28506-81-2Relevant academic research and scientific papers
Enzymatic cyclization of dioxidosqualene to heterocyclic triterpenes
Shan, Hui,Segura, Michael J. R.,Wilson, William K.,Lodeiro, Silvia,Matsuda, Seiichi P. T.
, p. 18008 - 18009 (2005)
Oxidosqualene cyclases normally produce triterpenes from 2,3-(S)-oxidosqualene (OS) but also can cyclize its minor companion (3S,22S)-2,3:22,23-dioxidosqualene (DOS). We explored DOS cyclization in plant triterpene synthesis using a recombinant lupeol synthase (LUP1) heterologously expressed in yeast. Incubation of LUP1 with 3S,22S-DOS gave epoxydammaranes epimeric at C20 and a 17,24-epoxybaccharane in a 4:2:3 ratio. The products reflected a new mechanistic paradigm for DOS cyclization. The structures were determined by NMR and GC-MS, and recent errors in the epoxydammarane literature were rectified. Some DOS metabolites are likely candidates for regulating triterpenoid biosynthesis, while others may be precursors of saponin aglycones. Our in vivo experiments in yeast generated substantial amounts of DOS metabolites in a single enzymatic step, suggesting a seminal role for the DOS shunt pathway in the evolution of saponin synthesis. Quantum mechanical calculations revealed oxonium ion intermediates, whose reactivity altered the usual mechanistic patterns of triterpene synthesis. Further analysis indicated that the side chain of the epoxydammarenyl cation intermediate is in an extended conformation. The overall results establish new roles for DOS in triterpene synthesis and exemplify how organisms can increase the diversity of secondary metabolites without constructing new enzymes. Copyright
TRITERPENOIDS FROM THE LEAVES OF Betula lanata
Pokhilo, N. D.,Malinovskaya, G. V.,Makhan'kov, V. V.,Anufriev, V. F.,Uvarova, N. I.
, p. 368 - 372 (2007/10/02)
From the unsaponifiable fraction of an ethereal extract of the leaves of Betula lanata, in addition to 3-epiocotillol (I) we have isolated a new triterpene, 20(S),24(R)-epoxydammarane-3α,11α,25-triol (V) and also derivatives of it - the monoacetates at C-3 (II) and C-11 (III), and the monoketone at C-3 (IV).The structures of compounds (I-V) have been established on the basis of the results of physicochemical investigations.
