Diterpenes from the volatile oil of Dacrydium colensoi
作者:R. E. Corbett、R. A. J. Smith
DOI:10.1039/j39670000300
日期:——
(+)-Phyllocladene, (+)-rimuene, (+)-isokaurene, (–)-sandaracopimaradiene, and (+)-manoyl oxide have been identified in the diterpenoid fraction of the oil, which contains in addition a new diterpene alcohol, which has been shown to be (–)-8β-hydroxy-sandaracopimar-15-ene.
Biosynthesis of the oxygenated diterpene nezukol in the medicinal plant Isodon rubescens is catalyzed by a pair of diterpene synthases
作者:Kyle A. Pelot、Lynne M. Hagelthorn、J. Bennett Addison、Philipp Zerbe
DOI:10.1371/journal.pone.0176507
日期:——
Plants produce an immense diversity of natural products (i.e. secondary or specialized metabolites) that offer a rich source of known and potentially new pharmaceuticals and other desirable bioproducts. The Traditional Chinese Medicinal plant Isodon rubescens (Lamiaceae) contains an array of bioactive labdane-related diterpenoid natural products. Of these, the ent-kauranoid oridonin is the most prominent specialized metabolite that has been extensively studied for its potent antimicrobial and anticancer efficacy. Mining of a previously established transcriptome of I. rubescens leaf tissue identified seven diterpene synthase (diTPSs) candidates. Here we report the functional characterization of four I. rubescens diTPSs. IrTPS5 and IrTPS3 were identified as an ent-copalyl diphosphate (CPP) synthase and a (+)-CPP synthase, respectively. Distinct transcript abundance of IrTPS5 and the predicted ent-CPP synthase IrTPS1 suggested a role of IrTPS5 in specialized ent-kaurene metabolism possibly en route to oridonin. Nicotiana benthamiana co-expression assays demonstrated that IrTPS4 functions sequentially with IrTPS3 to form miltiradiene. In addition, IrTPS2 converted the IrTPS3 product (+)-CPP into the hydroxylated tricyclic diterpene nezukol not previously identified in I. rubescens. Metabolite profiling verified the presence of nezukol in I. rubescens leaf tissue. The proposed IrTPS2-catalyzed reaction mechanism proceeds via the common ionization of the diphosphate group of (+)-CPP, followed by formation of an intermediary pimar-15-en-8-yl+ carbocation and neutralization of the carbocation by water capture at C-8 to yield nezukol, as confirmed by nuclear magnetic resonance (NMR) analysis. Oxygenation activity is rare for the family of class I diTPSs and offers new catalysts for developing metabolic engineering platforms to produce a broader spectrum of bioactive diterpenoid natural products.
植物可产生种类繁多的天然产物(即次级或特殊代谢产物),为已知和潜在的新药及其他理想的生物制品提供了丰富的来源。中药植物 Isodon rubescens(灯心草科)含有一系列具有生物活性的唇形科二萜天然产物。其中,ent-kauranoid oridonin 是最突出的特殊代谢产物,因其强大的抗菌和抗癌功效而被广泛研究。对之前建立的 I. rubescens 叶组织转录组的挖掘发现了七个候选二萜合成酶(diTPSs)。在此,我们报告了四种 I. rubescens diTPSs 的功能特征。IrTPS5和IrTPS3分别被鉴定为ent-copalyl diphosphate(CPP)合成酶和(+)-CPP合成酶。IrTPS5和预测的ent-CPP合成酶IrTPS1不同的转录本丰度表明,IrTPS5可能在ent-kaurene的专门代谢中发挥作用。烟草本根共表达试验表明,IrTPS4 与 IrTPS3 依次发挥作用,形成米拉二烯。此外,IrTPS2 还能将 IrTPS3 产物 (+)-CPP 转化为羟基化的三环二萜 nezukol,而这是之前在 I. rubescens 中未发现的。代谢物分析证实了 I. rubescens 叶组织中存在 nezukol。经核磁共振(NMR)分析证实,IrTPS2 催化的反应机制是通过 (+)-CPP 的二磷酸基团的共同电离,然后形成中间的 pimar-15-en-8-yl+ 碳酸根,并通过 C-8 处的水捕获中和该碳位,生成 nezukol。氧合活性在 I 类 diTPSs 家族中是罕见的,为开发代谢工程平台提供了新的催化剂,从而生产出更多具有生物活性的二萜天然产物。
Blunt,J.W. et al., Australian Journal of Chemistry, 1977, vol. 30, p. 2015 - 2021
作者:Blunt,J.W. et al.
DOI:——
日期:——
Synthesis and the Iodine-Catalyzed Rearrangement of Isohibaene
作者:Masayuki Kitadani、Ken Ito、Akira Yoshikoshi
DOI:10.1246/bcsj.44.3431
日期:1971.12
A partial synthesis of isohibaene (VI) starting with nezukol (V) has been accomplished. It involves, as the key step, the intramolecular insertion reaction of a ketocarbene generated by cuprous oxide-catalyzed decomposition of diazoketone (XI) under irradiation. It has been found that isohibaene undergoes rearrangement into a mixture of phyllocladene (XIV) and isophyllocladene (XV) by iodine catalytically.