Simple synthesis of pyrrolo[3,2-e]indole-1-carbonitriles

• Adam Trawczyński,
• Robert Bujok,
• Zbigniew Wróbel and
• Krzysztof Wojciechowski

Beilstein J. Org. Chem. 2013, 9, 934–941, doi:10.3762/bjoc.9.107

• that the five-membered ring finally isomerizes to the N-hydroxypyrrole fragment of 6e. To remove the benzyloxymethyl group from the compound 8a we adopted the procedure proposed by Macor [6]. Heating 8a with ammonium formate and 10% palladium on carbon as a catalyst in isopropanol in a sealed tube (95

A computational study of base-catalyzed reactions of cyclic 1,2-diones: cyclobutane-1,2-dione

• Nargis Sultana and
• Walter M. F. Fabian

Beilstein J. Org. Chem. 2013, 9, 594–601, doi:10.3762/bjoc.9.64

• –C2 bonds and the oxygen atom O1 [α = 103° (TS4), 106° (Int4), and 112° (TS5)]. The product P3a of path C has a largely planar five-membered ring structure (α = 165°). In both TS4 and Int4 the C1–C2 distance (1.48 Å) is in the range of C–C single bonds, while in TS5 this bond is significantly

Intramolecular carbolithiation cascades as a route to a highly strained carbocyclic framework: competition between 5-exo-trig ring closure and proton transfer

• William F. Bailey and
• Justin D. Fair

Beilstein J. Org. Chem. 2013, 9, 537–543, doi:10.3762/bjoc.9.59

• reaction appears to provide an interesting … procedure for formation of five-membered ring systems which is potentially significant for synthetic purposes” [3]. Indeed, the facile cyclization of olefinic and acetylenic organolithiums has proven to be a regiospecific and highly stereoselective route [4] to

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

• charge at the nitrogen atom. Similarly, C3–C4, at 1.342(2) Å, is also a (marginally lengthened) double bond. The C–S bond lengths in the five-membered ring are approximately equal [1.727(1) – 1.746(1) Å]. The new 1,3-dithiolium cations are particularly prone to nucleophilic attack at their 2-positions

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

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

Binaphthyl-anchored antibacterial tripeptide derivatives with hydrophobic C-terminal amino acid variations

• John B. Bremner,
• Paul A. Keller,
• Stephen G. Pyne,
• Mark J. Robertson,
• K. Sakthivel,
• Kittiya Somphol,
• Dean Baylis,
• Jonathan A. Coates,
• John Deadman,
• Dharshini Jeevarajah and
• David I. Rhodes

Beilstein J. Org. Chem. 2012, 8, 1265–1270, doi:10.3762/bjoc.8.142

• assessing the effect of variation in the spatial disposition of the cycloalkyl or oxacycloalkyl ring on antibacterial activity. The conformationally less restricted gem diethyl-substituted compound 2g was also targeted in order to make antibacterial activity comparisons with the five-membered ring analogue

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

• Robert Hilgraf,
• Nicole Zimmermann,
• Lutz Lehmann,
• Armin Tröger and
• Wittko Francke

Beilstein J. Org. Chem. 2012, 8, 1256–1264, doi:10.3762/bjoc.8.141

• mitsugashiwalactone (25) [42] and its “nor-iridomyrmecin-complement” boschnialactone (26), [43] which all are plant volatiles, the methyl group in the typical five-membered ring of iridoids keeps its (S)-configuration (see also Figure 8), which is just in contrast to X and Z [44]. However, recently, two stereoisomers

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

• few others, the stereogenic center carrying the methyl group in the five-membered ring of iridoid lactones including insect semiochemicals [13][14][15] generally shows (S)-configuration. Only recently, two isomeric iridoid lactones showing (7R)-configuration have been identified from the Drosophila

• may turn out that the chiral center carrying the methyl group in the five-membered ring of iridoids may much more often show (R)-configuration than it is known today. Terpenoids 1–5 present in Alloxysta victrix and cis-fused bicyclic iridoids known from other insects (6–8). 70 eV EI-mass spectrum of

Synthesis and characterization of Sant-75 derivatives as Hedgehog-pathway inhibitors

• Chao Che,
• Song Li,
• Bo Yang,
• Shengchang Xin,
• Zhixiong Yu,
• Taofeng Shao,
• Chuanye Tao,
• Shuo Lin and
• Zhen Yang

Beilstein J. Org. Chem. 2012, 8, 841–849, doi:10.3762/bjoc.8.94

• various heteroaryl acids 8a–h to yield 9a–h (Scheme 4). The following considerations were taken for the selection of the heteroaryl acids: removal of the Cl atom (8a); replacement of the S atom with N or O atoms (8b, 8c); two heteroatoms in a five-membered ring (8d–f); and a 5,5-fused ring heterocycle (8h

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

• double bond of the substrate. It is worth mentioning that in our earlier work on similar compounds [19], we isolated at least two isomers of 4 (with the methine hydrogen atom at the five-membered ring being present at either the α or β position). In our earlier work [10], carbene addition to similar

• , which was recrystallized from hexane and dichloromethane to afford single crystals suitable for X-ray analysis. The X-ray data [20] showed that the central, six-membered ring is almost planar but is slightly folded about the axis C(2)···C(6); the five-membered ring is essentially planar. The two larger

Synthesis and biological evaluation of nojirimycin- and pyrrolidine-based trehalase inhibitors

• Davide Bini,
• Francesca Cardona,
• Matilde Forcella,
• Camilla Parmeggiani,
• Paolo Parenti,
• Francesco Nicotra and
• Laura Cipolla

Beilstein J. Org. Chem. 2012, 8, 514–521, doi:10.3762/bjoc.8.58

• synthesized with different stereochemistry on the five-membered ring (i.e., compounds 14, 16 versus 17, 19, Figure 3), in order to elucidate whether this feature could be relevant for enzyme recognition, and with a sterically demanding alkyl chain positioned either at the nitrogen atom or at the adjacent

Perhydroazulene-based liquid-crystalline materials with smectic phases

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

Beilstein J. Org. Chem. 2012, 8, 403–410, doi:10.3762/bjoc.8.44

• , obtained in >98% purity, and characterized by NMR spectroscopy as well as by their other analytical data [14]. The NMR data of 1a and 1b indicate that methylene groups in the five-membered ring carry pairwise enantiotopic and diastereotopic H-atoms; enantiotopic with respect to the internal mirror plane

Directed aromatic functionalization in natural-product synthesis: Fredericamycin A, nothapodytine B, and topopyrones B and D

• Charles Dylan Turner and
• Marco A. Ciufolini

Beilstein J. Org. Chem. 2011, 7, 1475–1485, doi:10.3762/bjoc.7.171

• cyanopyridones 39b instead. In keeping with a principle introduced during our work on camptothecin [81][82][83], the five-membered ring of 36 was imagined to result upon acid treatment of 40 (Scheme 8) [84], which in turn could be assembled by using the chemistry of Scheme 8 on substrate 41, provided that the

Amines as key building blocks in Pd-assisted multicomponent processes

• Didier Bouyssi,
• Nuno Monteiro and
• Geneviève Balme

Beilstein J. Org. Chem. 2011, 7, 1387–1406, doi:10.3762/bjoc.7.163

• -allylpalladium intermediate that would lead to 2,5-dihydropyrrole or vinylic azacyclopropane derivatives. This is followed by a five-membered ring cyclization leading to polysubstituted imidazolidinones 75 in rather good yields and excellent selectivity (Scheme 32). A conceptually related strategy was developed

Metathesis access to monocyclic iminocyclitol-based therapeutic agents

• Ileana Dragutan,
• Valerian Dragutan,
• Carmen Mitan,
• Hermanus C.M. Vosloo,
• Lionel Delaude and
• Albert Demonceau

Beilstein J. Org. Chem. 2011, 7, 699–716, doi:10.3762/bjoc.7.81

• . Its synthesis, as well as that of its dihydroxylated homologue 36, features as the key step five-membered ring formation via RCM induced by the 2nd-generation Grubbs catalyst 5 (Scheme 6) [58]. A further contribution to new pyrrolidine-based azasugars, characteristically having 1,2-dihydroxyethyl side

Advances in synthetic approach to and antifungal activity of triazoles

• Kumari Shalini,
• Nitin Kumar,
• Sushma Drabu and
• Pramod Kumar Sharma

Beilstein J. Org. Chem. 2011, 7, 668–677, doi:10.3762/bjoc.7.79

• Kumari Shalini Nitin Kumar Sushma Drabu Pramod Kumar Sharma Department of Pharmaceutical Technology, Meerut Institute of Engineering & Technology, Meerut, U. P., India, Pin-250005 Director, M.S.I.P., Janakpuri, New Delhi, India 10.3762/bjoc.7.79 Abstract Several five membered ring systems, e.g

• azoles are a class of synthetic compounds that possess one or more azole rings. Whilst both imidazole and triazole are five membered ring heterocycles, imidazole contains two ring nitrogen atoms, whereas triazoles have three. However, compared with imidazoles (clotrimazole, ketoconazole, miconazole

• agents posaconazole (12) and ravuconazole (13)) are synthetic compounds that have one or more azole rings with three nitrogen atoms in a five membered ring. They act by inhibition of the cytochrome P450-dependent conversion of lanosterol to ergosterol [42]. Triazoles act as cytochrome P450 14α

Gold-catalyzed heterocyclizations in alkynyl- and allenyl-β-lactams

• Benito Alcaide and
• Pedro Almendros

Beilstein J. Org. Chem. 2011, 7, 622–630, doi:10.3762/bjoc.7.73

• exclusively β-lactam–tetrahydrofuran hybrids 6 in good isolated yields (Scheme 3). Besides total chemocontrol, the reaction was regiospecific and only the five-membered ring ether was formed: The isomeric six-membered ring product was not observed. By contrast, when the cyclization of olefinic α-allenols 5

Construction of cyclic enones via gold-catalyzed oxygen transfer reactions

• Leping Liu,
• Bo Xu and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2011, 7, 606–614, doi:10.3762/bjoc.7.71

• -membered ring oxonium intermediate C than for the seven-membered ring oxonium A. This energetic preference is also observed in the stabilities of the oxoniums themselves, with C considerably more stable by 16.1 kcal/mol. The subsequent transformations are all computed to be feasible, with the barrier to [4

• accordance with the experimental findings, the [4 + 2] pathway is found to be the more favorable. The rate-limiting step in each pathway is the intramolecular nucleophilic addition to the Au-coordinated alkyne – the barrier for this step is computed to be 6.8 kcal/mol lower for the formation of the five

The arene–alkene photocycloaddition

• Ursula Streit and
• Christian G. Bochet

Beilstein J. Org. Chem. 2011, 7, 525–542, doi:10.3762/bjoc.7.61

• derivative would lead initially to the formation of the four-membered ring. The five-membered ring will be preferred but the radical formed cannot recombine and fragments back to the starting material. Once the four-membered ring containing a primary exocyclic radical is formed, recombination either directly

Synthesis of 5-(2-methoxy-1-naphthyl)- and 5-[2-(methoxymethyl)-1-naphthyl]-11H-benzo[b]fluorene as 2,2'-disubstituted 1,1'-binaphthyls via benzannulated enyne–allenes

• Yu-Hsuan Wang,
• Joshua F. Bailey,
• Jeffrey L. Petersen and
• Kung K. Wang

Beilstein J. Org. Chem. 2011, 7, 496–502, doi:10.3762/bjoc.7.58

• methylene hydrogens on the five-membered ring. AB systems from the methylene hydrogens were also observed in other similar 11H-benzo[b]fluorenyl structures [7][22][23][24]. The AB pattern remained unchanged at 70 °C, suggesting a relatively slow rate of rotation, on the NMR time scale, around the carbon

• methoxy group. The signals of the methylene hydrogens on the five-membered ring could barely be discerned as an AB system with the two inner signals overlapped at δ 4.51 and two small outer signals at δ 4.55 and 4.47. The rotational barrier of the parent 1,1'-binaphthyl in N,N-dimethylformamide was

• spectrometer, the signals of the methylene hydrogens on the five-membered ring could be discerned as an AB system at δ 4.27 (J = 21 Hz) and 4.25 (J = 21 Hz). The rotational barrier of BINOL as a member of the 2,2'-disubstituted 1,1'-binaphthyls was determined to be 37.2 kcal/mol at 195 °C in naphthalene

Palladium-catalyzed formation of oxazolidinones from biscarbamates: a mechanistic study

• Benan Kilbas and
• Metin Balci

Beilstein J. Org. Chem. 2011, 7, 246–253, doi:10.3762/bjoc.7.33

• assigned from 1H (COSY, HSQC, HMBC) and 13C NMR spectroscopic data. The most conspicuous features in the 1H NMR spectrum of this compound were the five-membered ring proton resonances. The proton H-6b adjacent to the oxygen atom resonates at 5.12 ppm as a doublet of doublets, (J6b,3a = 7.8 Hz, J6b,6a = 1.4

A surprising new route to 4-nitro-3-phenylisoxazole

• Henning Hopf,
• Aboul-fetouh E. Mourad and
• Peter G. Jones

Beilstein J. Org. Chem. 2010, 6, No. 68, doi:10.3762/bjoc.6.68

• 1.4283(13), O1–C5 1.2202(15) Å) may be considered normal. The five-membered ring is planar within a mean deviation of 0.002 Å, and subtends interplanar angles of 6.5° with the nitro and (in the same sense) 58.4° with the phenyl substituent. Molecules are connected to form broad ribbons in the (101) plane

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

Pd/C-mediated synthesis of α-pyrone fused with a five-membered nitrogen heteroaryl ring: A new route to pyrano[4,3-c]pyrazol-4(1H)-ones

• Dhilli Rao Gorja,
• Venkateswara Rao Batchu,
• Ashok Ettam and
• Manojit Pal

Beilstein J. Org. Chem. 2009, 5, No. 64, doi:10.3762/bjoc.5.64

• shown anticancer properties in vitro [7]. Recently, incorporation of another five-membered ring, e.g. pyrazole pyrone moieties in a single molecule (A, Figure 1) has been reported to provide polycyclic azaheteroaromatics with a steroid-like skeleton [8]. This initiative was based on the assumption that

Synthesis of (S)-1-(2-chloroacetyl)pyrrolidine- 2-carbonitrile: A key intermediate for dipeptidyl peptidase IV inhibitors

• Santosh K. Singh,
• Narendra Manne and
• Manojit Pal

Beilstein J. Org. Chem. 2008, 4, No. 20, doi:10.3762/bjoc.4.20

• -cells [1]. Because of its key role in DPP-IV inhibition the 2(S)-cyanopyrrolidine moiety has been found to be an integral part of many DPP-IV inhibitors (Figure 1). Apart from behaving as a proline mimic, the presence of the nitrile on the five-membered ring provides (i) reversible and nanomolar