Biosynthesis of kelsoene and prespatane in cultured cells of the liverwortPtychanthus striatus

Citation
K. Nabeta et al., Biosynthesis of kelsoene and prespatane in cultured cells of the liverwortPtychanthus striatus, J CHEM S P1, (16), 2000, pp. 2703-2708
Citations number
16
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Chemistry & Analysis","Organic Chemistry/Polymer Science
Journal title
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 1
ISSN journal
1470-4358 → ACNP
Issue
16
Year of publication
2000
Pages
2703 - 2708
Database
ISI
SICI code
1470-4358(2000):16<2703:BOKAPI>2.0.ZU;2-F
Abstract
Biosynthesis of the unusual sesquiterpenes, (+)-kelsoene and (-)-prespatane , that accumulate in the cultured cells of the liverwort Ptychanthus striat us was investigated. A mixture of (+)- and (-)-alloaromadendrene was isolat ed from a variety of unidentified sesquiterpenes from cultured cells. Howev er, the (-)-isomer, which is thought to be an immediate precursor to kelsoe ne, was present only as a minor component [a ratio of (-)-isomer to (+)-iso mer of 1:25]. When the cells were incubated with a higher dosage (1.0 mmol) of mevalonate (MVA, 3,5-dihydroxy-3-methylvalerate) under heterotrophic co nditions or with a normal dosage (0.5 mmol) under photoautotrophic conditio ns, the H-2- and C-13-labels from H-2- and C-13-MVA were incorporated into the sesquiterpenes at an extremely high level (30 to 40 and 46 atom% excess , respectively). Labelling patterns of the biosynthetically H-2- or C-13-la belled kelsoene and prespatane were determined by GLC-MS and H-2- and C-13- NMR analyses. The labelling pattern of the kelsoene demonstrates the random ization of the H-2- and C-13-labels between the isopropenylmethyl and the m ethylene groups, with loss of one H-1 proton of farnesyl diphosphate (FPP, farnesyl=3,7,11-trimethyldodeca- 2,6,10-trienyl), suggesting that kelsoene is biosynthesized from a germacradienyl cation with 7R configuration by mea ns of a (-)-alloaromadendranyl cation. Randomization of the labels between the isopropenylmethyl and the methylene and loss of one H-1 proton of FPP w ere also observed in H-2- and C-13-labelled prespatane. Thus, prespatane is postulated to be biosynthesized from a (7S)-germacradienyl cation by means of a guaianyl cation. During the third cyclization of the guaianyl cation, one proton at the C-1 position of FPP was lost.