Confirmation of the stereochemistry of spiroviolene

• Yao Kong,
• Yuanning Liu,
• Kaibiao Wang,
• Tao Wang,
• Chen Wang,
• Ben Ai,
• Hongli Jia,
• Guohui Pan,
• Min Yin and
• Zhengren Xu

Beilstein J. Org. Chem. 2024, 20, 852–858, doi:10.3762/bjoc.20.77

• deoxyconidiogenol (4, Scheme 1A) by several terpene cyclases from fungus (PcCS, PchDS, PrDS) [15][16], which involves a 1,11-10,14 cyclization of GGPP, followed by 1,2-alkyl shift and a 2,10-cyclization, to give the key C3 cationic intermediate IM-1. A key 1,2-hydride shift from C2 to C3, which was observed in the

• spiroviolene and spirograterpene A therefore indicated that there must exist two terpene cyclases of different origins (Actinomycetes and Fungus) that were able to carry out similar chemical processes for the formation of the intriguing 5-5-5-5 tetracyclic ring system. Also, our study supports the proposed

• unified cyclization processes of spiroviolene and deoxyconidiogenol that bifurcate at the C6-cation intermediate IM-3 with a cyclopiane skeleton. Thus, further mutational studies of these related terpene cyclases would give us more insights into the complex cyclization processes. Structures of

Discovery and biosynthesis of bacterial drimane-type sesquiterpenoids from Streptomyces clavuligerus

• Dongxu Zhang,
• Wenyu Du,
• Xingming Pan,
• Xiaoxu Lin,
• Fang-Ru Li,
• Qingling Wang,
• Qian Yang,
• Hui-Min Xu and
• Liao-Bin Dong

Beilstein J. Org. Chem. 2024, 20, 815–822, doi:10.3762/bjoc.20.73

• , share the drimanyl scaffold, their biosynthetic pathways, particularly the terpene cyclases synthesizing the drimanyl structures, show substantial divergence from DMT pathways [21][30][31][32]. This fundamental difference in biosynthetic mechanisms serves to categorize DMSs and drimentines into distinct

• positions of drimenol (Figure 3d). However, the remaining two P450 enzymes, CavE and CavG, appear to be non-functional either in the native S. clavuligerus or heterologous expression systems. Given the detection of two terpene cyclases (CavC and CavF) and the exclusive DMTs generated, we also speculated

Genome mining of labdane-related diterpenoids: Discovery of the two-enzyme pathway leading to (−)-sandaracopimaradiene in the fungus Arthrinium sacchari

• Fumito Sato,
• Terutaka Sonohara,
• Shunta Fujiki,
• Akihiro Sugawara,
• Yohei Morishita,
• Taro Ozaki and
• Teigo Asai

Beilstein J. Org. Chem. 2024, 20, 714–720, doi:10.3762/bjoc.20.65

• underexplored family of natural products. In the biosynthesis of fungal LRDs, bifunctional terpene cyclases (TCs) consisting of αβγ domains are generally used to synthesize the polycyclic skeletones of LRDs. Herein, we conducted genome mining of LRDs in our fungal genome database and identified a unique pair of

• of TCs in fungi. Keywords: diterpenoids; fungi; genome mining; labdane; terpene cyclase; Introduction Terpenoids are a structurally diverse family of natural products, including more than 80,000 compounds [1]. In the biosynthesis of terpenoids, terpene cyclases (TCs) add structural diversity and

Production of non-natural 5-methylorsellinate-derived meroterpenoids in Aspergillus oryzae

• Jia Tang,
• Yixiang Zhang and
• Yudai Matsuda

Beilstein J. Org. Chem. 2024, 20, 638–644, doi:10.3762/bjoc.20.56

• and three additional biosynthetic enzymes for the formation of (6R,10′R)-epoxyfarnesyl-5-MOA methyl ester, which served as a non-native substrate for four terpene cyclases from DMOA-derived meroterpenoid pathways. As a result, we successfully generated six unnatural 5-MOA-derived meroterpenoid species

• , demonstrating the effectiveness of our approach in the generation of structural analogues of meroterpenoids. Keywords: biosynthesis; meroterpenoids; natural products; pathway engineering; terpene cyclases; Introduction Meroterpenoids are a class of natural products partially biosynthesized from a terpenoid

• polyketide portion [11][12][13][14]. One exception has been found in funiculolide biosynthesis, in which a 5-MOA-derived phthalide undergoes dearomatizing prenylation catalyzed by the UbiA-like prenyltransferase FncB (Figure 1B) [15]. In addition to prenyltransferases, transmembrane terpene cyclases play a

Recent developments in the engineered biosynthesis of fungal meroterpenoids

• Zhiyang Quan and
• Takayoshi Awakawa

Beilstein J. Org. Chem. 2024, 20, 578–588, doi:10.3762/bjoc.20.50

• mutagenesis of key enzymes, including terpene cyclases and α-ketoglutarate (αKG)-dependent dioxygenases, that contribute to the structural diversity. Notable progress in genome sequencing has led to the discovery of many novel genes encoding these enzymes, while continued efforts in X-ray crystallographic

• for the design of biosynthetic machineries to produce a variety of bioactive meroterpenoids. Keywords: αKG-dependent dioxygenases; enzyme engineering; fungal meroterpenoids; synthetic biology; terpene cyclases; Introduction Meroterpenoids are complex natural products with intricate skeletal

• biosynthesis of bioactive compounds with still greater skeletal diversity. Conclusion In summary, many novel terpene cyclases and αKG-dependent dioxygenases were discovered by recent developments in genome mining approaches. Unique meroterpenoids have been generated by integrating these enzymes into

Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

Navigating and expanding the roadmap of natural product genome mining tools

• Friederike Biermann,
• Sebastian L. Wenski and
• Eric J. N. Helfrich

Beilstein J. Org. Chem. 2022, 18, 1656–1671, doi:10.3762/bjoc.18.178

• , terpene cyclases generate the oftentimes multicyclic, hydrocarbon scaffold via a carbocation-mediated cascade reaction [30]. Terpene cyclases are obligatory components of canonical terpene pathways and are used to identify terpene BGCs (Figure 3B) [30][31]. RiPPs, on the other hand, lack genes that are

Understanding the role of active site residues in CotB2 catalysis using a cluster model

• Keren Raz,
• Ronja Driller,
• Thomas Brück,
• Bernhard Loll and
• Dan T. Major

Beilstein J. Org. Chem. 2020, 16, 50–59, doi:10.3762/bjoc.16.7

• , Dept. of Chemistry, Technical University of Munich (TUM), Lichtenbergstr. 4, 85748 Garching, Germany 10.3762/bjoc.16.7 Abstract Terpene cyclases are responsible for the initial cyclization cascade in the multistep synthesis of a large number of terpenes. CotB2 is a diterpene cyclase from Streptomyces

• different cellular compartments [1][2]. More specifically, the enigmatic class of terpene cyclases is responsible for converting linear aliphatic oligoprenyl diphosphates into various chemically complex macrocyclic products. The resulting terpene scaffolds and their functionalized terpenoid analogues

• crystal structure of a diterpene cyclase was reported by Christianson and co-workers [22]. These structures, in conjunction with extensive biochemical work [10][13][14][23], have contributed to the understanding of mechanistic details of terpene cyclases and facilitated rational enzyme design [24

Bacterial terpene biosynthesis: challenges and opportunities for pathway engineering

• Eric J. N. Helfrich,
• Geng-Min Lin,
• Christopher A. Voigt and
• Jon Clardy

Beilstein J. Org. Chem. 2019, 15, 2889–2906, doi:10.3762/bjoc.15.283

• different precursors and enzymes, and different organisms utilize either or both pathways. A typical textbook description then divides terpene biosynthesis into two phases (Figure 4): 1) hydrocarbon backbone assembly and cyclization catalyzed by oligoprenyl synthetases and terpene cyclases (terpene

•  6b) [80]. Despite efforts to characterize individual terpene cyclases and their modes of cyclization, no biosynthetic rules have so far been deduced that can be applied to a broad range of unrelated terpene cyclases. Phase 2) terpene scaffold functionalization Tailoring enzymes are important elements

• analogy to nature’s biosynthetic strategies outlined above, cationic, Diels–Alder, oxidative, and radical cyclization strategies have been successfully applied in total syntheses of terpenoids [53]. In addition, chemists are currently creatively exploring means to mimic classical terpene cyclases and

Inherent atomic mobility changes in carbocation intermediates during the sesterterpene cyclization cascade

• Hajime Sato,
• Takaaki Mitsuhashi,
• Mami Yamazaki,
• Ikuro Abe and
• Masanobu Uchiyama

Beilstein J. Org. Chem. 2019, 15, 1890–1897, doi:10.3762/bjoc.15.184

• terpene cyclase active site [3][5][6]. Although many terpene cyclases are known [6][7][8][9][10], it is still challenging to identify the precise initial conformation of the oligoprenyl diphosphate substrate in the active site, even by X-ray crystal structure determination. This is because the substrate

• ], and it appears that inherent reactivity [17] is in good accordance with the experimental outcome. This may mean that terpene cyclases do not tightly regulate the cyclization reaction steps once the carbocation is generated. Therefore, we considered that key regions of GFPP that control the fit of the

• affinity for the enzyme, and this might be relevant to substrate release. Few X-ray crystal structures of terpene cyclases are available [7][8], so we believe inherent mobility analysis will be useful to predict the mechanism of conformational preorganization of the substrate to achieve different

Herpetopanone, a diterpene from Herpetosiphon aurantiacus discovered by isotope labeling

• Xinli Pan,
• Nicole Domin,
• Sebastian Schieferdecker,
• Hirokazu Kage,
• Martin Roth and
• Markus Nett

Beilstein J. Org. Chem. 2017, 13, 2458–2465, doi:10.3762/bjoc.13.242

• numerous bacterial terpene cyclase genes [2][3]. Both in vitro and in vivo approaches involving recombinant enzymes are commonly pursued for their functional characterization [4]. Care must be taken, however, in interpreting the results of these analyses, as the products of terpene cyclases are often

• . aurantiacus 114-95T features four genes coding for putative terpene cyclases, i.e., Haur_2145, Haur_2987, Haur_2988, and Haur_4149. While the class II cyclase Haur_2145 had already been associated with the production of the terpenoid O-methylkolavelool [17], the products of the other three enzymes have not

Opportunities and challenges for the sustainable production of structurally complex diterpenoids in recombinant microbial systems

• Katarina Kemper,
• Max Hirte,
• Markus Reinbold,
• Monika Fuchs and
• Thomas Brück

Beilstein J. Org. Chem. 2017, 13, 845–854, doi:10.3762/bjoc.13.85

• synthases are classed according to their intron/exon pattern [47] and their diverse reaction initiation mechanisms [48]. Genomic analyses of plant terpene synthases by Trapp and co-workers [47] revealed general organization of 12–14 introns for Class I terpene cyclases, 9 introns for Class II and 6 introns

A detailed view on 1,8-cineol biosynthesis by Streptomyces clavuligerus

• Jan Rinkel,
• Patrick Rabe,
• Laura zur Horst and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2016, 12, 2317–2324, doi:10.3762/bjoc.12.225

• and achiral precursors such as geranyl diphosphate (GPP, monoterpenes), farnesyl diphosphate (FPP, sesquiterpenes) and geranylgeranyl diphosphate (GGPP, diterpenes). Terpene cyclases (type I) contain a trinuclear (Mg2+)3 cluster in their active site that is stabilised by binding to several highly

• monooxygenases and acyl transferases [12][13]. Very few cases are known in which terpene cyclases generate an achiral product as exemplified by the monoterpene 1,8-cineol (eucalyptol, 1) and the sesquiterpenes germacrene B (2) and α-humulene (3) (Figure 1). A direct 1,6-cyclisation of the monoterpene precursor

• either enantiomer of the α-terpinyl cation (6, Scheme 1). Isotopic labelling experiments currently experience a revival [15] and are a very powerful method to follow the enzyme mechanisms of terpene cyclases [16][17][18][19][20][21][22][23][24] including the stereochemical courses of the cyclisation

Mechanistic investigations on six bacterial terpene cyclases

• Patrick Rabe,
• Thomas Schmitz and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2016, 12, 1839–1850, doi:10.3762/bjoc.12.173

• terpene cyclases were characterised by one- and two-dimensional NMR spectroscopic methods, allowing for a full structure elucidation. The absolute configurations of four terpenes were determined based on their optical rotary powers. Incubation experiments with 13C-labelled isotopomers of FPP in buffers

• containing water or deuterium oxide allowed for detailed insights into the cyclisation mechanisms of the bacterial terpene cyclases. Keywords: absolute configuration; biosynthesis; enzyme mechanisms; structure elucidation; terpenes; Introduction Terpenes are structurally fascinating natural products with

• terpene cyclases from bacterial genomes. Altogether, a number of ca. 1000 terpene cyclase genes are found in the genomes of sequenced bacteria [10], and about 50 bacterial terpene cyclases have so far been characterised for their products [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27

The EIMS fragmentation mechanisms of the sesquiterpenes corvol ethers A and B, epi-cubebol and isodauc-8-en-11-ol

• Patrick Rabe and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2016, 12, 1380–1394, doi:10.3762/bjoc.12.132

• bacterial terpene cyclases corvol ether synthase from Kitasatospora setae, the epi-cubebol synthase from Streptosporangium roseum, and the isodauc-8-en-11-ol synthase from Streptomyces venezuelae. The enzyme products were analysed by GC–MS and GC–QTOF MS2 and the obtained data were used to delineate the

• -methylisoborneol biosynthetic pathway by comparing the mass spectra of the methylated compounds to their non-methylated analogs [11]. Higher terpenes such as sesqui- and diterpenes, as being produced by terpene cyclases from oligoprenyl diphosphates, are usually (poly)cyclic compounds with different ring sizes

• isodauc-8-en-11-ol made by terpene cyclases from Streptosporangium roseum [19][20] and from Streptomyces venezuelae [21]. Results and Discussion To investigate the EIMS fragmentation mechanisms for the two sesquiterpene ethers corvol ether A (1) and corvol ether B (2), and for the sesquiterpene alcohols

Recent highlights in biosynthesis research using stable isotopes

• Jan Rinkel and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2015, 11, 2493–2508, doi:10.3762/bjoc.11.271

• skeletons (Figure 6). The fascination of terpene biosynthesis arises from the complexity and variety of carbon scaffolds, terpene cyclases are able to build up using few linear oligoprenyl diphosphate precursors. This promotes investigations using isotopically labeled compounds both on acetate- and

• assembly of natural product. Also the kinetic isotope effect can be used to probe mechanistic proposals, as elegantly shown for the pentalenene (65) cyclization mechanism. Pentalenene synthase is one of the first and best investigated bacterial terpene cyclases both structurally [70] and functionally [71

[²H₂₆]-1-epi-Cubenol, a completely deuterated natural product from Streptomyces griseus

• Christian A. Citron and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2013, 9, 2841–2845, doi:10.3762/bjoc.9.319

• ; terpenes; Introduction The actinomycete Streptomyces griseus is a producer of three terpenes, 2-methylisoborneol (2-MIB, 1), (+)-caryolan-1-ol (2), and (+)-1-epi-cubenol (3, Figure 1). The biosynthesis of 2 and 3 requires the action of well characterized terpene cyclases [1][2], while the biosynthesis of