C. B.; Kuster, R. M.; Simas, N. K.; Sakuragui, C. M.; Porzel, A.; Wessjohann, L.; Flavonoids and a neolignan glucoside from Guarea macrophylla (Meliaceae) Quím. Nova 35, 1123-1126, (2012) DOI: 10.1590/S0100-40422012000600010

This work describes the phytochemical study of the methanol extract obtained from leaves of Guarea macrophylla, leading to the isolation and identification of three flavonoid glycosides (quercetin 3-O-β-D-glucopyranoside, quercetin 3-O-b-D-galactopyranoside, kaempferol 7-O-β-D-glucopyranoside) and a neolignan glucoside, dehydrodiconiferyl alcohol-4-β-D-glucoside. All compounds were identified by a combination of spectroscopic methods (1H, 1D, 2D NMR, 13C and UV), ESI-MS and comparison with the literature data. This is the first report of flavonoids in the genus Guarea and of a neolignan glucoside in the Meliaceae family.
Publications

Parthier, C.; Görlich, S.; Jaenecke, F.; Breithaupt, C.; Bräuer, U.; Fandrich, U.; Clausnitzer, D.; Wehmeier, U. F.; Böttcher, C.; Scheel, D.; Stubbs, M. T.; The O-Carbamoyltransferase TobZ Catalyzes an Ancient Enzymatic Reaction Angew. Chem. Int. Ed. 51, 4046-4052, (2012) DOI: 10.1002/anie.201108896

An ancient reaction vessel: TobZ carbamoylates the antibiotic tobramycin to form nebramycin 5′. The YrdC‐like domain (blue) catalyzes the formation of the novel intermediate carbamoyladenylate, which is channeled through a common “reaction chamber” to the Kae1‐like domain (brown), site of carbamoyl transfer.
Publications

Parthier, C.; Görlich, S.; Jaenecke, F.; Breithaupt, C.; Bräuer, U.; Fandrich, U.; Clausnitzer, D.; Wehmeier, U. F.; Böttcher, C.; Scheel, D.; Stubbs, M. T.; Die O-Carbamoyltransferase TobZ katalysiert eine enzymatische Reaktion frühen Ursprungs Angew. Chem. 124, 4122-4128, (2012) DOI: 10.1002/ange.201108896

Ein uraltes Reaktionsgefäß: TobZ carbamoyliert das Antibiotikum Tobramycin unter Bildung von Nebramycin‐5′. Dabei katalysiert die YrdC‐ähnliche Domäne (blau) die Bildung eines intermediären Carbamoyladenylats, das innerhalb einer tunnelartigen Reaktionskammer zur Kae1‐ähnlichen Domäne (braun), dem Ort des Carbamoyltransfers, transferiert wird.
Publications

Palm-Forster, M. A. T.; Eschen-Lippold, L.; Lee, J.; A mutagenesis-based screen to rapidly identify phosphorylation sites in mitogen-activated protein kinase substrates Anal. Biochem. 427, 127-129, (2012) DOI: 10.1016/j.ab.2012.05.015

Identification and characterization of protein phosphorylation sites often requires mass spectrometric analysis, which is not trivial or accessible to many laboratories. Here, a targeted strategy to mutagenize putative phosphorylation sites within mitogen-activated protein kinase (MAPK) substrates is described. This employs a combination of standard type II with type IIs restriction enzymes to rapidly create individual or multiple phosphorylation site mutant versions of kinase substrates with high efficiency, thereby reducing the cost for screening mutated clones.
Publications

Nowack, M.; Harashima, H.; Dissmeyer, N.; Zhao, X.; Bouyer, D.; Weimer, A.; De Winter, F.; Yang, F.; Schnittger, A.; Genetic Framework of Cyclin-Dependent Kinase Function in Arabidopsis Dev. Cell 22, 1030-1040, (2012) DOI: 10.1016/j.devcel.2012.02.015

Cyclin-dependent kinases (CDKs) are at the heart of eukaryotic cell-cycle control. The yeast Cdc2/CDC28 PSTAIRE kinase and its orthologs such as the mammalian Cdk1 have been found to be indispensable for cell-cycle progression in all eukaryotes investigated so far. CDKA;1 is the only PSTAIRE kinase in the flowering plant Arabidopsis and can rescue Cdc2/CDC28 mutants. Here, we show that cdka;1 null mutants are viable but display specific cell-cycle and developmental defects, e.g., in S phase entry and stem cell maintenance. We unravel that the crucial function of CDKA;1 is the control of the plant Retinoblastoma homolog RBR1 and that codepletion of RBR1 and CDKA;1 rescued most defects of cdka;1 mutants. Our work further revealed a basic cell-cycle control system relying on two plant-specific B1-type CDKs, and the triple cdk mutants displayed an early germline arrest. Taken together, our data indicate divergent functional differentiation of Cdc2-type kinases during eukaryote evolution.
Publications

Neves Filho, R. A. W.; Stark, S.; Westermann, B.; Wessjohann, L. A.; The multicomponent approach to N-methyl peptides: total synthesis of antibacterial (–)-viridic acid and analogues Beilstein J. Org. Chem. 8, 2085-2090, (2012) DOI: 10.3762/bjoc.8.234

Two syntheses of natural viridic acid, an unusual triply N-methylated peptide with two anthranilate units, are presented. The first one is based on peptide-coupling strategies and affords the optically active natural product in 20% overall yield over six steps. A more economical approach with only four steps leads to the similarly active racemate by utilizing a Ugi four-component reaction (Ugi-4CR) as the key transformation. A small library of viridic acid analogues is readily available to provide first SAR insight. The biological activities of the natural product and its derivatives against the Gram-negative bacterium Aliivibrio fischeri were evaluated.
Publications

Neves Filho, R. A. W.; Brauer, M. C. N.; Palm-Forster, M. A. T.; de Oliveira, R. N.; Wessjohann, L. A.; Patented Catalysts for the Synthesis and Biological Applications of Dihydropyrimidinones: Recent Advances of the Biginelli Reaction Recent Pat. Catal. 1, 51-73, (2012) DOI: 10.2174/2211548X11201010051

The acid-catalyzed and thermal multicomponent cyclocondensation between an aldehyde, a beta-keto ester and urea to generate dihydropyrimidinones (DHPMs) is one of the best studied multicomponent reactions in organic synthesis. It is frequently employed in the synthesis of natural products and biologically active compounds. After several years under academic development, this reaction drew the attention of researchers in the chemical and pharmaceutical industry. This critical review is focused on the development and applications of the Biginelli three component reaction (B-3CR) patented in the last three decades.
Publications

Neves Filho, R. A. W.; Stark, S.; Morejon, M. C.; Westermann, B.; Wessjohann, L. A.; 4-Isocyanopermethylbutane-1,1,3-triol (IPB): a convertible isonitrile for multicomponent reactions Tetrahedron Lett. 53, 5360-5363, (2012) DOI: 10.1016/j.tetlet.2012.07.064

The synthesis and applications of 4-isocyanopermethylbutane-1,1,3-triol (IPB) as a new convertible isonitrile (isocyanide) for isocyanide-based multicomponent reactions (IMCRs) like Ugi, Ugi-Smiles, and Passerini reactions are described. The primary products obtained from these IMCRs can be converted into highly activated N-acylpyrroles, which upon treatment with nucleophiles can be transformed into carboxylic acids, esters, amides, alcohols, and olefins. In this sense the reagent can be seen as a neutral carbanion equivalent to formate (HO2C−), and carboxylates or carboxamides etc. (RNu-CO−).
Publications

Müller, A. O.; Mrestani-Klaus, C.; Schmidt, J.; Ulbrich-Hofmann, R.; Dippe, M.; New cardiolipin analogs synthesized by phospholipase D-catalyzed transphosphatidylation Chem. Phys. Lipids 165, 787-793, (2012) DOI: 10.1016/j.chemphyslip.2012.09.005

Cardiolipin (CL) and related diphosphatidyl lipids are hardly accessible because of the complexity of their chemical synthesis. In the present paper, the transphosphatidylation reaction catalyzed by phospholipase D (PLD) from Streptomyces sp. has been proven as an alternative enzyme-assisted strategy for the synthesis of new CL analogs. The formation of this type of compounds from phosphatidylcholine was compared for a series of N- and C2-substituted ethanolamine derivatives as well as non-charged alcohols such as glycerol and ethylene glycol. The rapid exchange of the choline head group by ethanolamine derivatives having a low molecular volume (diethanolamine and serinol) gave rise to an efficient production of the corresponding CL analogs. In contrast, the yields were comparably low in the reaction with bulky nitrogenous acceptor alcohols (triethanolamine, tris(hydroxymethyl)aminomethane, tetrakis(hydroxyethyl)ammonium) or the non-charged alcohols. Therefore, a strong dependence of the conversion of the monophosphatidyl to the diphosphatidyl compound on steric parameters and the head group charge was concluded. The enzyme-assisted strategy was used for the preparation of purified diphosphatidyldiethanolamine and diphosphatidylserinol.
Publications

Ley, J. P.; Dessoy, M.; Paetz, S.; Blings, M.; Hoffmann-Lücke, P.; Reichelt, K. V.; Krammer, G. E.; Pienkny, S.; Brandt, W.; Wessjohann, L.; Identification of Enterodiol as a Masker for Caffeine Bitterness by Using a Pharmacophore Model Based on Structural Analogues of Homoeriodictyol J. Agr. Food Chem. 60, 6303-6311, (2012) DOI: 10.1021/jf301335z

Starting from previous structure–activity relationship studies of taste modifiers based on homoeriodictyol, dihydrochalcones, deoxybenzoins, and trans-3-hydroxyflavones as obvious analogues were investigated for their masking effect against caffeine. The most active compounds of the newly investigated taste modifiers were phloretin, the related dihydrochalcones 3-methoxy-2′,4,4′-trihydroxydihydrochalcone and 2′,4-dihydroxy-3-methoxydihydrochalcone, and the deoxybenzoin 2-(4-hydroxy-3-methoxyphenyl)-1-(4-hydroxyphenyl)ethanone. Starting with the whole set of compounds showing activity >22%, a (Q)SAR pharmacophore model for maskers of caffeine bitterness was calculated to explain the structural requirements. After docking of the pharmacophore into a structural model of the broadly tuned bitter receptor hTAS2R10 and docking of enterolactone and enterodiol as only very weakly related structures, it was possible to predict qualitatively their modulating activity. Enterodiol (25 mg L–1) reduced the bitterness of the 500 mg L–1 caffeine solution by about 30%, whereas enterolactone showed no masking but a slight bitter-enhancing effect.
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