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

• Terpene compounds probably represent the most diversified class of secondary metabolites. Some classes of terpenes, mainly diterpenes (C20) and sesterterpenes (C25) and to a lesser extent sesquiterpenes (C15), share a common bicyclo[3.6.0]undecane core which is characterized by the presence of a

• [2]. In several cases, terpenes possess a complex polycyclic framework which challenged the chemistry community over the years to develop efficient approaches and methodologies to access them. Indeed, some classes of terpenes, mainly diterpenes (C20) and sesterterpenes (C25) and to a lesser extent

• ketyl addition, one would have to wait almost two decades before employing it again in eight-membered ring closure. Among the diterpenes and sesterterpenes featuring a cyclooctane framework, (+)-pleuromutilin (1) was recently targeted by Reisman’s group through an elegant approach involving a SmI2

Anti-inflammatory aromadendrane- and cadinane-type sesquiterpenoids from the South China Sea sponge Acanthella cavernosa

• Shou-Mao Shen,
• Qing Yang,
• Yi Zang,
• Jia Li,
• Xueting Liu and
• Yue-Wei Guo

Beilstein J. Org. Chem. 2022, 18, 916–925, doi:10.3762/bjoc.18.91

• . Several examples of enantiomers formation catalyzed by different terpene synthases were also reported. Jiang et al. characterized two new fungal bifunctional terpene synthases, FoFS and AtAS (identity 27.8%), that catalyzed the formation of a pair of enantiomeric sesterterpenes [23]. Two groups

Targeting active site residues and structural anchoring positions in terpene synthases

• Anwei Hou and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2021, 17, 2441–2449, doi:10.3762/bjoc.17.161

• otherwise conserved Asp in this position. The relative proportions of the sesterterpenes were slightly shifted in favour of the main product 1 and compound 5, while the production of 2 and 3 was decreased. Interestingly, the restoration of the pyrophosphate sensor in the G180R variant resulted in a

• relative total production of A222V (129 ± 8%) was determined in comparison to the total production of sesterterpenes by the wildtype (= 100%, Figure 6 and Supporting Information File 1, Table S3). To further investigate the influence of bulky residues in this position, expression vectors for the SmTS1

On the mass spectrometric fragmentations of the bacterial sesterterpenes sestermobaraenes A–C

• Anwei Hou and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2020, 16, 2807–2819, doi:10.3762/bjoc.16.231

• investigation of the electron impact mass spectrometry (EIMS) fragmentation reactions of these sesterterpene hydrocarbons. Keywords: isotopes; mass spectrometry; reaction mechanisms; sesterterpenes; Streptomyces mobaraensis; Introduction The sestermobaraenes A–F (1–6) and sestermobaraol (7) are a series of

• bacterial sesterterpenes that were recently discovered by us from the actinomycete Streptomyces mobaraensis through a genome mining approach (Figure 1) [1]. All seven compounds are produced by a canonical terpene synthase, representing the first reported sesterterpene synthase of the classical type I from

• individual carbon position by enzymatic synthesis [14][29][30][31][32]. Here we report on the MS fragmentation mechanisms for the bacterial compounds sestermobaraenes A, B, and C, representing the first mechanistic study of this kind for sesterterpenes. Results and Discussion Experimental basis The 25

Antibacterial scalarane from Doriprismatica stellata nudibranchs (Gastropoda, Nudibranchia), egg ribbons, and their dietary sponge Spongia cf. agaricina (Demospongiae, Dictyoceratida)

• Cora Hertzer,
• Stefan Kehraus,
• Nils Böhringer,
• Fontje Kaligis,
• Robert Bara,
• Dirk Erpenbeck,
• Gert Wörheide,
• Till F. Schäberle,
• Heike Wägele and
• Gabriele M. König

Beilstein J. Org. Chem. 2020, 16, 1596–1605, doi:10.3762/bjoc.16.132

• Carteriospongia (Thorectidae), as well as Hyattella and Spongia (Spongiidae). A geographical variation was described between D. atromarginata populations from Sri Lanka and Australia, containing furanoditerpenes, and a D. atromarginata population from India, containing scalarane sesterterpenes as a consequence of

• of this compound. In general, scalarane sesterterpenes are bioactive metabolites, mainly isolated from marine sources, such as Dictyoceratida sponges and the nudibranchs that feed on them [7][25][29][33][56]. So far, only six scalaranes containing cyclopropane rings, constructed of C-4, C-19 and C-20

• from the previously reported scalaranes [25][29][33][42][56][61][62], the new metabolite is functionalized at C-11 instead of C-12 and has a cyclopropane ring bridging C-3, C-22 and C-4 of ring A. Scalarane sesterterpenes are considered as chemotaxonomic markers for the sponge families Thorectidae

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

• [116]. In some cases, bacterial TCs are able to accept oligoprenyl diphosphates with different lengths. Spata-13,17-diene (39) synthase is an extreme example that can convert FPP (9), GGPP (10), and geranylfarnesyl diphosphate (GFPP, 11) into sesquiterpenes, diterpenes, and sesterterpenes, respectively

Bipolenins K–N: New sesquiterpenoids from the fungal plant pathogen Bipolaris sorokiniana

• Chin-Soon Phan,
• Hang Li,
• Simon Kessler,
• Peter S. Solomon,
• Andrew M. Piggott and
• Yit-Heng Chooi

Beilstein J. Org. Chem. 2019, 15, 2020–2028, doi:10.3762/bjoc.15.198

• array of secondary metabolites, including sesquiterpenes [1][2][3][4][5][6][7], sesquiterpene-xanthones [8], diterpenes [9], sesterterpenes [10], cochlioquinones and peptides [11]. Moreover, several of these secondary metabolites are known to play important roles in mediating the virulence of these

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

• previously established the importance of conformation in the carbocation cyclization cascade [1], focusing on two sesterterpenes, i.e., quiannulatene [1][2] and sesterfisherol [3][4][5], as representative examples. These two sesterterpenes are synthesized via a 5/12/5 tricyclic intermediate, which leads to a

• conformational preorganization [20] of GFPP bound to a sesterterpene synthase on the reaction outcome, we computed the inherent atomic mobility in the carbocation intermediates during the biosynthesis of two sesterterpenes, quiannulatene and sesterfisherol. Two methyl groups, i.e., C20 and C23, remain static

• biosynthetic outcomes in other terpene-forming reactions. We are currently applying this approach to sesterterpenes that are synthesized through a 5/6/11 tricyclic intermediate. Experimental All calculations were carried out using GRRM11 [21][22][23][24][25] with Gaussian 09 [26]. All TS structures were

Domino ring-opening–ring-closing enyne metathesis vs enyne metathesis of norbornene derivatives with alkynyl side chains. Construction of condensed polycarbocycles

• Ritabrata Datta and
• Subrata Ghosh

Beilstein J. Org. Chem. 2018, 14, 2708–2714, doi:10.3762/bjoc.14.248

• derivatives with suitably located alkynyl side-chains as the key step. The structurally unique sesterterpenes retigeranic acid A (1a) and retigeranic acid B (1b, Figure 1) are representative examples of such complex polycyclic structures [44][45][46][47]. We speculated that domino ROM–RCEYM of the norbornene