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Diverged Plant Terpene Synthases Reroute the Carbocation Cyclization Path towards the Formation of Unprecedented 6/11/5 and 6/6/7/5 Sesterterpene Scaffolds
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Dr. Ancheng C. Huang Dr. Young J. Hong Dr. Andrew D. Bond Prof. Dr. Dean J. Tantillo Prof. Anne Osbourn 《Angewandte Chemie (International ed. in English)》2018,57(5):1291-1295
Sesterterpenoids are a relatively rare class of plant terpenes. Sesterterpene synthase (STS)‐mediated cyclization of the linear C25 isoprenoid precursor geranylfarnesyl diphosphate (GFPP) defines sesterterpene scaffolds. So far only a very limited number of STSs have been characterized. The discovery of three new plant STSs is reported that produce a suite of sesterterpenes with unprecedented 6/11/5 and 6/6/7/5 fused ring systems when transiently co‐expressed with a GFPP synthase in Nicotiana benthamiana. Structural elucidation, feeding experiments, and quantum chemical calculations suggest that these STSs catalyze an unusual cyclization path involving reprotonation, intramolecular 1,6 proton transfer, and concerted but asynchronous bicyclization events. The cyclization is diverted from those catalyzed by the characterized plant STSs by forming unified 15/5 bicyclic sesterterpene intermediates. Mutagenesis further revealed a conserved amino acid residue implicated in reprotonation. 相似文献
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Introduction In the previous papers, we reported the isolation and structural elucidation of eight 20,24-bishomoscalarane sesterterpenes from the sponge Phyllospongia foliascens collected from Xisha Islands. As a result of our continual investigation of the same sponge 相似文献
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A convergent synthesis provided a C25 and a C35 oxidopolyprene in which a farnesyl C15 unit is connected in a head-to-head fashion to a geranyl C10 or a geranylgeranyl C20 unit. When incubated with recombinant β-amyrin synthase from Pisum sativum the C25 oxidopolyprene was enzymatically converted to an unnatural novel tetracyclic sesterterpene, while the C35 analogue did not afford any cyclization product. 相似文献
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Khadijah A. Jabal Hossam M. Abdallah Gamal A. Mohamed Ibrahim A. Shehata Mohammad Y. Alfaifi Serag Eldin I. Elbehairi 《Natural product research》2020,34(15):2167-2172
AbstractThe CHCl3 fraction of MeOH extract of Periploca somaliensis (family Asclepiadaceae) fruits afforded a new scalarane sesterterpene, namely perisomalien A (1), along with lupeol acetate (2), β-amyrin (3), cycloart-23Z-ene-3β,25-diol (4), and β-sitosterol-3-O-β-D-glucopyranoside (5). Their chemical structures were established by various spectroscopic analyses, in addition to comparison with the formerly reported data. Moreover, the cytotoxic activity of these metabolites was assessed towards MCF-7, HepG2, and HCT-116 tumour cell lines using sulforhodamine B (SRB) assay. Compound 4 showed the most potent cytotoxic profile with IC50 9.0?µM towards MCF-7, compared to doxorubicin (IC50 0.18?µM). Also, 1 and 4 possessed the most potent effect towards HepG2 with IC50s 26.7 and 25.9?μM, respectively. In addition, all tested compounds showed cytotoxic effects with IC50 values ranging from 19.9 to 39.3?µM against HCT-116. 相似文献
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