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Publikationen - Natur- und Wirkstoffchemie

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Publikation

Eckermann, S.; Schröder, G.; Schmidt, J.; Strack, D.; Edrada, R. A.; Helariutta, Y.; Elomaa, P.; Kotilainen, M.; Kilpeläinen, I.; Proksch, P.; Teeri, T. H.; Schröder, J.; New pathway to polyketides in plants Nature 396, 387-390, (1998) DOI: 10.1038/24652

The repertoire of secondary metabolism (involving the production of compounds not essential for growth) in the plant kingdom is enormous, but the genetic and functional basis for this diversity is hard to analyse as many of the biosynthetic enzymes are unknown. We have now identified a key enzyme in the ornamental plant Gerbera hybrida (Asteraceae) that participates in the biosynthesis of compounds that contribute to insect and pathogen resistance. Plants transformed with an antisense construct of gchs2, a complementary DNA encoding a previously unknown function1,2, completely lack the pyrone derivatives gerberin and parasorboside. The recombinant plant protein catalyses the principal reaction in the biosynthesis of these derivatives: GCHS2 is a polyketide synthase that uses acetyl-CoA and two condensation reactions with malonyl-CoA to form the pyrone backbone of thenatural products. The enzyme also accepts benzoyl-CoA to synthesize the backbone of substances that have become of interest as inhibitors of the HIV-1 protease3,4,5. GCHS2 is related to chalcone synthase (CHS) and its properties define a new class of function in the protein superfamily. It appears that CHS-related enzymes are involved in the biosynthesis of a much larger range of plant products than was previously realized.
Publikation

Brandt, W.; A uniform molecular model of δ opioid agonist and antagonist pharmacophore conformations J. Comput. Aided Mol. Des. 12, 615-621, (1998) DOI: 10.1023/A:1008003421291

On the basis of a model of the pharmacophore conformations of agonist of the δ-opioid receptor the corresponding δ-antagonist conformations were determined by means of force field calculations. The results explain the unusual behavior of several cyclic β-casomorphin analogues on the molecular level. Thus, for instance, the model helps to understand why Tyr-c[D-Orn-2-Nal-D-Pro-Gly] is a mixed μ-agonist and δ-antagonist. Furthermore, the model is consistent with low energy conformations of other δ-antagonists such as Tyr-Tic-Phe, Tyr-Tic-Phe-Phe, naltrindole and BNTX. The occupation of a special spatial area by bulky groups close to the protonated N-terminus of opioid peptides is assumed to be highly critical for the switch from agonist to antagonist behavior.
Publikation

Wessjohann, L. A.; Sontag, B.; Entwicklung einer Enzymatischen C-C-Verknüpfung: Die Prenylierung von Aromaten GIT Labor-Fachzeitschrift 42, 229-230, (1998)

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Publikation

Wessjohann, L. A.; Sinks, U.; Benzeneselenenyl Reagents in Organic Synthesis J. Prakt. Chem. 340, 189-203, (1998) DOI: 10.1002/prac.19983400302

An account of the most commonly used reagents for the introduction of the benzeneselenyl (phenyl seleno) group is given. The review focuses on the various methods of its introduction as auxiliary, modifying or protective entity, and its subsequent removal, thereby often promoting other reactions as cyclizations or double bond formation. Less emphasis is laid on reactions of the phenylselenenylated intermediates with the PhSe‐group left intact utilizing its stabilizing properties on charged intermediates, on reagents with a modified phenyl group, e.g. chiral derivatives, or on reactions not involving intermediate CSe‐bond formation.
Publikation

Thuy, T. T.; Porzel, A.; Ripperger, H.; Sung, T. V.; Adam, G.; Chalcones and ecdysteroids from Vitex leptobotrys Phytochemistry 49, 2603-2605, (1998) DOI: 10.1016/S0031-9422(98)00411-7

In addition to some known chalcones and ecdysteroids three new chalcones have been isolated from aerial parts of Vitex leptobotrys, the structures of which have been identified as 2′,4′-dihydroxy-4,6′-dimethoxychalcone, 4′-hydroxy-4,2′,6′-trimethoxychalcone and 4,2′,4′,β-tetrahydroxy-6′-methoxy-α,β-dihydrochalcone, respectively.
Publikation

Schröder, J.; Raiber, S.; Berger, T.; Schmidt, A.; Schmidt, J.; Soares-Sello, A. M.; Bardshiri, E.; Strack, D.; Simpson, T. J.; Veit, M.; Schröder, G.; Plant Polyketide Synthases: A Chalcone Synthase-Type Enzyme Which Performs a Condensation Reaction with Methylmalonyl-CoA in the Biosynthesis of C-Methylated Chalcones Biochemistry 37, 8417-8425, (1998) DOI: 10.1021/bi980204g

Heterologous screening of a cDNA library from Pinus strobus seedlings identified clones for two chalcone synthase (CHS) related proteins (PStrCHS1 and PStrCHS2, 87.6% identity). Heterologous expression in Escherichia coli showed that PStrCHS1 performed the typical CHS reaction, that it used starter CoA-esters from the phenylpropanoid pathway, and that it performed three condensation reactions with malonyl-CoA, followed by the ring closure to the chalcone. PstrCHS2 was completely inactive with these starters and also with linear CoA-esters. Activity was detected only with a diketide derivative (N-acetylcysteamine thioester of 3-oxo-5-phenylpent-4-enoic acid) that corresponded to the CHS reaction intermediate postulated after the first condensation reaction. PstrCHS2 performed only one condensation, with 6-styryl-4-hydroxy-2-pyrone derivatives as release products. The enzyme preferred methylmalonyl-CoA against malonyl-CoA, if only methylmalonyl-CoA was available. These properties and a comparison with the CHS from Pinussylvestris suggested for PstrCHS2 a special function in the biosynthesis of secondary products. In contrast to P. sylvestris, P. strobus contains C-methylated chalcone derivatives, and the methyl group is at the position predicted from a chain extension with methylmalonyl-CoA in the second condensation of the biosynthetic reaction sequence. We propose that PstrCHS2 specifically contributes the condensing reaction with methylmalonyl-CoA to yield a methylated triketide intermediate. We discuss a model that the biosynthesis of C-methylated chalcones represents the simplest example of a modular polyketide synthase.
Publikation

Schmidt, J.; Porzel, A.; Adam, G.; Brassinosteroids and a pregnane glucoside from Daucus carota Phytochem. Anal. 9, 14-20, (1998) DOI: 10.1002/(SICI)1099-1565(199801/02)9:1<14::AID-PCA381>3.0.CO;2-4

The brassinosteroids brassinolide, castasterone and 24‐epi‐castasterone could be isolated and identified from seeds of Daucus carota . Furthermore, a new pregnanolone glucoside was identified as β‐D ‐glucopyranosyl‐(1‐2)‐β‐D ‐glucopyranosyl‐3β‐hydroxy‐5α‐pregnane‐20‐one (sophorosylpregnanolone) by nuclear magnetic resonance spectroscopy, liquid chromatography‐mass spectrometry and gas chromatography‐mass spectrometry.
Publikation

Schmidt, J.; Porzel, A.; Adam, G.; 3α,20-dihydroxy-3β,25-epoxylupane, a triterpene from Rhus typhina Phytochemistry 49, 2049-2051, (1998) DOI: 10.1016/S0031-9422(98)00398-7

A new triterpene, 3α,20-dihydroxy-3β,25-epoxylupane, was isolated and structurally elucidated from flowers of the sumach tree Rhus typhina (Anacardiaceae).
Publikation

Quan, T. D.; Porzel, A.; Ripperger, H.; Sung, T. V.; Adam, G.; Photochemistry of Artemisinin Derivatives Nat. Prod. Lett. 12, 151-159, (1998) DOI: 10.1080/10575639808048285

Photochemical reactivity of some oxoalkyl derivatives of dihydroartemisinin as well as the reaction of dihydroartemisinin with lead tetraacetate/iodine under visible light have been studied.
Publikation

Phuong, N. M.; Sung, T. V.; Schmidt, J.; Porzel, A.; Adam, G.; Capitelline - A New Indole Alkaloid from Hedyotis capitellata Nat. Prod. Lett. 11, 93-100, (1998) DOI: 10.1080/10575639808041203

A new indole monoterpene alkaloid, named capitelline (1), was isolated from Hedyotis capitellata (Rubiaceae). Its structure was elucidated by spectroscopic data (1H- and 13C-NMR, MS, IR, UV).
  • Die Leibniz-Gemeinschaft
  • Digitalisierung in der Landwirtschaft
  • Martin-Luther Universität Halle
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