Brunhilde Voigt

Secasterone, the first naturally occurring 2,3-epoxybrassinosteroid from Secale cereale

Abstract The new brassinosteroid secasterone, (22 R ,23 R ,24 S )-22,23-dihydroxy-2β,3β-epoxy-24-methyl-5α-cholestan-6-one, isolated from seeds of Secale cereale (rye) was identified by gas chromatography-mass spectral analysis. Secasterone represents the first naturally occurring brassinosteroid with a 2,3-epoxy function. Furthermore, the known brassinosteroids castasterone, 28-homocastasterone, 28-norcastasterone (brassinone), 6-deoxocastasterone, typhasterol and teasterone were identified from seeds of the same plant material.

2-deoxybrassinolide—A naturally occurring brassinosteroid from Apium graveolens

A new brassinosteroid was detected in seeds of Apium graveolens and it was shown to be 2-deoxybrassinolide by gas chromatography-mass spectral analysis and comparison with suitable reference compounds.

24-Epi-secasterone and 24-epi-castasterone from Lychnis viscaria seeds

The brassinosteroids 24-epi-castasterone and the hitherto unknown (22R, 23R, 24R)-22,23-dihydroxy-2β,3β-epoxy-24-methyl-5α-cholestan-6-one (24-epi-secasterone) could be identified from seeds of Lychnis viscaria (Caryophyllaceae). In the phytosterol fraction of the same plant material spinasterol was found as the main component.

Pregnane-type metabolites of brassinosteroids in cell suspension cultures of Ornithopus sativus

Abstract Exogenously applied 24- epi -castasterone and 24- epi -brassinolide are transformed in a multi-step metabolic process by cell suspension cultures of Ornithopus sativus to give 2α,3β,6β-trihydroxy-5α-pregnane-20-one and 2α,3β-dihydroxy-B-homo-7-oxa-5α-pregnane-6,20-dione, respectively, as the major metabolites. This is the first report concerning a catabolic side-chain degradation of brassinosteroids in plant material.

Regioselective oxyfunctionalization of brassinosteroids by methyl(trifluoromethyl)dioxirane: Synthesis of 25-hydroxy-brassinolide and 25-hydroxy-24-epibrassinolide by direct C-H insertion

Abstract The direct oxyfunctionalization of suitable brassinosteroid derivatives at position 25 using methyl(trifluoromethyl)dioxirane is reported. Whereas reaction with tetraacetyl brassinolide led after deprotection directly to the desired 25-hydroxy-brassinolide, in the (24R) series the 22,23-isopropylidenedioxy derivative has been shown to be a suitable precursor for the 25-hydroxylation leading to 25-hydroxy-24-epicastasterone and upon Baeyer-Villiger oxidation to 25-hydroxy-24-epibrassinolide, respectively.

Synthesis of 24-epiteasterone, 24-epityphasterol and their B-homo-6a-oxalactones from ergosterol

Abstract Continuing a programme directed toward the synthesis of biologically active analogues and potential biogeneric precursors of brassinosteroids the new members 24-epiteasterone (2) and 24- epityphasterol (7) as well as their corresponding lactones 2-deoxy-3,24-diepibrassinolide (3) and 2- deoxy-24-epibrassinolide (8) have been synthesized starting from ergosterol.

6-Deoxo-28-norcastasterone and 6-deoxo-24-epicastasterone —two new brassinosteroids from Ornithopus sativus

Two new brassinosteroids could be detected from shoots of Ornithopus sativus and identified as 6-deoxo-24-epicastasterone and 6-deoxo-28-norcastasterone by GC-MS. Furthermore, the known brassinosteroids castasterone, 24-epicastasterone and 6-deoxocastasterone were found in the same plant material.

Hydroxylation of the native brassinosteroids 24-epicastasterone and 24-epibrassinolide by the fungus Cunninghamella echinulata

24-Epicastasterone and 24-epibrassinolide, two naturally occurring phytohormones of the brassinosteroid type, were transformed by the fungus Cunninghamella echinulata to give the corresponding 12 beta-hydroxylated compounds. The structures of these compounds were determined by spectroscopic methods, especially heterocorrelated two-dimensional nuclear magnetic resonance investigations. In the rice lamina inclination test the 12 beta-hydroxylation lowered the bioactivity at 0.1 ppm to 10% in comparison with that of the corresponding parent hormones. The described hydroxylations represent the first biotransformations of native brassinosteroids.

Different oxidation pathways with various MnO2 types: Anomalous reaction with gibberellic acid

Abstract The oxidation of gibberellic acid ( 1 ) with neutral manganese dioxide prepared according to Mancera et al ., involves the free carboxylic group and gives rise to three anomalous products which correspond to oxidative decarboxylation ( 3,4 ) or lactonization ( 5 ). Optimal conditions for a normal allylic oxidation of 1 have been found using alkaline MnO 2 prepared according to Attenburrow et al . in acetone which gives yields of keto acid ( 2 ) up to 56%.

Labelling of biogenetic brassinosteroid precursors

A base catalyzed exchange procedure was employed to introduce tritium and deuterium, respectively, into enolizable positions of the steroidal ring system of several putative intermediates of 24R-type brassinosteroids. The method is suitable both for derivatives with protected hydroxyl groups as well as for non-protected compounds.