Origin of structural diversity in natural triterpenes:: Direct synthesis of seco-triterpene skeletons by oxidosqualene cyclase
Origin of structural diversity in natural triterpenes:: Direct synthesis of seco-triterpene skeletons by oxidosqualene cyclase
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DOI：
10.1021/ja066873w
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发表时间：
2007-02-07
影响因子：
15
通讯作者：
Ebizuka, Yutaka
中科院分区：
文献类型：
--
作者：
Shibuya, Masaaki;Xiang, Ting;Ebizuka, Yutaka
At 1g 78500，氧化角鲨烯环化酶（OSC）的同源物之一，从拟南芥，表达羊毛甾醇环化酶缺陷的酵母菌株和产物进行了分析。除了已知的三萜类化合物外，还发现该OSC产生了两种新的三萜类化合物，其结构通过NMR和MS分析确定。新的三萜是C-环-开环-β-香树脂醇（1）和C-环-开环-α-香树脂醇（2），并分别命名为β-开环-香树脂醇和α-开环-香树脂醇。β-开环-香树脂素是通过C8和C14之间的键断裂由油烷基阳离子产生的，α-开环-香树脂素是以相同的方式由熊烷基阳离子产生的。同时，利用A. thaliana的研究表明，OSC不仅催化碳-碳键的形成和Wagner-Meerwein重排，而且还裂解阳离子中间体中的预形成的环系统。基于这些信息，提出了通过OSC直接生产其他天然开环三萜。
At1g78500, one of the oxidosqualene cyclase (OSC) homologues from Arabidopsis thaliana, was expressed in a lanosterol synthase-deficient yeast strain and the products were analyzed. In addition to the known triterpenes, this OSC was found to produce two new triterpenes, the structures of which were determined by NMR and MS analyses. The new triterpenes are C-ring-seco-beta-amyrin (1) and C-ring-seco-alpha-amyrin (2) and named beta-seco-amyrin and alpha-seco-amyrin, respectively. beta-seco-Amyrin is produced from the oleanyl cation through bond cleavage between C8 and C14, and alpha-seco-amyrin is produced from the ursanyl cation in the same manner. Together with Grob fragmentation catalyzed by another OSC (marneral synthase) from A. thaliana, the formation of seco-amyrins by this OSC revealed that OSCs not only catalyze carbon-carbon bond formations and Wagner-Meerwein rearrangements but also cleave preformed ring systems in cationic intermediates. Based on this information, direct production of other natural seco-triterpenes by OSCs is proposed.