Ring-size-selective construction of fluorine-containing carbocycles via intramolecular iodoarylation of 1,1-difluoro-1-alkenes

• Takeshi Fujita,
• Ryo Kinoshita,
• Tsuyoshi Takanohashi,
• Naoto Suzuki and
• Junji Ichikawa

Beilstein J. Org. Chem. 2017, 13, 2682–2689, doi:10.3762/bjoc.13.266

• , we demonstrated selective constructions of six and seven-membered carbocyclic rings through the intramolecular iodoarylation of 3,3-difluoroallylic biaryls. The size selectivity in the cyclization was drastically controlled by the presence or absence of an aryl group in the 2-position of the 3,3

Conjugated nitrosoalkenes as Michael acceptors in carbon–carbon bond forming reactions: a review and perspective

• Yaroslav D. Boyko,
• Valentin S. Dorokhov,
• Alexey Yu. Sukhorukov and
• Sema L. Ioffe

Beilstein J. Org. Chem. 2017, 13, 2214–2234, doi:10.3762/bjoc.13.220

• to suppress side reactions and to use a stoichiometric amount of nucleophile. Under these conditions, Michael addition reactions with nitrosoalkenes can be realized in an intramolecular fashion that opens access to complex bridged and fused carbocyclic frameworks bearing several contiguous

• and ketones including cyclic ones were successfully used as nitrosoalkenes precursors to give oximes 8 in good to high yields. The same authors used the advantage of intramolecular Michael addition of enolates to nitrosoalkenes to construct bridged and fused carbocyclic systems [27]. For example, the

Synthesis of alkynyl-substituted camphor derivatives and their use in the preparation of paclitaxel-related compounds

• M. Fernanda N. N. Carvalho,
• Rudolf Herrmann and
• Gabriele Wagner

Beilstein J. Org. Chem. 2017, 13, 1230–1238, doi:10.3762/bjoc.13.122

• carbocyclic five-membered ring to the 2,3-position of the bicyclic camphor-derived moiety (Scheme 2a) [20]. Reactions of 4a with halogens (e.g., bromine) or acids were even more puzzling. In addition to the annulation, an unprecedented formation of a ketone accompanied by the reduction of sulphur took place

• the C–C bond between the atoms bearing the OH and NH groups (ring enlargement). The result is an isomerisation of 4a and 4b to form tricyclic compounds 7 containing a nine-membered carbocyclic ring (Scheme 3a) [27]. Isomerisations are the best examples for a perfect “atom economy” [28][29][30] since

• similarities (shown in red in Scheme 3) but also differences to our compounds obtained by Pt(II) catalysis from, e.g., 4a. The eye-catching dimethylmethylene bridge over the largest carbocyclic ring is of course the most striking similarity, although this ring is in our compounds one-carbon unit smaller (9 vs

Revaluation of biomass-derived furfuryl alcohol derivatives for the synthesis of carbocyclic nucleoside phosphonate analogues

• Bemba Sidi Mohamed,
• Christian Périgaud and
• Christophe Mathé

Beilstein J. Org. Chem. 2017, 13, 251–256, doi:10.3762/bjoc.13.28

• carbocyclic nucleoside methylphosphonate analogues bearing purine bases (adenine and guanine) was accomplished using bio-sourced furfuryl alcohol derivatives. All compounds were prepared using a Mitsunobu coupling between the heterocyclic base and an appropriate carbocyclic precursor. After deprotection, the

• compounds were evaluated for their activity against a large number of viruses. However, none of them showed significant antiviral activity or cytotoxicity. Keywords: analogue; antiviral; carbocyclic; nucleoside; phosphonate; Introduction Biomass is a valuable resource in search of renewable organic carbon

• some of the products have shown interesting antiviral activities. As part of our studies on carbocyclic nucleoside phosphonates [6] as potential anti-HIV agents [7][8], we envisioned to use bio-sourced racemic (+/−)-4-O-protected 2-cyclopentenone for the synthesis of hitherto unknown carbocyclic

A flow reactor setup for photochemistry of biphasic gas/liquid reactions

• Josef Schachtner,
• Patrick Bayer and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2016, 12, 1798–1811, doi:10.3762/bjoc.12.170

• . Following an optimized Schenck ene reaction procedure, N-methyl-1,2,3,6-tetrahydrophthalimide (1a) was reacted with molecular oxygen in the presence of methylene blue as sensitizer (Scheme 6). The resultant hydroperoxide motif (2a) constitutes a valuable carbocyclic building block. For reasons of

Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides

• Franziska Hemmerling and
• Frank Hahn

Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148

• ]. Their biosynthesis can be divided into three parts: the assembly of the PKS carbon backbone by a type II PKS including formation of the carbocyclic aromatic core, post-PKS modifications leading to the installation of the oxygen heterocycle and third, its modification by diverse tailoring enzymes [21][22

Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates

• Mohammad Haji

Beilstein J. Org. Chem. 2016, 12, 1269–1301, doi:10.3762/bjoc.12.121

• acetylenic aldehydes 102. The Kabachnik–Fields adducts of various carbocyclic acetylenic aldehydes 104 and 105 in the presence of AuBr3, PdCl2, AgOTf, AgNO3 or I+ underwent a 5-exo-dig cyclization to give dialkyl 1H-pyrrol-2-ylphosphonates 106. However, iodine-mediated cyclizations lead to pyrrol-1

Cyclisation mechanisms in the biosynthesis of ribosomally synthesised and post-translationally modified peptides

• Andrew W. Truman

Beilstein J. Org. Chem. 2016, 12, 1250–1268, doi:10.3762/bjoc.12.120

• , given that the active site Zn2+ is proposed to activate the cysteine side chains for cyclisation. The identification of the labyrinthopeptins [59] (Figure 4C) led to the discovery of a subset of class III lanthipeptides that contain an additional carbocyclic ring, which features the labionin (Lab) amino

Chiral cyclopentadienylruthenium sulfoxide catalysts for asymmetric redox bicycloisomerization

• Barry M. Trost,
• Michael C. Ryan and
• Meera Rao

Beilstein J. Org. Chem. 2016, 12, 1136–1152, doi:10.3762/bjoc.12.110

• requirements necessary to achieve high enantioselectivity. Indeed, when tosyl- or phosphoramidate-protected 1,6-enynes were tested, excellent yields and enantioselectivities were observed (Table 7). Like the Tris substrates, branching at the propargylic and alkenyl positions were well tolerated. Carbocyclic 69

The aminoindanol core as a key scaffold in bifunctional organocatalysts

• Isaac G. Sonsona,
• Eugenia Marqués-López and
• Raquel P. Herrera

Beilstein J. Org. Chem. 2016, 12, 505–523, doi:10.3762/bjoc.12.50

• hydroxy group) exhibited poor enantioselectivity. These effects may suggest and support the bifunctional role played by the catalyst (Figure 8). Diels–Alder reaction An important contribution in the construction of highly substituted carbocyclic compounds was disclosed by Tan’s group in 2009. In this work

Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions

• Rajeev S. Menon,
• Akkattu T. Biju and
• Vijay Nair

Beilstein J. Org. Chem. 2016, 12, 444–461, doi:10.3762/bjoc.12.47

• influence of these catalysts on the diastereoselectivity of the reaction was also studied using NMR techniques. An NHC-catalysed intramolecular benzoin condensation of carbohydrate-derived dialdehydes has been applied for the construction of carbocyclic sugars. Diastereoselective benzoin reactions of manno

Dynamic behavior of rearranging carbocations – implications for terpene biosynthesis

• Stephanie R. Hare and
• Dean J. Tantillo

Beilstein J. Org. Chem. 2016, 12, 377–390, doi:10.3762/bjoc.12.41

• a striking range of molecular architectures, varying in size and complexity (Figure 1) [1][2][3][4][5]. Some terpenes sport multiple stereogenic centers and multiple carbocyclic rings. These complex hydrocarbon frameworks are derived, however, from simple precursors lacking stereogenic centers and

Synthesis of Xenia diterpenoids and related metabolites isolated from marine organisms

• Tatjana Huber,
• Lara Weisheit and
• Thomas Magauer

Beilstein J. Org. Chem. 2015, 11, 2521–2539, doi:10.3762/bjoc.11.273

• cyclononane ring and isoprenyl side chain in their structure have been isolated. In general, the common structural feature of xenicanes is a bicyclic framework consisting of an A ring which is trans-fused to a nine-membered carbocyclic B ring. The family of Xenia diterpenoids was originally divided into three

• xeniaethers. An alternative biosynthetic pathway proposed by Schmitz and van der Helm involves the direct formation of the nine-membered carbocyclic ring via oxidative cyclization of geranyllinalool (34) [2], which is formed from GGPP (28) by enzymatic hydrolysis of the pyrophosphate unit and allylic

• –Kishi coupling of haloalkenes with aldehydes. The first synthesis of the unusual nine-membered carbocyclic ring was reported by Corey for the total synthesis of β-caryophyllene in 1963 (Scheme 4) [29][30][31]. Starting with a photochemical [2 + 2] cycloaddition between 2-cyclohexen-1-one (37) and

Copper-catalysed asymmetric allylic alkylation of alkylzirconocenes to racemic 3,6-dihydro-2H-pyrans

• Emeline Rideau and
• Stephen P. Fletcher

Beilstein J. Org. Chem. 2015, 11, 2435–2443, doi:10.3762/bjoc.11.264

• , Table 1). Interestingly, no product was formed using our previously reported conditions for AAA to racemic carbocyclic substrates (CuI, ligand A, CHCl3, Table 1, entry 1) [26] and only unreacted starting material was recovered. Different Cu salts were examined (Table 1, entries 2–7) and more strongly

• than all-carbocyclic 1, it appears that 2a undergoes kinetic resolution. However, this system is clearly complicated by the fact that the majority of 2a is consumed during byproduct 11's formation. In the phosphate system based on 2d, the ee of product 5 was found to increase during the course of the

Recent applications of ring-rearrangement metathesis in organic synthesis

• Sambasivarao Kotha,
• Milind Meshram,
• Priti Khedkar,
• Shaibal Banerjee and
• Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

• protocol to bicyclic isoxazolidine ring system. RRM approach toward the total synthesis of (±)-8-epihalosaline (300). Sequential RRM approach to decalin 304 and 7/6 fused 305 systems. RRM protocol to various fused carbocyclic derivatives. RRM to cis-hydrindenol derivatives. RRM protocol towards the cis

Spiro annulation of cage polycycles via Grignard reaction and ring-closing metathesis as key steps

• Sambasivarao Kotha,
• Mohammad Saifuddin,
• Rashid Ali and
• Gaddamedi Sreevani

Beilstein J. Org. Chem. 2015, 11, 1367–1372, doi:10.3762/bjoc.11.147

• architecturally intricate cage molecules is a worthwhile challenge. The unique properties associated with the carbocyclic cage frameworks are the main reasons for pursuing their synthesis [1][2]. They are valuable synthons to assemble natural as well as non-natural products [3][4]. In addition, the cage molecules

Development of variously functionalized nitrile oxides

• Haruyasu Asahara,
• Keita Arikiyo and
• Nagatoshi Nishiwaki

Beilstein J. Org. Chem. 2015, 11, 1241–1245, doi:10.3762/bjoc.11.138

• water occurred even at low temperatures because of the higher electron deficiency of the isoxazole ring compared with carbocyclic rings. When, instead of water, less nucleophilic acetic acid was employed for the quench, 12 was isolated in 74% yield and the competitive hydrolysis of 12 was suppressed (6

Hybrid macrocycle formation and spiro annulation on cis-syn-cis-tricyclo[6.3.0.0^2,6]undeca-3,11-dione and its congeners via ring-closing metathesis

• Sambasivarao Kotha,
• Ajay Kumar Chinnam and
• Rashid Ali

Beilstein J. Org. Chem. 2015, 11, 1123–1128, doi:10.3762/bjoc.11.126

• ][12][13][14][15][16][17][18][19][20][21]. Several approaches are available for the synthesis of carbocyclic quinanes, however, only a limited number of methods is available for oxa- [22][23][24][25] and aza-polyquinanes [26][27][28]. The indole unit is present in a variety of plant alkaloids (e.g

Synthesis of novel N-cyclopentenyl-lactams using the Aubé reaction

• Madhuri V. Shinde,
• Rohini S. Ople,
• Ekta Sangtani,
• Rajesh Gonnade and
• D. Srinivasa Reddy

Beilstein J. Org. Chem. 2015, 11, 1060–1067, doi:10.3762/bjoc.11.119

• , India 10.3762/bjoc.11.119 Abstract A novel and convenient method utilizing the Aubé reaction to access a new class of compounds that are similar to carbocyclic nucleosides is reported. The azido alcohol derived from Vince lactam undergoes the Aubé reaction with various cyclic ketones to give

• : Aubé reaction; biological activity; carbocyclic nucleosides; cyclopentenylated lactams; cyclopentylated lactams; Introduction One popular method for the synthesis of N-substituted lactams is the Aubé reaction [1][2][3][4]. Over the last few decades, this reaction has gained popularity and resulted in

• conjugates starting from an azido-alcohol embedded in sugar derivatives and cyclic ketones [16]. In continuation of this work (and also to expand the potential of this chemistry), a new class of compounds were prepared. These cyclopentenoid–lactams, which look like carbocyclic nucleosides, were prepared

On the strong difference in reactivity of acyclic and cyclic diazodiketones with thioketones: experimental results and quantum-chemical interpretation

• Andrey S. Mereshchenko,
• Alexey V. Ivanov,
• Viktor I. Baranovskii,
• Grzegorz Mloston,
• Ludmila L. Rodina and
• Valerij A. Nikolaev

Beilstein J. Org. Chem. 2015, 11, 504–513, doi:10.3762/bjoc.11.57

• , carbocyclic diazodiketones are much less reactive under similar conditions due to the locked cyclic structure and are unfavorable for the 1,3-dipolar cycloaddition due to the Z,Z-conformation of the diazo molecule. This structure results in high, positive values of the Gibbs free energy change for the first

• performed a detailed experimental study of reactions of a series of 2-diazo-1,3-dicarbonyl compounds 1 with aromatic and aliphatic thioketones 2, and it was established that they occurred in a varied manner: acyclic diazodicarbonyl compounds 1 readily reacted with thioketones 2, whereas carbocyclic

• calculations were the same diazodicarbonyl compounds and thioketones that were applied in the earlier experimental studies, namely: acyclic diazodiketones 1a,b, diazoketoester 1c, diazomalonate 1d, and carbocyclic diazodiketones 1e,f, along with thiobenzophenone (2a) and 2,2,4,4-tetramethyl-3

Design and synthesis of novel bis-annulated caged polycycles via ring-closing metathesis: pushpakenediol

• Sambasivarao Kotha and
• Mirtunjay Kumar Dipak

Beilstein J. Org. Chem. 2014, 10, 2664–2670, doi:10.3762/bjoc.10.280

• were found to be key structural elements in various drugs [10][11][12], high-energy materials [13][14][15] and supramolecules [16][17]. In addition, caged molecules possess unusual and often unique properties that are associated with their rigid carbocyclic framework [1][2]. They are useful synthons in

Regio- and stereoselective synthesis of new diaminocyclopentanols

• Evgeni A. Larin,
• Valeri S. Kochubei and
• Yuri M. Atroshchenko

Beilstein J. Org. Chem. 2014, 10, 2513–2520, doi:10.3762/bjoc.10.262

• (9H-purin-6-amine (7d)) attacks the oxirane carbon atom from the side of the carbocyclic ring where the N,N-disubstituted amino group is located, and this precludes the approach of the nucleophile to the C2 carbon atom because of sterical hindrance. Thus, C1 of 6a,b is the favoured site for the

Chiral phosphines in nucleophilic organocatalysis

• Yumei Xiao,
• Zhanhu Sun,
• Hongchao Guo and
• Ohyun Kwon

Beilstein J. Org. Chem. 2014, 10, 2089–2121, doi:10.3762/bjoc.10.218

• variety of methods for enantioselective syntheses of structurally diverse acyclic, carbocyclic, and heterocyclic compounds. 2.1 [3 + 2] Annulation of allenes with activated alkenes Nucleophilic phosphine-catalyzed annulations have been established as very useful tools for the syntheses of carbo- and

Application of cyclic phosphonamide reagents in the total synthesis of natural products and biologically active molecules

• Thilo Focken and
• Stephen Hanessian

Beilstein J. Org. Chem. 2014, 10, 1848–1877, doi:10.3762/bjoc.10.195

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

• -DNA molecular platform. In both modifications the torsion around C6’–C7’ within the carbocyclic ring is planarized by either the presence of a C6’–C7’ double bond or a cyclopropane ring. Structural analysis of these two nucleosides by X-ray analysis reveals a clear preference of torsion angle γ for

• torsion angle γ in the anticlinal range. The saturation of the carbocyclic ring translates to a lesser extent also into the furanose ring where a 1’-exo instead of a 2’-endo conformation is observed in bc-T. Both furanose conformations, however, belong to the S-type and are thus structurally related in

• γ and variability between S- and N-type in the furanose conformation, whereas rigidifying and planarizing the C6’–C7’-bond, as in 8β and 11β, leads to a synclinal torsion angle γ and a consistent 2’-endo furanose conformation. Saturation of the carbocyclic ring, as in bc-T, leads to an anticlinal