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Publikationen - Natur- und Wirkstoffchemie

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Publikation

Ödman, P.; Wessjohann, L. A.; Bornscheuer, U. T.; Chemoenzymatic Dynamic Kinetic Resolution of Acyloins J. Org. Chem. 70, 9551-9555, (2005) DOI: 10.1021/jo051661n

Acyloins (α-hydroxy ketones) are important building blocks in organic synthesis, e.g., for the total synthesis of epothilones. Optically pure acyloins can be obtained by lipase-catalyzed kinetic resolution (KR) of the racemate with, for example, Burkholderia cepacia lipase, but this process suffers from a yield limitation of 50%. To devise a dynamic kinetic resolution (DKR), we studied the racemization of two different acyloins and corresponding esters with various amine bases and ion exchangers. No combination of base and solvent was found that could selectively racemize the acyloin or corresponding ester under the conditions needed for a DKR. In contrast to bases, acidic resins (ARs) were found to racemize the acyloins selectively in n-hexane and in water. Unfortunately, the AR deactivated the lipase, preventing a one-pot DKR. Minor side reactions involving the AR, the substrate acyloin, and the vinyl ester acyl donor were also observed. However, an efficient DKR was made possible by the spatial separation of lipase and ion exchanger, with enzymatic transesterification and AR-catalyzed racemization taking place simultaneously in two compartments connected by a pump loop. The conversion of substrate alcohol was 91%, the selectivity toward the product butyrate ester 90%, and the enantiomeric excess of the (S)-product 93% ee.
Publikation

Nguyen, T. H. V.; Nguyen, T. H. A.; Tran, V. S.; Franke, K.; Wessjohann, L.; Three phthalide derivatives from Angelica sinensis Rhizomes Vietnam J. Chem. 43, 119-122, (2005)

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Publikation

Nguyen, T. H. V.; Nguyen, T. H. A.; Tran, V. S.; Franke, K.; Wessjohann, L.; Studies on chemical composition of Angelica sinensis. Part VI - Angelicolide and three other compounds Vietnam J. Chem. 43, 749-752, (2005)

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Publikation

Nguyen, T. H. V.; Nguyen, T. H. A.; Tran, V. S.; Franke, K.; Wessjohann, L.; Studies on chemical composition of Angelica sinensis's. V - The nitrogen-containing compounds Vietnam J. Chem. 43, 605-609, (2005)

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Publikation

Nguyen, T. H. V.; Nguyen, T. H. A.; Tran, V. S.; Franke, K.; Wessjohann, L.; Four phthalides from the roots of Angelica sinensis Vietnam J. Chem. 43, 228-231, (2005)

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Publikation

Nguyen, T. H. V.; Nguyen, T. H. A.; Tran, V. S.; Franke, K.; Wessjohann, L.; Chemical study of Angelica sinensis's roots Vietnam J. Chem. 43, 494-498, (2005)

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Publikation

Nguyen, M. C.; Tran, Q. H.; Nguyen, Q. C.; Arnold, N.; Wessjohann, L.; Antifungal compounds from the vietnamese plant Bousingonia Mekongense Adv. Nat. Sci. (Vietnam) 6, 227-230, (2005)

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Publikation

Lipka, V.; Dittgen, J.; Bednarek, P.; Bhat, R.; Wiermer, M.; Stein, M.; Landtag, J.; Brandt, W.; Rosahl, S.; Scheel, D.; Llorente, F.; Molina, A.; Parker, J.; Somerville, S.; Schulze-Lefert, P.; Pre- and Postinvasion Defenses Both Contribute to Nonhost Resistance in Arabidopsis Science 310, 1180-1183, (2005) DOI: 10.1126/science.1119409

Nonhost resistance describes the immunity of an entire plant species against nonadapted pathogen species. We report that Arabidopsis PEN2 restricts pathogen entry of two ascomycete powdery mildew fungi that in nature colonize grass and pea species. The PEN2 glycosyl hydrolase localizes to peroxisomes and acts as a component of an inducible preinvasion resistance mechanism. Postinvasion fungal growth is blocked by a separate resistance layer requiring the EDS1-PAD4-SAG101 signaling complex, which is known to function in basal and resistance (R) gene–triggered immunity. Concurrent impairment of pre- and postinvasion resistance renders Arabidopsis a host for both nonadapted fungi.
Publikation

Kramell, R.; Schmidt, J.; Herrmann, G.; Schliemann, W.; N-(Jasmonoyl)tyrosine-Derived Compounds from Flowers of Broad Beans (Vicia faba) J. Nat. Prod. 68, 1345-1349, (2005) DOI: 10.1021/np0501482

Two new amide-linked conjugates of jasmonic acid, N-[(3R,7R)-(−)-jasmonoyl]-(S)-dopa (3) and N-[(3R,7R)-(−)-jasmonoyl]-dopamine (5), were isolated in addition to the known compound N-[(3R,7R)-(−)-jasmonoyl]-(S)-tyrosine (2) from the methanolic extract of flowers of broad bean (Vicia faba). Their structures were proposed on the basis of spectroscopic data (LC-MS/MS) and chromatographic properties on reversed and chiral phases and confirmed by partial syntheses. Furthermore, tyrosine conjugates of two cucurbic acid isomers (7, 8) were detected and characterized by LC-MS. Crude enzyme preparations from flowers of V. faba hydroxylated both (±)-2 and N-[(3R,7R/3S,7S)-(−)-jasmonoyl]tyramine [(±)-4] to (±)-3 and (±)-5, respectively, suggesting a possible biosynthetic relationship. In addition, a commercial tyrosinase (mushroom) and a tyrosinase-containing extract from hairy roots of red beet exhibited the same catalytic properties, but with different substrate specificities. The conjugates (±)-2, (±)-3, (±)-4, and (±)-5 exhibited in a bioassay low activity to elicit alkaloid formation in comparison to free (±)-jasmonic acid [(±)-1].
Publikation

Hornung, E.; Krueger, C.; Pernstich, C.; Gipmans, M.; Porzel, A.; Feussner, I.; Production of (10E,12Z)-conjugated linoleic acid in yeast and tobacco seeds BBA-Mol. Cell Biol. Lipids 1738, 105-114, (2005) DOI: 10.1016/j.bbalip.2005.11.004

The polyenoic fatty acid isomerase from Propioniumbacterium acnes (PAI) was expressed in E. coli and biochemically characterized. PAI catalyzes the isomerization of a methylene-interrupted double bond system to a conjugated double bond system, creating (10E,12Z)-conjugated linoleic acid (CLA). PAI accepted a wide range of free polyunsaturated fatty acids as substrates ranging from 18:2 fatty acids to 22:6, converting them to fatty acids with two or three conjugated double bonds. For expression of PAI in yeast the PAI-sequence encoding 20 N-terminal amino acid residues was altered for optimal codon usage, yielding codon optimized PAI (coPAI). The percentage of 10,12-CLA of total esterified fatty acids was 8 times higher in yeast transformed with coPAI than in cells transformed with PAI. CLA was detected in amounts up to 5.7% of total free fatty acids in yeast transformed with coPAI but none was detected in yeast transformed with PAI. PAI or coPAI under the control of the constitutive CaMV 35S promoter or the seed-specific USP promoter was transformed into tobacco plants. CLA was only detected in seeds in coPAI-transgenic plants. The amount of CLA detected in esterified fatty acids was up to 0.3%, in free fatty acids up to 15%.
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  • Martin-Luther Universität Halle
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