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Displaying results 1 to 10 of 22.

Publications

Voigt, B.; Porzel, A.; Adam, G.; Golsch, D.; Adam, W.; Wagner, C.; Merzweiler, K.; Synthesis of 2,24-Diepicastasterone and 3,24-Diepicastasterone as Potential Brassinosteroid Metabolites of the Cockroach Periplaneta americana Collect. Czech. Chem. Commun. 67, 91-102, (2002) DOI: 10.1135/cccc20020091

Investigations of the metabolic conversion of the phytohormone 24-epicastasterone (1) in the cockroach Periplaneta americana (L.) required the synthesis of 2,24-diepicastasterone (4), 3,24-diepicastasterone (7b) and 2-dehydro-3,24-diepicastasterone (9) as reference standards. 2,24-Diepicastasterone (4) was synthesized from 2α,3α-epoxy derivative 2 as well as from the 2β,3β-epoxy-22,23-diol 3 by acid-catalyzed water addition to the epoxy function leading to the desired 2β,3α-trans functionality. 3,24-Diepicastasterone (7b) was prepared by NaBH4-reduction of the 3-oxo derivative 6. Upon deprotection conditions from the ketol acetonides 6 and 8 in both cases 2-dehydro-3,24-diepicastasterone (9) was obtained. The structure of 2,24-diepicastasterone (4) was confirmed by X-ray analysis.
Publications

Kolbe, A.; Fuchs, P.; Porzel, A.; Baumeister, U.; Kolbe, A.; Adam, G.; Synthesis and crystal structure of [26,27-2H6] 24-epi-cathasterone J. Chem. Soc., Perkin Trans. 1 2002, 2022-2027, (2002) DOI: 10.1039/B203323B

The first synthesis of [26,27-2H6]24-epi-cathasterone 8via (20S)-3β-acetoxy-6,6-(ethylenedioxy)-20-formyl-5α-pregnane 5 starting from stigmasterol is described. The aldehyde 5 was alkylated with lithium butyldimethyl-(E)-2,3-dimethyl[3,3,3,4,4,4-2H6]butenylaluminate 6 prepared from 3-[2H3]methyl[4,4,4-2H3]but-1-yne. The structure was determined using spectral data and X-ray crystallographic analysis.
Publications

Kolbe, A.; Kramell, R.; Porzel, A.; Schmidt, J.; Schneider, G.; Adam, G.; Syntheses of Dexamethasone Conjugates of the Phytohormones Gibberellin A3 and 24-Epicastasterone Collect. Czech. Chem. Commun. 67, 103-114, (2002) DOI: 10.1135/cccc20020103

The syntheses of N-[10-(9α-fluoro-11β,17α-dihydroxy-16α-methyl-3-oxoandrosta-1,4-diene-17β-carboxamido)decyl]gibberellamide (7) and 6-[({N-[10-(9α-fluoro-11β,17α-dihydroxy- 16α-methyl-3-oxoandrosta-1,4-diene-17β-carboxamido)decyl]carbamoyl}methoxy)imino]-24-epicastasterone (10) are described. [(Benzotriazol-1-yl)oxy]bis(pyrrolidin-1-yl)methylium hexafluorophosphate (HBPyU) was used as the coupling agent for the reaction of gibberellic acid as well as of 24-epicastasterone-O-(carboxymethyl)oxime with N-(10-aminodecyl)- 9α-fluoro-11β,17α-dihydroxy-16α-methyl-3-oxoandrosta-1,4-diene-17β-carboxamide (4). The gibberellic acid conjugate 7 was also synthesised by the coupling of succinimidyl gibberellate 6 with amine 4.
Publications

Anh, N. T. H.; Sung, T. V.; Wessjohann, L.; Adam, G.; The iridois and iridoid glycosid from the Rehmanuia glutinosa Rhizome Vietnam J. Chem. 40, 17-22, (2002)

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Publications

Anh, N. T. H.; Sung, T. V.; Wessjohann, L. A.; Adam, G.; Some hydroxycinnamic acid esters of phenylethyl alcohol glycosides from Rehmannia glutinosa Libosch Vietnam J. Chem. 40, 175-179, (2002)

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Publications

Bringmann, G.; Schlauer, J.; Rischer, H.; Wohlfarth, M.; Mühlbacher, J.; Buske, A.; Porzel, A.; Schmidt, J.; Adam, G.; Revised Structure of Antidesmone, an Unusual Alkaloid from Tropical Antidesma Plants (Euphorbiaceae) Tetrahedron 56, 3691-3695, (2000) DOI: 10.1016/S0040-4020(00)00289-1

The structure of antidesmone, an alkaloid from Antidesma membranaceum Müll. Arg. and A. venosum E. Mey. (Euphorbiaceae), was revised to be (S)-4,8-dioxo-3-methoxy-2-methyl-5-n-octyl-1,4,5,6,7,8-hexahydroquinoline [(S)-2], not the isoquinoline derivative 1, as assumed previously. The revision was initiated by biosynthetic feeding experiments of one of our groups.
Publications

Schmidt, J.; Richter, K.; Voigt, B.; Adam, G.; Metabolic Transformation of the Brassinosteroid 24-Epi-castasterone by the Cockroach Periplaneta americana Z. Naturforsch. C 55, 233-239, (2000) DOI: 10.1515/znc-2000-3-415

After feeding of 24-epi-castasterone to the cockroach Periplaneta americana an organspecific epimerization of the brassinosteroid to 2,24-depi-castasterone could be detected in female insects. The metabolite being observed only in the ovaries and not in the testes of the insect was identified by GC/MS in comparison with a synthesized authentic sample. Contrary, 24-epi-brassinolide is not metabolized in the sexual organs of Periplaneta americana. This is the first evidence of a metabolic transformation of a brassinosteroid in insects.
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

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).
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