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Publikationen - Natur- und Wirkstoffchemie

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Publikation

Fredericks, W. J.; McGarvey, T.; Wang, H.; Lal, P.; Puthiyaveettil, R.; Tomaszewski, J.; Sepulveda, J.; Labelle, E.; Weiss, J. S.; Nickerson, M. L.; Kruth, H. S.; Brandt, W.; Wessjohann, L. A.; Malkowicz, S. B.; The Bladder Tumor Suppressor Protein TERE1 (UBIAD1) Modulates Cell Cholesterol: Implications for Tumor Progression DNA Cell Biol. 30, 851-864, (2011) DOI: 10.1089/dna.2011.1315

Convergent evidence implicates the TERE1 protein in human bladder tumor progression and lipid metabolism. Previously, reduced TERE1 expression was found in invasive urologic cancers and inhibited cell growth upon re-expression. A role in lipid metabolism was suggested by TERE1 binding to APOE, a cholesterol carrier, and to TBL2, a candidate protein in triglyceride disorders. Natural TERE1 mutations associate with Schnyder's corneal dystrophy, characterized by lipid accumulation. TERE1 catalyzes menaquinone synthesis, known to affect cholesterol homeostasis. To explore this relationship, we altered TERE1 and TBL2 dosage via ectopic expression and interfering RNA and measured cholesterol by Amplex red. Protein interactions of wild-type and mutant TERE1 with GST-APOE were evaluated by binding assays and molecular modeling. We conducted a bladder tumor microarray TERE1 expression analysis and assayed tumorigenicity of J82 cells ectopically expressing TERE1. TERE1 expression was reduced in a third of invasive specimens. Ectopic TERE1 expression in J82 bladder cancer cells dramatically inhibited nude mouse tumorigenesis. TERE1 and TBL2 proteins inversely modulated cellular cholesterol in HEK293 and bladder cancer cells from 20% to 50%. TERE1 point mutations affected APOE interactions, and resulted in cholesterol levels that differed from wild type. Elevated tumor cell cholesterol is known to affect apoptosis and growth signaling; thus, loss of TERE1 in invasive bladder cancer may represent a defect in menaquinone-mediated cholesterol homeostasis that contributes to progression.
Publikation

Dubberke, S.; Abbas, M.; Westermann, B.; Oxidative allylic rearrangement of cycloalkenols: Formal total synthesis of enantiomerically pure trisporic acid B Beilstein J. Org. Chem. 7, 421-425, (2011) DOI: 10.3762/bjoc.7.54

Enantiomerically highly enriched unsaturated β-ketoesters bearing a quaternary stereocenter can be utilized as building blocks for the synthesis of natural occurring terpenes, i. a., trisporic acid and its derivatives. An advanced building block has been synthesized in a short reaction sequence, which involves an oxidative allylic rearrangement initiated by pyridinium dichromate (PDC) as the key step.
Publikation

Dąbrowska, P.; Shabab, M.; Brandt, W.; Vogel, H.; Boland, W.; Isomerization of the Phytohormone Precursor 12-Oxophytodienoic Acid (OPDA) in the Insect Gut J. Biol. Chem. 286, 22348-22354, (2011) DOI: 10.1074/jbc.M111.244509

12-Oxophytodienoic acid (OPDA) is isomerized in the gut of herbivorous insects to tetrahydrodicranenone B (iso-OPDA). The transformation is achieved by a glutathione S-transferase present in the gut epithelium. Experiments with 9-[2H]-iso-OPDA demonstrated the complete retention of the deuterium atom in the product 11-[2H]-OPDA consistent with an intramolecular 1,3-hydrogen shift. Homology modeling based on the x-ray structure of a glutathione S-transferase from Anopheles gambiae revealed that the co-factor glutathione does not covalently bind to the substrate but appears to be involved in the initial deprotonation and enolization of the OPDA. The transformation resembles that of a mammalian GST-catalyzed isomerization of Δ5-3-ketosteroids to Δ4-3-ketosteroids or the conversion of prostaglandin A1 to the biologically inactive prostaglandin B1.
Publikation

Brandt, W.; Herberg, T.; Wessjohann, L.; Systematic conformational investigations of peptoids and peptoid-peptide chimeras Biopolymers 96, 651-668, (2011) DOI: 10.1002/bip.21620

Peptoids are originally defined as N‐substituted oligoglycine derivatives, and in a broader definition as N‐substituted peptides (peptoid–peptide chimeras). Both types were systematically investigated by force field calculations. The Merck MMFF and YASARA2 force fields were shown to be, among others, the most suitable ones for conformational investigations of peptoids with no missing parameterizations, in contrast to AMBER or CHARMM. Ramachandran‐like plots were calculated for dipeptoids and chimeras using energy calculations and grid searches by varying the dihedral angels Φ and Ψ in steps of 10° for s‐cis‐ and s‐trans amide bonds. Barriers as well as low energy conformations are compared to peptide Ramachandran plots, showing that peptoids have both, more barriers due to additional steric interactions as well as access to minimum conformations not accessible by peptides. Low energy conformations of dimers were used as starting conformations of higher oligomers of the peptoids for extensive molecular dynamics simulations over 10 or 20 ns with the YASARA2 force field and an explicit water solvent box to evaluate their potential to form secondary structural elements. Especially peptoids with aminoisobutyric acid‐like monomer units were found to form left‐handed or polyproline‐like helices also known from less common natural peptides. Furthermore, new secondary structures appear feasible based on stable conformations outside the allowed areas of the Ramachandran plot for peptides, but allowed for peptoids.
Publikation

Block, M.; Bette, M.; Wagner, C.; Schmidt, J.; Steinborn, D.; Rhodium(I) complexes with κP coordinated ω-phosphinofunctionalized alkyl phenyl sulfide, sulfoxide and sulfone ligands and their reactions with sodium bis(trimethylsilyl)amide and Ag[BF4] J. Organomet. Chem. 696, 1768-1781, (2011) DOI: 10.1016/j.jorganchem.2010.12.019

Reactions of ω-diphenylphosphinofunctionalized alkyl phenyl sulfides Ph2P(CH2)nSPh (n = 1, 1a; 2, 2a; 3, 3a), sulfoxides Ph2P(CH2)nS(O)Ph (n = 1, 1b; 2, 2b; 3, 3b) and sulfones Ph2P(CH2)nS(O)2Ph (n = 1, 1c; 2, 2c; 3, 3c) with dinuclear chlorido bridged rhodium(I) complexes [(RhL2)2(μ-Cl)2] (L2 = cycloocta-1.5-diene, cod, 4; bis(diphenylphosphino)ethane, dppe, 5) afforded mononuclear Rh(I) complexes of the type [RhCl{Ph2P(CH2)nS(O)xPh-κP}(cod)]1 (n/x = 1/0, 6a; 1/1, 6b; 1/2, 6c; 2/0, 8a; 2/1, 8b; 2/2, 8c; 3/0, 10a; 3/1, 10b; 3/2, 10c) and [RhCl{Ph2P(CH2)nS(O)xPh-κP}(dppe)] (n/x = 1/0, 7a; 1/1, 7b; 1/2, 7c; 2/0, 9a; 2/1, 9b; 2/2, 9c; 3/0, 11a; 3/1, 11b; 3/2, 11c) having the P^S(O)x ligands κP coordinated. Addition of Ag[BF4] to complexes 6–11 in CH2Cl2 led with precipitation of AgCl to cationic rhodium complexes of the type [Rh{Ph2P(CH2)nS(O)xPh-κP,κS/O}L2][BF4] having bound the P^S(O)x ligands bidentately in a κP,κS (13a–18a, 15b–18b) or a κP,κO (13b, 14b, 13c–18c) coordination mode. Unexpectedly, the addition of Ag[BF4] to 6a in THF afforded the trinuclear cationic rhodium(I) complex [Rh3(μ-Cl)(μ-Ph2PCH2SPh-κP:κS)4][BF4]2·4THF (12·4THF) with a four-membered Rh3Cl ring as basic framework. Addition of sodium bis(trimethylsilyl)amide to complexes 6–11 led to a selective deprotonation of the carbon atom neighbored to the S(O)x group (α-C) yielding three different types of organorhodium complexes: a) Organorhodium intramolecular coordination compounds of the type [Rh{CH{S(O)xPh}CH2CH2PPh2-κC,κP}L2] (22a–c, 23a–c), b) zwitterionic complexes [Rh{Ph2PCHS(O)xPh-κP,κS/O}L2] having κP,κS (21a, 21b) and κP,κO (20b/c, 21c) coordinated anionic [Ph2PCHS(O)xPh] ligands, and c) the dinuclear rhodium(I) complex [{Rh{μ-CH(SPh)PPh2-κC:κP}(cod)}2] (19). All complexes were fully characterized spectroscopically and complexes 15b, 15c, 12·4THF and 19·THF additionally by X-ray diffraction analysis. DFT calculations of zwitterionic complexes gave insight into the coordination mode of the [Ph2PCHS(O)Ph] ligand (κP,κS versus κP,κO).
Publikation

Barreto, A. d. F. S.; Vercillo, O. E.; Birkett, M. A.; Caulfield, J. C.; Wessjohann, L. A.; Andrade, C. K. Z.; Fast and efficient microwave-assisted synthesis of functionalized peptoids via Ugi reactions Org. Biomol. Chem. 9, 5024-5027, (2011) DOI: 10.1039/C1OB05471F

A wide range of N-alkylglycines (peptoids) can be efficiently prepared viaUgi reactions using microwave irradiations. The results confirm the versatility and efficiency of the methodology for the preparation of functionalized peptoids. The products can be used in consecutive Ugi reactions to yield cyclic peptoids of potential biological interest.
Publikation

Bakthir, H.; Awadh Ali, N. A.; Arnold, N.; Teichert, A.; Wessjohann, L.; Anticholinesterase activity of endemic plant extracts from Soqotra Afr. J. Tradit. Complement. Altern. Med. 8, 296-299, (2011) DOI: 10.4314/ajtcam.v8i3.65292

A total of 30 chloroform and methanol extracts from the following endemic Soqotran plants Acridocarpus socotranus Olive, Boswellia socotranao Balf.fil, Boswellia elongata Balf. fil., Caralluma socotrana N. Br, Cephalocroton socotranus Balf.f, Croton socotranus Balf. fil.., Dendrosicycos socotrana Balf.f., Dorstenia gigas Schweinf. ex Balf. fil., Eureiandra balfourii Cogn. & Balf. fil., Kalanchoe farinaceae Balf.f, Limonium sokotranum (Vierh) Radcl. Sm), Oldenlandia pulvinata, Pulicaria diversifolia( Balf. and Pulicaria stephanocarpa Balf. were screened for their acetylcholinesterase inhibitory activity by using in vitro Ellman method at 50 and 200 μg/ml concentrations. Chloroform extracts of Croton socotranus, Boswellia socotrana, Dorstenia gigas, and Pulicaria stephanocarpa as well as methanol extracts of Eureiandra balfourii exhibited inhibitory activities higher than 50 % at concentration of 200 μg. At a concentrations of 50 μg, the chloroform extract of Croton socotranus exhibited an inhibition of 40.6 %.
Bücher und Buchkapitel

Wessjohann, L. A.; Ostrowski, S.; Bakulev, V.; Berseneva, V.; Bogdanov, A. V.; Romanova, I. P.; Mironov, V. F.; Larionova, O. A.; Shaikhutdinova, G. R.; Sinyashin, O. G.; Baibulatova, N. Z.; Dokichev, V. A.; Fedorova, O. V.; Ovchinnikova, I. G.; Rusinov, G. L.; Titova, J. A.; Nasonova, A.; Kim, D.-J.; Kim, K.-S.; Jang, Y. M.; Kim, S. J.; Rakhimova, E. B.; Minnebaev, A. B.; Akhmetova, V. R.; Qin, C.; Zhang, R.; Wang, Q.; Ren, J.; Tian, L.; Mironov, M. A.; Demina, T. S.; Tcoy, A. M.; Akopova, T. A.; Markvicheva, E. A.; Chernyshenko, A. O.; Zelenetski, A. N.; Pandit, S. S.; Multi-Component Reactions in Supramolecular Chemistry and Material Science (Mironov, M. A., ed.). Adv. Exp. Med. Biol. 699, 173-201, (2011) ISBN: 978-1-4419-7270-5 DOI: 10.1007/978-1-4419-7270-5_6

Multi-component reactions of building blocks with more than one MCR-reactive group will give rise to oligomeric MCR products. The proper choice of at least two bifunctional building blocks will give either a polymeric or a cyclic product. Apart from polymerization, repetitive or consecutive Ugi reactions have been used to produce linear MCR-heterooligomers with such building blocks.
Bücher und Buchkapitel

Wessjohann, L. A.; Nin Brauer, M. C.; Brand, K.; Chalcogen-Based Organocatalysis (Mahrwald, R., ed.). 209-314, (2011) ISBN: 978-90-481-3865-4 DOI: 10.1007/978-90-481-3865-4_7

Most current organocatalysts are based on nitrogen (or phosphorus) as reactive atom, including also most processes depending on proton acidity and/or Lewis basicity. Only few organocatalytic systems use organochalcogens, although such reactions are of great importance in nature, especially evident in hydrolases with serine or cysteine as catalytic hotspot, or in oxidoreductases with cysteine or selenocysteine as key players. Catalytic processes in nature commonly rely on the nucleophilic or redox properties of chalcogen atoms. Accordingly early attempts in chemical catalysis using organochalcogens concentrate either on systems reminiscent of catalytic diads and triads of enzymes with catalysts consisting of a hydroxyl or sulfhydryl group that is activated as nucleophile by a neighboring base (catalytic diads and triads). Other “traditional” uses of chalcogen-based catalysts comprise chiral dioxiranes and oxaziranes for epoxidations, and sulfur redox catalysts, the latter especially in the application of sulfur ylides covered by the predominant work of Aggarwal et al. Since the advent of “Organocatalysis” as a distinct subfield of catalysis, not only these traditional organochalcogen catalyst systems excelled; also new applications are more systematically studied now, including not only oxygen and sulfur but increasingly selenium – and to a smaller extent – even tellurium based catalysis [372]. If nature and its several thousand years of selection of catalysis modes serve as a reference, group VI-based catalysis is yet very much below its real potential in chemical organocatalysis. This contribution thus aims at giving the reader an entry into this so much underutilized field, which offers ample room especially for those who like to try new paths and who not only wish expand on existing processes of well ­established nitrogen-based catalysts.
Publikation

Jindaprasert, A.; Samappito, S.; Springob, K.; Schmidt, J.; Gulder, T.; De-Eknamkul, W.; Bringmann, G.; Kutchan, T. M.; In Vitro Plants, Callus and Root Cultures of Plumbago indica and Their Biosynthetic Potential for Plumbagin King Mongkut\'s Agro-Industry Journal 2, 53-65, (2010)

In vitro cultured plants of Plumbago indica L. were established from nodal segments and micropropagated on hormone-free LS medium. These in vitro plantlets produced plumbagin with the content 0.79-0.87 mg g-1 dry weight which was more than half of the content found in the whole roots of greenhouse plants. Root and callus cultures were also initiated from stem and young leaf explants, respectively. The root cultures maintained in hormone-free MS medium accumulated 0.28 mg g-1 plumbagin whereas the callus cultures grown on MS medium supplemented with 1.0 mg l-1 2,4-dichloropenoxyacetic acid (2,4-D) and 0.1 mg l-1 kinetin contained only 0.013 mg g-1 of the compound. In addition to plumbagin, its related compounds plumbagic acid and plumbagic acid glucoside were also found specifically in the root tissues of the micropropagated plantlets and the root cultures. These results suggested the biosynthetic potential for the plumbagin-derived compounds in the tissues of in vitro plants and organ cultures which allows us to use them as materials for studying genes and enzymes involved in the naphthoquinone formation in P. indica.
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