Functional characterisation of twelve terpene synthases from actinobacteria

• Anuj K. Chhalodia,
• Houchao Xu,
• Georges B. Tabekoueng,
• Binbin Gu,
• Kizerbo A. Taizoumbe,
• Lukas Lauterbach and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2023, 19, 1386–1398, doi:10.3762/bjoc.19.100

• identified by GC–MS. The characterised enzymes include a new epi-isozizaene synthase with monoterpene synthase side activity, a 7-epi-α-eudesmol synthase that also produces hedycaryol and germacrene A, and four more sesquiterpene synthases that produce mixtures of hedycaryol and germacrene A. Three

• Streptomyces pristinaespiralis [26], spiroviolene synthase from Streptomyces violens [27], micromonocyclol synthase from Micromonospora marina [28], α-amorphene synthase from Streptomyces viridochromogenes [29][30], epi-cubenol synthase from S. griseus [31], germacrene A synthase from M. marina [32], and 7-epi

• ) and the NSE triad (225NDIHSYEKE, Figure S12, Supporting Information File 1) and its closest characterised relative is with 32% identity the germacrene A synthase from M. marina [32]. The incubation with GPP resulted in minor amounts of acyclic compounds (myrcene, ocimene, linalool), while FPP gave a

Germacrene B – a central intermediate in sesquiterpene biosynthesis

• Houchao Xu and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2023, 19, 186–203, doi:10.3762/bjoc.19.18

• potentially arise from the achiral sesquiterpene hydrocarbon germacrene B. Not only compounds isolated from natural sources, but also synthetic compounds are dicussed, with the aim to give a rationale for the structural assignment for each compound. A total number of 64 compounds is presented, with 131 cited

• references. Keywords: biosynthesis; configuration determination; germacrene B; structure elucidation; terpenes; Introduction Terpenoids constitute the largest class of natural products with ca. 100,000 known compounds. Biosynthetically, all terpenoids are derived from only a few acyclic precursors

• - (selinane) or 5-7-bicyclic (guaiane) sesquiterpenes. We have recently summarised the accumulated knowledge about sesquiterpenes derived from germacrene A (2) [12] and hedycaryol (3) [13]. Now we wish to provide a review on the known chemical space of sesquiterpenes derived from germacrene B (1) (Scheme 2

The enzyme mechanism of patchoulol synthase

• Houchao Xu,
• Bernd Goldfuss,
• Gregor Schnakenburg and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2022, 18, 13–24, doi:10.3762/bjoc.18.2

• results from these experiments are contradictory. The present work reports on a reinvestigation of patchoulol biosynthesis by isotopic labelling experiments and computational chemistry. The results are in favour of a pathway through the neutral intermediates germacrene A and α-bulnesene that are both

• compound 3 and several biogenetically related terpene hydrocarbons including α-patchoulene (4), β-patchoulene (5), α-bulnesene (6) and α-guaiene (7) (Figure 1) [7]. The enzyme was subsequently made available by cDNA gene cloning, revealing germacrene A (8), α-humulene (9), (E)-β-caryophyllene (10

• . (Scheme 2) [10] DFT calculations have been performed previously by us as part of a general study on guaiane sesquiterpenes from germacrene A (8) [29]. After reprotonation of the neutral intermediate 6 to F the next cyclisation to G and Wagner–Meerwein rearrangement to D can be realised with low TS

Volatile emission and biosynthesis in endophytic fungi colonizing black poplar leaves

• Christin Walther,
• Pamela Baumann,
• Katrin Luck,
• Beate Rothe,
• Peter H. W. Biedermann,
• Jonathan Gershenzon,
• Tobias G. Köllner and
• Sybille B. Unsicker

Beilstein J. Org. Chem. 2021, 17, 1698–1711, doi:10.3762/bjoc.17.118

• culture and showed that both species are able to produce sesquiterpenes like (E)-β-farnesene (2), α- and β-chamigrene (4), and germacrene D [41]. In general, terpenes are derived from the five-carbon intermediates dimethylallyl diphosphate (DMAPP) and isopentenyl diphosphate (IPP), which are both produced

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

• pyrophosphate synthase, and GFPP geranylfarnesyl pyrophosphate. Mechanisms for type I, type II, and type II/type I tandem terpene cyclases. a) Tail-to-head class I germacrene A (13) cyclase. b) Head-to-tail type II brasilicardin (14) cyclase. c) Type II ent-copalyl diphosphate (15) synthase and type I ent

Harnessing enzyme plasticity for the synthesis of oxygenated sesquiterpenoids

• Melodi Demiray,
• David J. Miller and
• Rudolf K. Allemann

Beilstein J. Org. Chem. 2019, 15, 2184–2190, doi:10.3762/bjoc.15.215

• (E)-β-farnesene may be of significant benefit in agriculture [24]. While (S)-germacrene D is a highly volatile but unstable olfactory signal that repels invertebrate arthropod pests (insects, ticks, mites) that affect humans and livestock as well as arable crops, (S)-14,15-dimethylgermacrene D acts

Analysis of sesquiterpene hydrocarbons in grape berry exocarp (Vitis vinifera L.) using in vivo-labeling and comprehensive two-dimensional gas chromatography–mass spectrometry (GC×GC–MS)

• Philipp P. Könen and
• Matthias Wüst

Beilstein J. Org. Chem. 2019, 15, 1945–1961, doi:10.3762/bjoc.15.190

• -copaene, β-copaene, α-cubebene, β-cubebene and the bicyclic δ-cadinene were biosynthesized via (S)-(−)-germacrene D rather than via (R)-(+)-germacrene D as intermediate. Keywords: biosynthesis; deuterium labeling; germacrene; HS-SPME; terpenes; TOF–MS; Introduction The aroma profile of grape berries at

• partially labeled sesquiterpenes, as Supporting Information File 2 shows using compound 10 as an example. Sesquiterpene biosynthesis Biosynthesis of sesquiterpene hydrocarbons via (S)-(−)-germacrene D The biosynthetic pathways for the formation of δ-cadinene, α-copaene, β-copaene, α-cubebene and β-cubebene

• via germacrene D in the legume Medicago truncatula have been previously reported by Boland and Garms [29]. The formation of the mentioned sesquiterpenes could a priori take place via farnesyl pyrophosphate (FPP) as well as via (S)- and (R)-nerolidyl pyrophosphate (NPP) (Scheme 1). Both enantiomers of

Volatiles from three genome sequenced fungi from the genus Aspergillus

• Jeroen S. Dickschat,
• Ersin Celik and
• Nelson L. Brock

Beilstein J. Org. Chem. 2018, 14, 900–910, doi:10.3762/bjoc.14.77

•  2 and Scheme 4). In addition, small amounts of the sesquiterpenes β-elemene (21a), germacrene D (22), β-ylangene (23) and its stereoisomer β-copaene (24) were found. All these sesquiterpenes require a 1,10-cyclisation of FPP to the (E,E)-germacradienyl cation (N). Its deprotonation leads to

• germacrene A (21) that is known to undergo a Cope rearrangement to 21a caused by the thermal impact during GC–MS analysis [38]. A 1,3-hydride shift transforms N into O that yields 22 by loss of a proton. Its reprotonation can induce a second cyclisation event via R and S to 24, or with a different

• to fungal germacrene D synthases [40] (Figure S1 in Supporting Information File 1) and are good candidates for the formation of 22 and the compounds derived from it in A. kawachi. Aspergillus clavatus The headspace extracts from A. clavatus contained small amounts of oct-1-en-3-ol (1) and terpenes

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

• includes α-cadinol, originates from germacrene D [7][23]. In the case of 1, an analogous pathway can be postulated, which is depicted in Figure 4. The biosynthesis would hence start with geranylgeranyl pyrophosphate (GGPP). Upon ionization, the double bond nearest the diphosphate can adopt a Z

Are boat transition states likely to occur in Cope rearrangements? A DFT study of the biogenesis of germacranes

• José Enrique Barquera-Lozada and
• Gabriel Cuevas

Beilstein J. Org. Chem. 2017, 13, 1969–1976, doi:10.3762/bjoc.13.192

• predict the conformation of a germacrene. Interestingly, the (Z,E)-germacranes are significantly more stable than (E,E)-germacranes. Then, cis/trans isomerization can only happen in one way, (E,E)-germacranes → (Z,E)-germacranes. Moreover, this isomerization cannot be thermally activated because of the

18-Hydroxydolabella-3,7-diene synthase – a diterpene synthase from Chitinophaga pinensis

• Jeroen S. Dickschat,
• Jan Rinkel,
• Patrick Rabe,
• Arman Beyraghdar Kashkooli and
• Harro J. Bouwmeester

Beilstein J. Org. Chem. 2017, 13, 1770–1780, doi:10.3762/bjoc.13.171

• previously reported to have germacrene A synthase activity during heterologous expression in Escherichia coli, was identified by extensive NMR-spectroscopic methods as 18-hydroxydolabella-3,7-diene. The absolute configuration of this diterpene alcohol and the stereochemical course of the terpene synthase

• production of volatile terpenes by this bacterium that can be detected in headspace extracts [17][18]. In one of these previous reports [17] we have described a terpene synthase from Chitinophaga pinensis DSM 2588 (accession number WP_012789469) as a sesquiterpene synthase for germacrene A (1), which was

• diterpene synthase from C. pinensis. Conclusion In this study we have reinvestigated a terpene synthase from Chitinophaga pinensis that was previously characterised as germacrene A synthase by heterologous expression in E. coli. While this result could be reproduced during the course of the present study

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

• 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

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

• . Heterologous expression of a third terpene synthase from Streptosporangium roseum DSM 43021 (accession number WP_043653400) and its incubation with FPP yielded the sesquiterpene alcohol 3, identified as 4-epi-cubebol by GC–MS, and minor amounts of cubebol, germacrene D-4-ol and δ-cadinene (Figure S1

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

• attack of water gives the neutral intermediate germacrene D-4-ol (39). Reprotonation induces the formation of the bicyclic system 40, which can rearrange via two sequential 1,2-hydride shifts to the cation 41. The attack of the hydroxy function and either a 1,2-hydride shift or a Wagner–Meerwein

Thermal and oxidative stability of the Ocimum basilicum L. essential oil/β-cyclodextrin supramolecular system

• Daniel I. Hădărugă,
• Nicoleta G. Hădărugă,
• Corina I. Costescu,
• Ioan David and
• Alexandra T. Gruia

Beilstein J. Org. Chem. 2014, 10, 2809–2820, doi:10.3762/bjoc.10.298

• -pinene), oxygenated monoterpenes (eucalyptol, linalool, α-terpineol, borneol and its acetate), phenolic derivatives (eugenol, methylchavicol (estragole)), sesquiterpene hydrocarbons (β-cubebene, β-caryophyllene, germacrene, etc.), and oxygenated sesquiterpenes (cadinol, spathulenol) [9][16][20][25