Enzymatic Cyclization of Dioxidosqualene to Heterocyclic Triterpenes
作者:Hui Shan、Michael J. R. Segura、William K. Wilson、Silvia Lodeiro、Seiichi P. T. Matsuda
DOI:10.1021/ja055822g
日期:2005.12.1
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
氧化角鲨烯环化酶通常从 2,3-(S)-氧化角鲨烯 (OS) 产生三萜,但也可以环化其次要伙伴 (3S,22S)-2,3:22,23-二氧化角鲨烯 (DOS)。我们使用在酵母中异源表达的重组羽扇豆醇合酶 (LUP1) 探索了植物三萜合成中的 DOS 环化。LUP1 与 3S,22S-DOS 的孵育在 C20 处产生环氧达玛烷差向异构体和 17,24-环氧巴炭烷,比例为 4:2:3。这些产品反映了 DOS 环化的新机制范例。结构由 NMR 和 GC-MS 确定,并纠正了环氧达玛烷文献中最近的错误。一些 DOS 代谢物可能是调节三萜生物合成的候选物,而另一些可能是皂苷苷元的前体。我们在酵母中的体内实验在单个酶促步骤中产生了大量的 DOS 代谢物,表明 DOS 分流途径在皂苷合成进化中的重要作用。量子力学计算揭示了氧鎓离子中间体,其反应性改变了三萜合成的通常机制模式。进一步分析表明,环氧丹马烯基
Onocerin Biosynthesis Requires Two Highly Dedicated Triterpene Cyclases in a Fern<i>Lycopodium clavatum</i>
Cyclize from both ends: A symmetrical triterpenoid α‐onocerin was found to requiretwo enzymes for its biosynthesis. Both exhibited unprecedented substrate specificity among oxidosqualene cyclases, one specific to dioxidosqualene and the other to partially cyclized pre‐α‐onocerin.
Promiscuous Oxidosqualene Cyclases from <i>Neoalsomitra integrifoliola</i> Catalyzing the Formation of Tetracyclic, Pentacyclic, and Heterocyclic Triterpenes
cyclases (NiOSC1–NiOSC6) from Neoalsomitra integrifoliola were characterized for the biosynthesis of diverse triterpene scaffolds, including tetracyclic and pentacyclic triterpenesfrom the 2,3-oxidosqualene (1) and oxacyclic triterpenesfrom the 2,3:22,23-dioxidosqualene (2). NiOSC1 showed high efficiency in the production of naturally rare (20R)-epimers of oxacyclic triterpenes. Mutagenesis results revealed
来自Neoalsomitra integrifoliola的六种氧化角鲨烯环化酶 ( Ni OSC1– Ni OSC6) 被表征用于生物合成多种三萜支架,包括来自 2,3-氧化角鲨烯 ( 1 ) 的四环和五环三萜和来自 2,3:22,23 的氧杂环三萜-二氧化角鲨烯( 2 )。 Ni OSC1 在生产天然稀有的氧杂环三萜 (20 R )-差向异构体方面表现出高效率。诱变结果表明,与野生型相比, Ni OSC1-F731G 突变体显着增加了 (20 R )-差向异构体的产量。同源建模和分子对接阐明了环氧化物加成步骤中 (20 R )-构型的起源。
Direct regio- and stereoselective synthesis of squalene 2,3;22,23-dioxide using dioxiranes
作者:Lucia D’Accolti、Cosimo Annese、Caterina Fusco
DOI:10.1016/j.tetlet.2005.10.022
日期:2005.12
Dimethyldioxirane (1a) and its trifluoro analog (1b) were employed to achieve selectively the direct transformation of squalene 2,3(S)-oxide and of squalene 2,3(R)-oxide into the corresponding 2,3(S);22(S),23-dioxide and 2,3(R);22(R),23-dioxide, respectively. These transformations were found to occur with convenient regio- and diastereoselectivity, providing easy access to the valuable dioxides metabolites
Simple Total Synthesis of the Pentacyclic <i>C</i><i><sub>s</sub></i>-Symmetric Structure Attributed to the Squalenoid Glabrescol and Three <i>C</i><i><sub>s</sub></i>-Symmetric Diastereomers Compel Structural Revision