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

Adhesion, forces and the stability of interfaces

• Robin Guttmann,
• Johannes Hoja,
• Christoph Lechner,
• Reinhard J. Maurer and
• Alexander F. Sax

Beilstein J. Org. Chem. 2019, 15, 106–129, doi:10.3762/bjoc.15.12

Degenerative xanthate transfer to olefins under visible-light photocatalysis

• Atsushi Kaga,
• Xiangyang Wu,
• Joel Yi Jie Lim,
• Hirohito Hayashi,
• Yunpeng Lu,
• Edwin K. L. Yeow and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2018, 14, 3047–3058, doi:10.3762/bjoc.14.283

• functionalized cyclopentane 3an and pyrrolidine 3ao, respectively, via 5-exo-trig radical cyclization (Table 2, entries 13 and 14). The present method was capable in functionalizing olefins 2p and 2q installed on steroid scaffolds with high efficiency (Table 2, entries 15 and 16). We next examined the reactions

Olefin metathesis catalysts embedded in β-barrel proteins: creating artificial metalloproteins for olefin metathesis

• Daniel F. Sauer,
• Johannes Schiffels,
• Takashi Hayashi,
• Ulrich Schwaneberg and
• Jun Okuda

Beilstein J. Org. Chem. 2018, 14, 2861–2871, doi:10.3762/bjoc.14.265

• nm indicated the presence of the GH-type catalyst. Finally, the peak for the biohybrid conjugate was observed in ESI–TOF–MS suggesting successful covalent anchoring. Beside ring-closing metathesis (RCM) of 2,2-diallylpropane-1,3-diol to yield the corresponding cyclopentane derivative, the synthesized

Non-native autoinducer analogs capable of modulating the SdiA quorum sensing receptor in Salmonella enterica serovar Typhimurium

• Matthew J. Styles and
• Helen E. Blackwell

Beilstein J. Org. Chem. 2018, 14, 2651–2664, doi:10.3762/bjoc.14.243

• head group to a phenyl or cyclohexane was not well tolerated; however, cyclopentane, thiolactones, and the alternative stereochemistry, D-lactone were generally tolerated. Interestingly, 1-octanoyl-rac-glycerol (23) showed no agonism in this reporter assay, suggesting it does not act as an AHL signal

Synthesis of cis-hydrindan-2,4-diones bearing an all-carbon quaternary center by a Danheiser annulation

• Gisela V. Saborit,
• Carlos Cativiela,
• Ana I. Jiménez,
• Josep Bonjoch and
• Ben Bradshaw

Beilstein J. Org. Chem. 2018, 14, 2597–2601, doi:10.3762/bjoc.14.237

• through ring-expanding cyclopentane annulations based on a Prins–pinacol rearrangement [17][18] and Au(I)-catalyzed pinacol-terminated 1,6-enyne cyclizations [19][20], the C3a–C7a bond formation occurring in the last step of both procedures. Finally, Snyder gained access to the type A hydrindane nucleus

Novel photochemical reactions of carbocyclic diazodiketones without elimination of nitrogen – a suitable way to N-hydrazonation of C–H-bonds

• Liudmila L. Rodina,
• Xenia V. Azarova,
• Jury J. Medvedev,
• Dmitrij V. Semenok and
• Valerij A. Nikolaev

Beilstein J. Org. Chem. 2018, 14, 2250–2258, doi:10.3762/bjoc.14.200

• workup procedure hydrazone 2a and unreacted diazoketone 1a were isolated. 2-(2-(Tetrahydrofuran-2-yl)hydrazono)cyclopentane-1,3-dione (2a). Yield 168 mg (42%, calculated on the reacted diazodiketone 1a), bright-yellow oil; 1H NMR (400 MHz, CDCl3, δ) 12.93 (s, 1H), 5.61–5.53 (m, 1H), 4.08–3.99 (m, 1H

Studies towards the synthesis of hyperireflexolide A

• G. Hari Mangeswara Rao

Beilstein J. Org. Chem. 2018, 14, 2106–2111, doi:10.3762/bjoc.14.185

• cyclopentane 5, a functionalized key intermediate, is presented. Compound 5 is involved in hydrolysis, α-allylation at C-8 and α-methylation at C-10 stereoselectively from the convex face. Then it is subjected to cross metathesis to give α,β-unsaturated ketone 11 as precursor in the total synthesis of

• antifungal [2] and cytotoxic activities [3]. γ-Lactone-fused cyclopentanes are of vital importance in organic synthesis and are the most abundant substructures found in various naturally occurring molecules [4][5]. A cis-cyclopentane ring-fused γ-lactone is the key structural unit of many complex and

• challenging biologically active natural products [6][7][8][9][10][11][12][13][14][15][16][17][18][19]. The γ-lactone-fused cyclopentane ring system is also an important component for the synthesis of a variety of cyclopentanoid natural and unnatural products [20][21][22][23][24]. In the literature, numerous

Recent advances in synthetic approaches for medicinal chemistry of C-nucleosides

• Kartik Temburnikar and
• Katherine L. Seley-Radtke

Beilstein J. Org. Chem. 2018, 14, 772–785, doi:10.3762/bjoc.14.65

• give the desired cyclopentane ring (23) [73]. The biological data of these compounds has yet to be reported. Wang et al. synthesized a series of pyridine and pyrimidine C-nucleosides (24–26) that mimic the riboside of favipiravir in their effort to develop novel anti-influenza compounds (Figure 10A

• separable mixture of diastereomers (2:1). In addition, optically pure cyclopentanone (−)-45 was obtained by converting the cyclopentane 43 to camphanates (51, Figure 13B) followed by separation of the diastereomers [53]. Subsequent synthesis of the enol triflate (−)-46 (Figure 13B), Suzuki coupling and

Reagent-controlled regiodivergent intermolecular cyclization of 2-aminobenzothiazoles with β-ketoesters and β-ketoamides

• Irwan Iskandar Roslan,
• Kian-Hong Ng,
• Gaik-Khuan Chuah and
• Stephan Jaenicke

Beilstein J. Org. Chem. 2017, 13, 2739–2750, doi:10.3762/bjoc.13.270

• cyclic β-oxo esters ranging from cyclopentane to cyclooctane (Scheme 3, 5t–w). Interestingly, the ethers 5x and 5y were obtained when ethyl 4-chloroacetoacetate was reacted with 2-amino-6-methylbenzothiazole in a mixed solvent system of toluene with 2-butanol or isopentanol, respectively. The Cl is

Fluorination of some highly functionalized cycloalkanes: chemoselectivity and substrate dependence

• Attila Márió Remete,
• Melinda Nonn,
• Santos Fustero,
• Matti Haukka,
• Ferenc Fülöp and
• Loránd Kiss

Beilstein J. Org. Chem. 2017, 13, 2364–2371, doi:10.3762/bjoc.13.233

• amino acids and their analogous derivatives have gained considerable interest in pharmaceutical chemistry as bioactive compounds. Some derivatives (e.g., peramivir, oseltamivir or laninamivir) are known as antiviral drugs [19][20][21][22], while other cyclopentane β-amino acids (e.g., icofungipen

• dihydroxylated cyclic β-amino acid esters. Our study started with the fluorination of racemic dihydroxylated cyclopentane cis- or trans-β-amino acid esters (±)-1 and (±)-4 [23][24][25][26]. The preliminary investigations were performed with the commercially available fluorinating agents mentioned above in

• cyclopentane β-amino ester (±)-6 with Deoxofluor under various conditions provided an unidentifiable mixture of products. However, the reaction of diol (±)-6 with 1.5 equiv of Deoxofluor in the presence of DBU as the base furnished aziridine derivative (±)-7 within 10 min through intramolecular cyclization via

Aggregation behaviour of a single-chain, phenylene-modified bolalipid and its miscibility with classical phospholipids

• Simon Drescher,
• Vasil M. Garamus,
• Christopher J. Garvey,
• Annette Meister and
• Alfred Blume

Beilstein J. Org. Chem. 2017, 13, 995–1007, doi:10.3762/bjoc.13.99

• in the chemical structure of those archaeal membrane lipids: the alkyl chains are connected via ether linkages in the inverse sn-2,3 configuration to the glycerol, the alkyl chains sometimes contain a varying number of cyclopentane rings or several methyl branches [2][3], and some of the archaeal

Organofluorine chemistry: Difluoromethylene motifs spaced 1,3 to each other imparts facial polarity to a cyclohexane ring

• Mathew J. Jones,
• Ricardo Callejo,
• Alexandra M. Z. Slawin,
• Michael Bühl and
• David O'Hagan

Beilstein J. Org. Chem. 2016, 12, 2823–2827, doi:10.3762/bjoc.12.281

• attractive for drug discovery research and new materials [18]. In our own lab we have been exploring the synthesis and properties of differently fluorinated aliphatic structures based on the cyclopentane (1) and cyclohexane (2 and 3) rings, compounds which can show quite large dipole moments depending on the

A new and expeditious synthesis of all enantiomerically pure stereoisomers of rosaprostol, an antiulcer drug

• Wiesława Perlikowska,
• Remigiusz Żurawiński and
• Marian Mikołajczyk

Beilstein J. Org. Chem. 2016, 12, 2234–2239, doi:10.3762/bjoc.12.215

• C-2 of the cyclopentane ring opposite to that in natural prostaglandins of the A and J series. Therefore these compounds are expected to exhibit an increased biological stability as compared with 1a and 1b, and to be more efficacious in the treatment of gastric ulcers [23]. Recently we devised and

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

• for the oxidative production of valuable intermediates [264][265][266][267][268][269]. The asymmetric oxidation of 3-substituted cyclopentane-1,2-diones 87a–f is an efficient tool in organic synthesis for the preparation of unsymmetrical γ-lactone acids 88a–f with high optical purity and good yields

• (Table 6). These γ-lactone acids are valuable substrates for the synthesis of compounds with potentially useful pharmacological properties, such as homocitrates, alkyl- and aryl-substituted nucleosides [270][271][272]. The reaction starts with an asymmetric epoxidation of the substituted cyclopentane-1,2

Synergistic chiral iminium and palladium catalysis: Highly regio- and enantioselective [3 + 2] annulation reaction of 2-vinylcyclopropanes with enals

• Haipan Zhu,
• Peile Du,
• Jianjun Li,
• Ziyang Liao,
• Guohua Liu,
• Hao Li and
• Wei Wang

Beilstein J. Org. Chem. 2016, 12, 1340–1347, doi:10.3762/bjoc.12.127

• catalytic regio- and enantioselective [3 + 2] annulation process, which offers a new approach to synthetically important heavily functionalized chiral cyclopentane structures 3, bearing at least 3 stereogenic centers in this one-pot operation [77][78]. To test the feasibility of the designed [3 + 2

• , entry 8). It was found that the reaction took place to afford the desired cyclopentane 3a. Encouraged by this result, we carried out further investigations of the co-catalysts promoted process (Table 2). First, we determined the diastereo- and enantioselectivity of the reaction. The 1H NMR of the

Unusual traits of cis and trans-2,3-dibromo-1,1-dimethylindane on the way from 1,1-dimethylindene to 2-bromo-, 3-bromo-, and 2,3-dibromo-1,1-dimethylindene

• Rudolf Knorr,
• David S. Stephenson,
• Ernst Lattke,
• Petra Böhrer and
• Jakob Ruhdorfer

Beilstein J. Org. Chem. 2016, 12, 1178–1184, doi:10.3762/bjoc.12.113

• (no cyclopentane, no benzene), a voluminous precipitate began to emerge slowly at rt within ca. one hour. When this colorless powder of 2-bromo-3-lithio-1,1-dimethylindene (10) had settled after 20 hours at rt, the supernatant was withdrawn by syringe, and the residue was washed with dry pentane (3

Enantioselective carbenoid insertion into C(sp³)–H bonds

• J. V. Santiago and
• A. H. L. Machado

Beilstein J. Org. Chem. 2016, 12, 882–902, doi:10.3762/bjoc.12.87

• reagents, also used as solvent, were cyclopentane, cyclohexane and cycloheptane. Two factors are noteworthy in this work. Unlike the carboxamide complexes (R)-18 and (S)-18 previously reported by Doyle and coworkers (Table 2), where the complexation of the chiral ligand to rhodium atoms occurs through the

Study on the synthesis of the cyclopenta[f]indole core of raputindole A

• Nils Marsch,
• Mario Kock and
• Thomas Lindel

Beilstein J. Org. Chem. 2016, 12, 334–342, doi:10.3762/bjoc.12.36

• quaternary center was to be formed. Ideally, anellation of a cyclopentane would be possible at an indole with an intact enamine partial structure (B, Scheme 1). Such an approach seemed possible, because we had already cyclized 6-prenoylindole to a mixture of cyclopenta[f]- and -[g]indoles in a Nazarov-type

• assemble the cyclopenta[f]indole section present in the natural product raputindole A (1). As long as the cyclopentane ring would not be installed, it was indeed possible to work with 2,3-unsubstituted, N-Boc-protected indoles. In particular, the Mo/Au-catalyzed Meyer–Schuster rearrangement of

• the use of indolines instead of sensitive indoles. Cyclopentane anellation by SnCl4-induced cyclization of phenylvinylcarbinols became possible, at least for the sterically congested β-cyclocitral adduct 40 of N-TIPS-indoline. The less sterically demanding substrate 44 gave lower yields. Experiments

Cascade alkylarylation of substituted N-allylbenzamides for the construction of dihydroisoquinolin-1(2H)-ones and isoquinoline-1,3(2H,4H)-diones

• Ping Qian,
• Bingnan Du,
• Wei Jiao,
• Haibo Mei,
• Jianlin Han and
• Yi Pan

Beilstein J. Org. Chem. 2016, 12, 301–308, doi:10.3762/bjoc.12.32

• cycloalkanes 2 and N-methyl-N-(2-methylallyl)benzamide (4a). As indicated in Scheme 3, several cycloalkanes were well-tolerated in this radical reaction resulting in the corresponding product. In the case of cyclopentane (2b), a slightly lower chemical yield was obtained (46%, 5ab), while the reactions of

SmI₂-mediated dimerization of indolylbutenones and synthesis of the myxobacterial natural product indiacen B

• Nils Marsch,
• Peter G. Jones and
• Thomas Lindel

Beilstein J. Org. Chem. 2015, 11, 1700–1706, doi:10.3762/bjoc.11.184

• and Meyer–Schuster rearrangement 6-prenoylindole was synthesized and reductively dimerized to a cyclopentane in a [3 + 2] cycloaddition by treatment with SmI2 in THF. From 4-iodoindole, the natural product indiacen B from the myxobacterium Sandaracinus amylolyticus was synthesized for the first time

• be too distant from each other to show an nOe. In any cyclopentane conformation this would be the case for hydrogen atoms located in 1,3-trans-position. Thus, the presence of a NOESY cross peak would exclude 1,3-trans-orientation of the respective hydrogens. In diastereomers 6, 7, and 8 there were

• , exclusive trans-arrangement of aryl substituents at the cyclopentane ring had been observed [21][22][23][24]. Aryl substituents generally prefer the antiperiplanar arrangement, as observed by Zhou and Zhang, who reductively dimerized chalcone derivatives to trans-diarylated cyclopentanols [23]. Cis isomers