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Publications

Drosihn, S.; Porzel, A.; Voigt, B.; Brandt, W.; Wagner, C.; Merzweiler, K.; Adam, G.; Conformational studies of two new brassinosteroid analogues with a 22,23-trans diol function J. Chem. Soc., Perkin Trans. 2 1999, 233-238, (1999) DOI: 10.1039/A807440B

22,24-Diepiteasterone (3) and 23,24-diepiteasterone (4) were synthesized starting from a mixture of the corresponding (22S,23S)- and (22R,23R)-epoxides. Using detailed NOE investigations and molecular dynamic simulations with explicit solvent, the preferred conformations of both compounds were determined in solution. For both compounds 3 and 4 a preferred conformation of the side chain was found. For 4, by X-ray analysis the conformation in crystalline state was determined which differs distinctly from that in solution.
Publications

Buske, A.; Busemann, S.; Mühlbacher, J.; Schmidt, J.; Porzel, A.; Bringmann, G.; Adam, G.; Antidesmone, a novel type isoquinoline alkaloid from Antidesma membranaceum (Euphorbiaceae) Tetrahedron 55, 1079-1086, (1999) DOI: 10.1016/S0040-4020(98)01107-7

A novel type of tetrahydroisoquinoline alkaloid, antidesmone (1), was isolated from Antidesma membranaceum Müll. Arg.. The structure of 1 was determined to be (5S)-1-hydroxy-4-methoxy-3-methyl-5-octyl-5,6,7,8-tetrahydroisoquinolin-8-one by spectroscopic methods (MS, 1H, 13C 2D NMR, CD) and chemical derivatisation. The absolute (S)-configuration was determined by quantumchemical calculation of CD spectra.Antidesmone (1), a novel type of tetrahydroisoquinoline alkaloid, was isolated from Antidesma membranaceum Müll. Arg. The structure of 1 was determined to be (5S)-1-hydroxy-4-methyl-5-octyl-5,6,7,8-tetrahydroisoquinolin-8-one.
Publications

Ang'edu, C. A.; Schmidt, J.; Porzel, A.; Gitu, P.; Midiwo, J. O.; Adam, G.; Coumarins from Hypericum keniense (Guttiferae) Pharmazie 54, 235-236, (1999)

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Publications

Winter, J.; Schneider, B.; Meyenburg, S.; Strack, D.; Adam, G.; Monitoring brassinosteroid biosynthetic enzymes by fluorescent tagging and HPLC analysis of their substrates and products Phytochemistry 51, 237-242, (1999) DOI: 10.1016/S0031-9422(98)00760-2

Both the vicinal side chain hydroxyl groups and the 6-oxo function of brassinosteroids were modified by fluorescence tagging. Dansylaminophenylboronic acid was used as a derivatizing agent to form fluorescent esters of brassinosteroids containing a side-chain cis-diol structure. 6-Oxo type brassinosteroids were derivatized by means of dansylhydrazine. The modified brassinosteroids, as far as possible derivatized both at the diol and the oxo group, were separated by HPLC and the optimal emission wavelength was determined. By this approach almost all brassinosteroids, including biosynthetic precursors, were susceptible to highly sensitive analysis in the fmol range. This method has been verified as an analytical tool to determine brassinosteroids in cell culture extracts and to monitor brassinosteroid biosynthetic enzymes. 24-Epibrassinolide has been detected in tomato cell suspension cultures. Several steps of brassinosteroid biosynthesis, including the Baeyer–Villiger oxidation of 24-epicastasterone to give 24-epibrassinolide, were monitored in vitro with protein preparations of the same cell culture line.
Publications

Thuy, T. T.; Ripperger, H.; Porzel, A.; Sung, T. V.; Adam, G.; Counlarins, limonoids and an alkaloid from Clausena excavata Phytochemistry 52, 511-516, (1999) DOI: 10.1016/S0031-9422(99)00122-3

In addition to a known alkaloid, some limonoids and coumarins, the new coumarins excavatins A–M have been isolated from Clausena excavata. Their structures have been assigned by NMR and CD investigations.
Publications

Thuy, T. T.; Porzel, A.; Ripperger, H.; Sung, T. V.; Adam, G.; Bishordeninyl terpene alkaloids from Zanthoxylum avicennae Phytochemistry 50, 903-907, (1999) DOI: 10.1016/S0031-9422(98)00612-8

In addition to (−)-culantraramine and (−)-culantraraminol the bishordeninyl terpene alkaloids, (−)-culantraramine N-oxide, (−)-culantraraminol N-oxide and avicennamine, have been isolated from the leaves of Zanthoxylum avicennae. Their structures have been assigned by MS and especially by NMR investigations.
Publications

Phuong, N. M.; Van Sung, T.; Porzel, A.; Schmidt, J.; Merzweiler, K.; Adam, G.; β-Carboline alkaloids from Hedyotis capitellata Phytochemistry 52, 1725-1729, (1999) DOI: 10.1016/S0031-9422(99)00280-0

Three new β-carboline alkaloids were isolated from Hedyotis capitellata (Rubiaceae). Their structures were elucidated by spectroscopic data and X-ray analysis.
Publications

Phuong, N. M.; Sung, T. V.; Porzel, A.; Schmidt, J.; Adam, G.; Two New β-Carboline Alkaloids from Hedyotis capitellata var. mollis Planta Med. 65, 761-762, (1999) DOI: 10.1055/s-2006-960861

Two new β-carboline alkaloids, hedyocapitelline and hedyocapitine, were isolated from Hedyotis capitellata var. mollis (Rubiaceae). Their structures were elucidated by spectroscopic data 1H- and 13C-NMR, MS, IR, UV).
Publications

Lichtblau, D.; Porzel, A.; Schmidt, J.; Voigt, B.; Adam, G.; Synthesis of a novel brassinosteroid type with an annelated dioxonane side chain J. Chem. Soc., Perkin Trans. 1 1999, 53-58, (1999) DOI: 10.1039/A807078D

In studies directed towards the synthesis of 25-hydroxybrassinolide 1 we found, that upon reaction of intermediate 7 with trimethylaluminium–n-butyllithium an alkylating fission of the epoxide ring and rearrangement of the tetrahydropyranyl unit takes place to afford after deprotection the new dioxonane-annelated brassinosteroid 9.
Books and chapters

Adam, G.; Schmidt, J.; Schneider, B.; Brassinosteroids Fortschritte der Chemie organischer Naturstoffe / Progress in the Chemistry of Organic Natural Products 78, 1-46, (1999) ISBN: 978-3-7091-6394-8 DOI: 10.1007/978-3-7091-6394-8_1

It was in 1979 when GROVE et al. isolated from pollen of rape (Brassica napus) a highly active plant growth promoter, named it brassinolide and elucidated its structure as (22R,23R,24S)-2α,3α, 22,23-tetrahydroxy-24-methyl-B-homo-6a-oxa-5α-cholestan-6-one (1) by spectroscopic methods including X-ray analysis (1). The original structural features of this compound and its unique high biological activity at very low concentrations stimulated intense research activities in many laboratories. Such efforts were directed towards the search for similar compounds in the plant kingdom, their chemical synthesis, biochemistry and biological mode of action leading up to their practical application in agriculture and horticulture. As a result of this interdisciplinary and rapidly processing research, brassinosteroids can nowadays be regarded as a new class of plant hormones with ubiquitous occurrence in the plant kingdom. Especially, recent molecular biological studies demonstrated their essential role for normal plant growth and development. A series of reviews have been published (2–11). Whereas the first book on brassinosteroid research covers developments up to 1990 (12), two up-to-date publications about this topic have appeared very recently (13, 14). The present article covers the literature up to December 1998 with special consideration of phytochemical, analytical and biochemical aspects.
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