Structure/affinity studies in the bicyclo-DNA series: Synthesis and properties of oligonucleotides containing bc^en-T and iso-tricyclo-T nucleosides

• Branislav Dugovic,
• Michael Wagner and
• Christian J. Leumann

Beilstein J. Org. Chem. 2014, 10, 1840–1847, doi:10.3762/bjoc.10.194

• in both nucleosides the furanose unit appears in an almost perfect 2’-endo conformation giving rise to a trans arrangement of torsion angle δ (O3’–C3’–C4’–C5’). In both structures the cyclopentane ring exists in a shallow envelope conformation with C5’ being slightly out of plane. This leads to a

• the conformation of the bicyclic ring system. A comparison of 8β and 11β with bc-T, having a saturated cyclopentane unit clearly reveals structural differences. The largest deviation is associated with the position of the 5’-OH group which is in a pseudoequatorial orientation in bc-T, giving rise to a

Stereoselective synthesis of carbocyclic analogues of the nucleoside Q precursor (PreQ₀)

• Sabin Llona-Minguez and
• Simon P. Mackay

Beilstein J. Org. Chem. 2014, 10, 1333–1338, doi:10.3762/bjoc.10.135

• -substituted analogues with interesting three-dimensional character, including chiral cyclopentane-1,2-diol and -1,2,3-triol derivatives. This unusual substitution pattern provides a useful starting point for the discovery of novel bioactive molecules. Keywords: diol synthesis; nucleoside; PreQ0

• -position of the heterocyclic core (systematic numbering) are scarce in the chemical literature and the methods available generally lack experimental information, making them unsatisfactory [18][19][20][21][22][23][24][25]. Inspired by the cyclopentane-1,2,3-triol motif present in noraristeromycin 5 (Figure

Cyclization–endoperoxidation cascade reactions of dienes mediated by a pyrylium photoredox catalyst

• Nathan J. Gesmundo and
• David A. Nicewicz

Beilstein J. Org. Chem. 2014, 10, 1272–1281, doi:10.3762/bjoc.10.128

• step is irrelevant, whereas the opposite scenario involving a benzylic radical intermediate would require a stereospecific addition of oxygen to the same face of the cyclopentane system as the isoprenyl cation in order for endoperoxide formation to occur. With optimized conditions identified, we sought

Synthesis of complex intermediates for the study of a dehydratase from borrelidin biosynthesis

• Frank Hahn,
• Nadine Kandziora,
• Steffen Friedrich and
• Peter F. Leadlay

Beilstein J. Org. Chem. 2014, 10, 634–640, doi:10.3762/bjoc.10.55

• , anticancer and anti-angiogenesis activities, which are probably caused by the inhibition of threonyl-tRNA synthetase and apoptosis induction by caspase activation [1][2][3][4]. It bears several unusual structural elements like a cyclopentane ring and a carbonitrile (Figure 1a), which are built-up by

Iron-catalyzed decarboxylative alkenylation of cycloalkanes with arylvinyl carboxylic acids via a radical process

• Jincan Zhao,
• Hong Fang,
• Jianlin Han and
• Yi Pan

Beilstein J. Org. Chem. 2013, 9, 1718–1723, doi:10.3762/bjoc.9.197

• the product 3p in 89% yield. In general, the stereoselectivity of this reaction was excellent and only trans-isomers were obtained in all cases. Next, other cycloalkanes, including cyclopentane, cycloheptane and cyclooctane, were reacted with different cinnamic acids 1, giving products 4a–f in 83–95

The preparation of several 1,2,3,4,5-functionalized cyclopentane derivatives

• André S. Kelch,
• Peter G. Jones,
• Ina Dix and
• Henning Hopf

Beilstein J. Org. Chem. 2013, 9, 1705–1712, doi:10.3762/bjoc.9.195

• with various bromination reagents. Whenever possible we confirm the structures of intermediate compounds or byproducts by X-ray structural analysis. Results and Discussion cis,cis,cis,cis-1,2,3,4,5-Pentakis(hydroxymethyl)cyclopentane (16) and derivatives The pentaalcohol 16 is a known compound, having

• the Supporting Information File 1. cis,cis,cis,trans-1,2,3,4,5- (26), cis,cis,trans,cis-1,2,3,4,5-Pentakis(methoxycarbonyl)cyclopentane (27) and several of their derivatives For the other two routes to precursors of [5]radialene (3) discussed here, the ten carbon atoms of the desired final product

• ; ellipsoids represent 30% probability levels. Structure of 32 in the crystal; ellipsoids represent 50% probability levels. The first members of the [n]radialene series and retrosynthesis for [5]radialene (3). Preparation of cis,cis,cis,cis-1,2,3,4,5-pentakis(hydroxymethyl)cyclopentane (16) according to

Substituent effect on the energy barrier for σ-bond formation from π-single-bonded species, singlet 2,2-dialkoxycyclopentane-1,3-diyls

• Jianhuai Ye,
• Yoshihisa Fujiwara and
• Manabu Abe

Beilstein J. Org. Chem. 2013, 9, 925–933, doi:10.3762/bjoc.9.106

• and cyclopentane-1,3-diyls. Experimental investigation of the chemistry of singlet diradicals has become possible. The present study explores the substituents and the effect of their substitution pattern at the C(1)–C(3) positions on the lifetime of singlet octahydropentalene-1,3-diyls to understand

• -diyls [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and cyclopentane-1,3-diyls [17][21][22][23][24][25][26]. Detailed experimental study of singlet diradical chemistry is thus now possible using the long-lived localized singlet diradicals. So far, we have studied singlet diradical

• , 702; UV (MTHF) λmax 365 (ε 106.7); 1H NMR (500 MHz, C6D6) δ 1.20–1.75 (m, 6H), 3.69 (t, J = 5.13 Hz, 2H), 4.15 (s, 2H), 4.29 (s, 2H), 6.90–8.19 (m, 20H, overlapping with C6H6); 13C NMR (125 MHz, C6D6) δ 25.96 (t, CH2, cyclopentane), 28.16 (t, CH2, cyclopentane), 49.27 (d, CH, cyclopentane), 66.16 (t

Some aspects of radical chemistry in the assembly of complex molecular architectures

• Béatrice Quiclet-Sire and
• Samir Z. Zard

Beilstein J. Org. Chem. 2013, 9, 557–576, doi:10.3762/bjoc.9.61

• addition to phenyl vinyl sulfone and closure to form the cyclopentane ring in 19, and then by a second intermolecular addition to phenyl vinyl sulfone to furnish radical 20, which finally evolves into the observed product 21 by transfer of the pyridylthiyl group from the starting Barton ester 16. Even

Synthesis of spiro[dihydropyridine-oxindoles] via three-component reaction of arylamine, isatin and cyclopentane-1,3-dione

• Yan Sun,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2013, 9, 8–14, doi:10.3762/bjoc.9.2

• -component reactions of arylamine, isatin and cyclopentane-1,3-dione in acetic acid at room temperature. On the other hand the condensation of isatin with two equivalents of cyclopentane-1,3-dione gave 3,3-bis(2-hydroxy-5-oxo-cyclopent-1-enyl)oxindole in high yields. The reaction mechanism and substrate

• three-component reaction of arylamine, isatin and cyclopentane-1,3-dione. Results and Discussion Recently we found that the four-component reactions of arylamine, acetylenedicarboxylate, isatin and dimedone in acetic acid resulted in the novel functionalized tetrahydrospiro[indoline-3,2’-quinoline

• -5-methylisatin and cyclopentane-1,3-dione in acetic acid was carried out at room temperature. After workup, we were a little surprised to find that there was no unit of acetylenedicarboxylate in the obtained product (Scheme 1b). In another experiment, the three-component reaction of isatin

Features of the behavior of 4-amino-5-carboxamido-1,2,3-triazole in multicomponent heterocyclizations with carbonyl compounds

• Eugene S. Gladkov,
• Katerina A. Gura,
• Svetlana M. Sirko,
• Sergey M. Desenko,
• Ulrich Groth and
• Valentin A. Chebanov

Beilstein J. Org. Chem. 2012, 8, 2100–2105, doi:10.3762/bjoc.8.236

• '-cyclopentane}-3-carboxamide (4a) or 5,6,7,8-tetrahydro-4H-spiro{[1,2,3]triazolo[5,1-b]quinazoline-9,1'-cyclohexane}-3-carboxamide (4b) under all the conditions tested. The best results were observed in the case of microwave-assisted synthesis in methanol at 120 °C. Spirocompound 4c may be obtained by a

Tricyclic flavonoids with 1,3-dithiolium substructure

• Lucian G. Bahrin,
• Peter G. Jones and
• Henning Hopf

Beilstein J. Org. Chem. 2012, 8, 1999–2003, doi:10.3762/bjoc.8.226

• led to the synthesis of derivative 1, a selective estrogen receptor β agonist (SERBA-1, Figure 1) [5]. Studies that focus on the structure–activity relationship were reported [6][7]. It was shown that a cyclopentane ring at the 3,4-carbon positions (labeled C, Figure 1) leads to a substantial rise in

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

Stereoselective synthesis of trans-fused iridoid lactones and their identification in the parasitoid wasp Alloxysta victrix, Part I: Dihydronepetalactones

• Nicole Zimmermann,
• Robert Hilgraf,
• Lutz Lehmann,
• Daniel Ibarra and
• Wittko Francke

Beilstein J. Org. Chem. 2012, 8, 1246–1255, doi:10.3762/bjoc.8.140

• ]. Similar results of highly stereoselective hydroborations of structurally related chiral cyclopentene derivatives have been reported [20][21]. Synthesis of trans,trans-dihydronepetalactone b To install a trans,trans-configuration between the substituents at C5-C1 and C1-C2 of the cyclopentane backbone

• synthesis of the cis,trans dihydronepetalactone c, a cis,trans-configuration between the substituents at C5-C1 and C1-C2 of the cyclopentane backbone needed to be established. With acetate 16 as the key intermediate, a stereoselective “syn”-addition of hydrogen from the same side as the (R)-configured side

Chiral multifunctional thiourea-phosphine catalyzed asymmetric [3 + 2] annulation of Morita–Baylis–Hillman carbonates with maleimides

• Hong-Ping Deng,
• De Wang,
• Yin Wei and
• Min Shi

Beilstein J. Org. Chem. 2012, 8, 1098–1104, doi:10.3762/bjoc.8.121

• ] annulation of MBH carbonates with maleimides, which can efficiently construct functionalized cyclopentenes bearing three contiguous stereocenters in moderate to excellent yields and excellent diastereo- and enantioselectivities, and the product can be efficiently transformed into a cyclopentane containing

Diarylethene-modified nucleotides for switching optical properties in DNA

• Sebastian Barrois and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2012, 8, 905–914, doi:10.3762/bjoc.8.103

• , forms the central cyclopentane ring of diarylethene 10. Subsequently, the ethynyl linker is attached to 10 by treatment with TMS-protected acetylene in a Pd-catalyzed cross-coupling reaction. Careful evaluation of this synthetic step revealed that the best yield (43%) of the mono-ethinylated product 11

Synthesis of axially chiral oxazoline–carbene ligands with an N-naphthyl framework and a study of their coordination with AuCl·SMe₂

• Feijun Wang,
• Shengke Li,
• Mingliang Qu,
• Mei-Xin Zhao,
• Lian-Jun Liu and
• Min Shi

Beilstein J. Org. Chem. 2012, 8, 726–731, doi:10.3762/bjoc.8.81

• papers of relevance. Tomioka and co-workers disclosed the first chiral NHC–Au(I) complex 1 (Figure 1), which was applied to catalyze the asymmetric cyclization of 1,6-enynes giving the corresponding cyclopentane derivatives with moderate enantioselectivity up to 59% [9][10]. Iglesias and co-workers

Synthesis of 2,6-disubstituted tetrahydroazulene derivatives

• Zakir Hussain,
• Henning Hopf,
• Khurshid Ayub and
• S. Holger Eichhorn

Beilstein J. Org. Chem. 2012, 8, 693–698, doi:10.3762/bjoc.8.77

• analysis of 8 revealed [22] an azulene framework that is partially hydrogenated to a cyclopentane subunit in places where molecules are slightly disordered in the lattice. These molecules represent the slightly torsionally distorted enantiomers of 8. At this stage we did not find any hydrogen atom at

Synthesis of highly functionalized β-aminocyclopentanecarboxylate stereoisomers by reductive ring opening reaction of isoxazolines

• Melinda Nonn,
• Loránd Kiss,
• Reijo Sillanpää and
• Ferenc Fülöp

Beilstein J. Org. Chem. 2012, 8, 100–106, doi:10.3762/bjoc.8.10

• carbamate side (cis to –NHBoc) of the cyclopentane skeleton. This was confirmed by X-ray analysis of 12. In order to increase the number of multifunctionalized amino ester stereoisomers, we next examined the reductions of isoxazoline-fused cispentacin and transpentacin stereoisomers (3–6) [49]. Reactions

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103

• example, the heteroaromatic thiophene-based imine gave the desired products 379 in good yield (70%), albeit in moderate enantioselectivity (58% ee). In the study of enantioselective cyclization, for example, of 1,6-enynes 381 for the synthesis of cyclopentane derivatives 382, Matsumoto and co-workers

Carbasugar analogues of galactofuranosides: α-O-linked derivatives

• Jens Frigell and
• Ian Cumpstey

Beilstein J. Org. Chem. 2010, 6, 1127–1131, doi:10.3762/bjoc.6.129

• -membered ring series, irrespective of the preferred envelope conformation of the epoxide, and that stereoelectronic effects are thus likely to be much less relevant for the more flexible cyclopentane derivatives. One factor that could speak against good regioselectivity in this case would be the fact that

Sordarin, an antifungal agent with a unique mode of action

• Huan Liang

Beilstein J. Org. Chem. 2008, 4, No. 31, doi:10.3762/bjoc.4.31

• subunits of the aglycone have been described by Cuevas and by Ciufolini. Highlights of these contributions are outlined below. Cuevas’s cyclopentane analog Modeling studies by Cuevas et al. relying on the INSIGHT software [43][44] reduced the tetracyclic framework of sordarin to a simple cyclopentane

• derivative 62 (Scheme 12), which contains aldehyde, carboxylic acid and hydroxymethyl groups as pharmacophores. The dihedral angles of CHO-CH2-CH2-COOH in the cyclopentane analog are very close to those of the carbon skeleton in sordaricin. The synthesis of 62 started with commercially available (+)-3,9

• compared to sordaricin (2) the cyclopentane analogs showed generally reduced potency towards a C. albicans protein synthesis assay, as well as diminished suppression of C. albicans cell growth, some analogs were actually more potent in certain tests. For instance, analogs 74, 78, 83 were all more potent

Allylsilanes in the synthesis of three to seven membered rings: the silylcuprate strategy

• Asunción Barbero,
• Francisco J. Pulido and
• M. Carmen Sañudo

Beilstein J. Org. Chem. 2007, 3, No. 16, doi:10.1186/1860-5397-3-16

• oxocompounds provides an easy entry to the synthesis of oxoallylsilanes 3–8 which are useful synthons for cyclopentane annulations (Scheme 2). [7][9] Acid chlorides react with 2 affording divinyl ketones 9–10. Allylsilanes 3–8 carrying an electrophilic carbonyl moiety readily undergo intramolecular cyclization

• -1-ones 15–16 (Scheme 3), which are not easily prepared by classical methods, and for which few methods of synthesis have been reported in the literature. [7][13] Silylcupration of acetylenes is also a powerful tool for cyclopentane annulations. Terminal alkynes 17–19 bearing electron-withdrawing