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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
The leaves of Luvunga sarmentosa (Bl.) Kurz. yielded eight apotirucallane triterpenoids named luvungins A–G, and 1α-acetoxyluvungin A. Characteristic of the structure are the seven-membered lactone-ring A, the α-hydroxyl or α-acetoxyl group at C-7 and an oxygen bridge in the side chain giving five-, six- or seven-membered rings, respectively. Because of a hemiacetal function at C-21, luvungin C occurred as a mixture of 21-epimers. The structures have been elucidated on the basis of MS and NMR spectral data. In addition, two known coumarins ostruthin (6-geranyl-7-hydroxycoumarin) and 8-geranyl-7-hydroxycoumarin as well as five known triterpenes friedelin, flindissone, melianone, niloticin and limonin were isolated.The leaves of Luvunga sarmentosa (Bl.) Kurz. yielded eight apotirucallane triterpenoids named luvungins A–G and 1α-acetoxyluvungin A. Characteristic for the luvungins were the seven-membered lactone-ring A, the α-hydroxyl or α-acetoxyl group at C-7 and an oxygen bridge in the side chain giving five-, six- or seven-membered rings.
Publications
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
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.