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

• to cyclopentane skeleton, as well as its stereochemistry, was originally elucidated as 1' as shown in Figure 1, on the basis of detailed analysis of 1D and 2D NMR spectroscopy. Spiroviolene was also found to be produced by several bacterial strains harboring SvS homologs [6][7], as well as putative

Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles

• Péter Kisszékelyi and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44

• . presented their work on the asymmetric desymmetrization of cyclopentene-1,3-diones 5 (Scheme 3) [23]. Following the Cu(OTf)2-catalyzed conjugate addition of R2Zn, the enolate 6 was trapped by several aromatic aldehydes 7. These complex chiral cyclopentane derivatives 8 bearing all-carbon quaternary

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

• cyclooctane ring fused to a cyclopentane ring, i.e., a [5-8] bicyclic ring system. This review focuses on the different strategies elaborated to construct this [5-8] bicyclic ring system and their application in the total synthesis of terpenes over the last two decades. The overall approaches involve the

• construction of the 8-membered ring from an appropriate cyclopentane precursor. The proposed strategies include metathesis, Nozaki–Hiyama–Kishi (NHK) cyclization, Pd-mediated cyclization, radical cyclization, Pauson–Khand reaction, Lewis acid-promoted cyclization, rearrangement, cycloaddition and biocatalysis

• sesquiterpenes (C15), share a common bicyclo[3.6.0]undecane core which is characterized by the presence of a cyclooctane ring fused to a cyclopentane ring i.e., a [5-8] bicyclic ring system (Figure 1). In most cases, additional rings are present and original strategies have been considered to construct this

1,4-Dithianes: attractive C2-building blocks for the synthesis of complex molecular architectures

• Bram Ryckaert,
• Ellen Demeyere,
• Frederick Degroote,
• Hilde Janssens and
• Johan M. Winne

Beilstein J. Org. Chem. 2023, 19, 115–132, doi:10.3762/bjoc.19.12

• quaternary centers is tackled by the direct cycloaddition of allyl cation 90 across a tetrasubstituted olefin 95, at the same time elaborating the cyclopentane core of this natural product. The completion of this short synthesis also nicely showcases the use of dihydrodithiinmethanol 90 as a synthetic

Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• 90. Total syntheses of magninoids and guignardones (Lou 2021) [47]: Magninoids and guignardones are two classes of biogenetically related meroterpenoids, bearing a highly substituted cyclopentane moiety and a 6-oxabicyclo[3.2.1]octane fragment [48][49]. These classes exhibit diverse biological

Total synthesis of grayanane natural products

• Nicolas Fay,
• Rémi Blieck,
• Cyrille Kouklovsky and
• Aurélien de la Torre

Beilstein J. Org. Chem. 2022, 18, 1707–1719, doi:10.3762/bjoc.18.181

• -membered ring closure through a SmI2-promoted pinacol coupling. This reaction had been previously described by the same group and proved to be highly effective [23]. For rings A, C and D, other SmI2-promoted steps were employed, giving respectively the cyclopentane A ring moiety and the bicyclo[3.2.1

Radical cation Diels–Alder reactions of arylidene cycloalkanes

• Kaii Nakayama,
• Hidehiro Kamiya and
• Yohei Okada

Beilstein J. Org. Chem. 2022, 18, 1100–1106, doi:10.3762/bjoc.18.112

• compound 9 was obtained in good yield. The arylidene cyclopentane 6 and cyclohexane 7 were found to be less effective for the reaction and in particular, the former (6) was almost totally unsuccessful. Although the mechanism remains unclear, Knowles and Romanov-Michailidis recently reported that a similar

Copper-catalyzed multicomponent reactions for the efficient synthesis of diverse spirotetrahydrocarbazoles

• Shao-Cong Zhan,
• Ren-Jie Fang,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2022, 18, 796–808, doi:10.3762/bjoc.18.80

• common cyclic 1,3-diones could be applied in this catalytic system. To our delight, when cyclopentane-1,3-dione was used to replace 1,3-dimethylbarbituiric acid under the same conditions, the desired product 5a was obtained in 74% yield with excellent diastereoselectivity (dr > 20:1). Furthermore, we

• 110 °C for about three hours. After removing the solvent by evaporating at reduced pressure, the residue was subjected to column chromatography with ethyl acetate and light petroleum (v/v = 1:5–1:8) as eluent to give pure 5a–k. 2,4-Diphenyl-1,2,4,9-tetrahydrospiro[carbazole-3,1'-cyclopentane]-2',5

Tosylhydrazine-promoted self-conjugate reduction–Michael/aldol reaction of 3-phenacylideneoxindoles towards dispirocyclopentanebisoxindole derivatives

• Sayan Pramanik and
• Chhanda Mukhopadhyay

Beilstein J. Org. Chem. 2022, 18, 469–478, doi:10.3762/bjoc.18.49

• . Again, in 2018, Yang et al. [26] synthesized functionalized dispiro[indoline-3,1-cyclopentane-3,3-indolines] via cyclodimerization of 3-phenacylideneoxindolines with benzoyl hydrazides and arylhydrazines. Encouraged by these synthetic methodologies and in continuation to our efforts towards the

• -ylidene)acetate, but unlike 3-phenacylideneoxindole this substrate does not take part in the reductive cyclization. In the prepared dispirocyclopentylbisoxindoles, there are four diastereomeric centers in the newly formed cyclopentane ring, so there is a possibility for existence of many diastereomers for

Asymmetric organocatalytic Michael addition of cyclopentane-1,2-dione to alkylidene oxindole

• Estelle Silm,
• Ivar Järving and
• Tõnis Kanger

Beilstein J. Org. Chem. 2022, 18, 167–173, doi:10.3762/bjoc.18.18

• Estelle Silm Ivar Jarving Tonis Kanger Department of Chemistry and Biotechnology, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia 10.3762/bjoc.18.18 Abstract An asymmetric Michael reaction between cyclopentane-1,2-dione and alkylidene oxindole was studied in the

• presence of a multifunctional squaramide catalyst. Michael adducts were obtained in high enantioselectivities and in moderate diastereoselectivities. Keywords: cyclopentane-1,2-dione; enantioselective catalysis; Michael addition; organocatalysis; squaramide; Introduction Diketones are generally very

• in carbohydrate chemistry [15]. Cyclic six-membered 1,2-diketones have been shown to react with benzylidene malononitriles [7][16], β-nitrostyrenes [17] and substituted propionaldehydes [18]. For a while, there were no examples related to cyclopentane-1,2-dione (CPD). In 2004, the first instance of

A study on selective transformation of norbornadiene into fluorinated cyclopentane-fused isoxazolines

• Zsanett Benke,
• Attila M. Remete and
• Loránd Kiss

Beilstein J. Org. Chem. 2021, 17, 2051–2066, doi:10.3762/bjoc.17.132

• oxide 1,3-dipolar cycloaddition/ROM/CM strategies was presented. The stepwise functionalization of norbornadiene across the ring olefin bonds generated fluorine-containing alkenylated cyclopentane-fused isoxazolines. The synthetic protocol was based on selective nitrile oxide cycloaddition to the

• norbornadiene C=C bond, followed by ROM of the resulting cyclopentane-fused isoxazolines. In the final step, selective CM by chemodifferentiation of the newly created olefin bonds on the resulting alkenylated derivatives took place. As coupling olefin partners in CM reactions, several commercial fluorine

• . Some commercial Ru-based catalysts used in the current work. Synthesis of divinylated cyclopentane-fused isoxazolines [41]. Various fluorine-containing olefins used in the current work. Chemoselective CM reaction due to steric hindrance. Cross-metathesis of divinylated isoxazoline (±)-4 with

Chemical approaches to discover the full potential of peptide nucleic acids in biomedical applications

• Nikita Brodyagin,
• Martins Katkevics,
• Venubabu Kotikam,
• Christopher A. Ryan and
• Eriks Rozners

Beilstein J. Org. Chem. 2021, 17, 1641–1688, doi:10.3762/bjoc.17.116

• co-workers found that restricting the backbone’s conformation with the fused S,S-cyclopentane ring increased the binding affinity of cpPNA (Figure 4) for complementary DNA and RNA compared to the unmodified PNA [55][56]. Govindaraju, Kumar and Ganesh [57][58] reported that isolated S,R- and R,S

• -cyclopentane modifications had variable effects on PNA binding affinity depending on their location (C-terminus, middle, or N-terminus) in PNA, while fully S,R- and R,S-modified cpPNAs were binding stronger to complementary DNA and RNA than the unmodified PNA. The R,S-modified cpPNAs appeared to be somewhat

• . Recently, more detailed biophysical and structural studies on S,S-cpPNA by Appella and co-workers [59][60] show that the S,S-configuration of cyclopentane modification enforces dihedral angles of PNA backbone favorable for binding to complementary DNA. PNA binding affinity and sequence selectivity increase

Synthesis of β-triazolylenones via metal-free desulfonylative alkylation of N-tosyl-1,2,3-triazoles

• Soumyaranjan Pati,
• Renata G. Almeida,
• Eufrânio N. da Silva Júnior and
• Irishi N. N. Namboothiri

Beilstein J. Org. Chem. 2021, 17, 762–770, doi:10.3762/bjoc.17.66

• addition (see mechanism, Scheme 4, vide infra). On the other hand, 4-tert-butyl analog 1d underwent the reaction smoothly to form the corresponding product 3d in 70% yield. However, due to the inconsistent results with cyclohexanedione 2a, further scope was investigated by employing cyclopentane-1,3-dione

• 2b. The model triazole 1a furnished the product 3e in 55% yield within 18 h. To our delight, triazoles 1b and 1c, bearing 4-tolyl and 4-methoxyphenyl groups, which did not react with 1,3-cyclohexanedione 2a reacted smoothly with cyclopentane-1,3-dione 2b to deliver the products 3f and 3g in 71% and

• ). This might also be attributed to the lower yields obtained in certain cases. It may be noted that the outcome of the reaction is highly dependent on the nature of the 1,3-dicarbonyl compound. In the case of cyclic-1,3-dicarbonyls, cyclopentane-1,3-dione 2b reacts smoothly in almost all cases whereas

α,γ-Dioxygenated amides via tandem Brook rearrangement/radical oxygenation reactions and their application to syntheses of γ-lactams

• Mikhail K. Klychnikov,
• Radek Pohl,
• Ivana Císařová and
• Ullrich Jahn

Beilstein J. Org. Chem. 2021, 17, 688–704, doi:10.3762/bjoc.17.58

• products, amides 9g,k with trisubstituted alkene units exclusively lead to isopropenylpyrrolidones 12g,k. A similar reactivity was observed before in thermal radical cyclizations leading to cyclopentane derivatives [74][75]. All γ-silyloxy amides 9a–k cyclize in the 5-exo mode via envelope transition

All-carbon [3 + 2] cycloaddition in natural product synthesis

• Zhuo Wang and
• Junyang Liu

Beilstein J. Org. Chem. 2020, 16, 3015–3031, doi:10.3762/bjoc.16.251

• -catalyzed intermolecular carboxylatve TMM [3 + 2] cycloaddition [36] of enone 65 and TMM donor 62 to forge the highly-substituted spirocyclic cyclopentane 66a [38] (Scheme 4A). Methylation of the resultant cyclopentane 66a gave methyl ester 66b in 93% yield over two steps. A six-step synthesis from ester

• are highlighted in lilac; cyclopentane structures forged by the all-carbon [3 + 2] cyclization are labeled in red). (A) The intermolecular all-carbon [3 + 2] cyclization features as the key reaction. (B) The intramolecular all-carbon [3 + 2] cycloaddition features as the key reaction. Representative

Synthesis of novel fluorinated building blocks via halofluorination and related reactions

• Attila Márió Remete,
• Tamás T. Novák,
• Melinda Nonn,
• Matti Haukka,
• Ferenc Fülöp and
• Loránd Kiss

Beilstein J. Org. Chem. 2020, 16, 2562–2575, doi:10.3762/bjoc.16.208

• , the mechanism is relatively straightforward. Instead of an E2 elimination, these compounds are deprotonated next to the ester group, which is closer to the CHBr unit. Then, the carbanion motif of the formed enolates (rac)-T8a and T8b afford the cyclopropane-fused cyclopentane dicarboxylate (rac)-27

• ends with (rac)-28, containing cis-annulated cyclopentane rings. Note, that the cyclopentane rings in (rac)-29 have a more strained trans-annulated attachment (Scheme 19). After finishing the study of the halofluorinations with NBS/Deoxo-Fluor® and NIS/Deoxo-Fluor® systems, our attention shifted to the

An overview on disulfide-catalyzed and -cocatalyzed photoreactions

• Yeersen Patehebieke

Beilstein J. Org. Chem. 2020, 16, 1418–1435, doi:10.3762/bjoc.16.118

• method is also applicable for the synthesis of a wide variety of cyclopentane derivatives [12]. In 2017, Huang and co-workers reported a [4 + 2] cycloaddition reaction promoted by blue LED light, using aromatic olefins as the precursor, an acridinium photoredox catalyst (Mes–Acr–Ph+BF4−), and disulfide

Recent advances in photocatalyzed reactions using well-defined copper(I) complexes

• Mingbing Zhong,
• Xavier Pannecoucke,
• Philippe Jubault and
• Thomas Poisson

Beilstein J. Org. Chem. 2020, 16, 451–481, doi:10.3762/bjoc.16.42

• aryl iodides and bromides into the corresponding aryl radical to use the latter in further transformations (Scheme 21). First, a 5-exo-trig cyclization was carried out to access indolines, dihydrobenzofurans, indanes, cyclopentane, and pyrrolidines. The cyclized products were isolated in good to

Copper-catalyzed enantioselective conjugate addition of organometallic reagents to challenging Michael acceptors

• Delphine Pichon,
• Jennifer Morvan,
• Christophe Crévisy and
• Marc Mauduit

Beilstein J. Org. Chem. 2020, 16, 212–232, doi:10.3762/bjoc.16.24

• /enolate trapping was also studied, providing the trans-cyclopentane product 56 as a single diastereoisomer (92% ee). In 2018, the same authors reported the 1,6- and 1,4-additions of various Grignard reagents to a wide scope of conjugated dienyl amides (Scheme 22) [51]. Interestingly, the authors observed

Current understanding and biotechnological application of the bacterial diterpene synthase CotB2

• Ronja Driller,
• Daniel Garbe,
• Norbert Mehlmer,
• Monika Fuchs,
• Keren Raz,
• Dan Thomas Major,
• Thomas Brück and
• Bernhard Loll

Beilstein J. Org. Chem. 2019, 15, 2355–2368, doi:10.3762/bjoc.15.228

• hydrolysis of the fatty acid ester bonds of lysophospholipids [31][41]. Moreover, cyclooctatin (5) was shown to be effective against Plasmodium falciparum with an IC50 of 7.14 µg/mL along with very low cytotoxicity [42]. CotB2 belongs to the class of cyclopentane-forming diterpene synthases [46], a class of

Synthesis of 1-azaspiro[4.4]nonan-1-oxyls via intramolecular 1,3-dipolar cycloaddition

• Yulia V. Khoroshunova,
• Denis A. Morozov,
• Andrey I. Taratayko,
• Polina D. Gladkikh,
• Yuri I. Glazachev and
• Igor A. Kirilyuk

Beilstein J. Org. Chem. 2019, 15, 2036–2042, doi:10.3762/bjoc.15.200

• studied and compared to those of previously published (1S,2R,3′S,4′S,5′S,2″R)-dispiro[(2-hydroxymethyl)cyclopentan-1,2′-(3′,4′-di-tert-butoxy)pyrrolidine-5′,1″-(2″-hydroxymethyl)cyclopentane]-1′-oxyl (1). Keywords: aldonitrone; 1,3-dipolar cycloaddition; pyrrolidine nitroxides; 1-pyrroline-N-oxide

• effect may be useful for structural studies by means of PELDOR or DQC [5]. We recently reported the synthesis of sterically shielded pyrrolidine nitroxide 1 via a stereospecific consecutive assembly of two spiro-(2-hydroxymethyl)cyclopentane moieties. These procedures included the addition of pent-4

• with only one spiro(2-hydroxymethyl)cyclopentane moiety. The rates of reduction of the new nitroxides with ascorbate were measured. Results and Discussion Aldonitrones 5b,c were prepared similarly to the well-known synthesis of 5,5-dimethyl-1-pyrroline-1-oxide (DMPO, 5a) [9][10] from nitrocyclohexane

Enantioselective PCCP Brønsted acid-catalyzed aza-Piancatelli rearrangement

• Gabrielle R. Hammersley,
• Meghan F. Nichol,
• Helena C. Steffens,
• Jose M. Delgado,
• Gesine K. Veits and
• Javier Read de Alaniz

Beilstein J. Org. Chem. 2019, 15, 1569–1574, doi:10.3762/bjoc.15.160

• acid; cyclopentane; furylcarbinols; PCCP; Introduction The discovery of a wide range of cyclopentane containing natural products [1][2] and biologically active molecules such as palau’amine [3][4], agelastatin A [5][6][7], pactamycin [8][9][10], and aristeromycin [11][12], has created a demand for new

Transient and intermediate carbocations in ruthenium tetroxide oxidation of saturated rings

• Manuel Pedrón,
• Laura Legnani,
• Maria-Assunta Chiacchio,
• Pierluigi Caramella,
• Tomás Tejero and
• Pedro Merino

Beilstein J. Org. Chem. 2019, 15, 1552–1562, doi:10.3762/bjoc.15.158

• tetroxide-mediated oxidation of cyclopentane, tetrahydrofuran, tetrahydrothiophene and N-substituted pyrrolidines has been studied computationally by DFT and topological (analysis of the electron localization function, ELF) methods. In agreement with experimental observations and previous DFT calculations

• oxidation of cyclopentane, tetrahydrofuran, tetrahydrothiophene, and N-methyl- and N-benzylpyrrolidine to evaluate the extension in which transient carbocations can be formed (and whether they can become energy minima) during the rate-limiting step (Scheme 3). The RuO4 oxidation of cyclopentane [44] and

• calculations are those indicated in Scheme 3. Results and Discussion We first studied the oxidations of cyclopentane (R1), tetrahydrofuran (R2) and tetrahydrothiophene (R3, Scheme 4). The geometries of all stationary points were optimized at the B3LYP-d3bj/Def2SVP level of theory in the gas phase and

Synthesis of polydicyclopentadiene using the Cp₂TiCl₂/Et₂AlCl catalytic system and thin-layer oxidation of the polymer in air

• Zhargolma B. Bazarova,
• Ludmila S. Soroka,
• Alex A. Lyapkov,
• Мekhman S. Yusubov and
• Francis Verpoort

Beilstein J. Org. Chem. 2019, 15, 733–745, doi:10.3762/bjoc.15.69

• region contains a wide signal corresponding to the superposition of resonances of –СН and –СН2 groups of cyclopentene and cyclopentane rings. The region from 5.0 to 6.3 ppm contains several wide signals corresponding to resonances of protons of double bonds of the polymer chain and the cyclopentene ring

New sesquiterpenoids from the South China Sea soft corals Clavularia viridis and Lemnalia flava

• Qihao Wu,
• Yuan Gao,
• Meng-Meng Zhang,
• Li Sheng,
• Jia Li,
• Xu-Wen Li,
• Hong Wang and
• Yue-Wei Guo

Beilstein J. Org. Chem. 2019, 15, 695–702, doi:10.3762/bjoc.15.64

• of the chiral centers on the cyclopentane ring were determined to be the same as 1 by inspection of the proton coupling constants (Table 1) and NOESY experiments (Figure 3). Thus, compound 2 was determined to be the debrominated derivative of 1, namely, clalaurenol A. Compound 3 was observed as an