Phylogenomic analyses and distribution of terpene synthases among Streptomyces

• Lara Martín-Sánchez,
• Kumar Saurabh Singh,
• Mariana Avalos,
• Gilles P. van Wezel,
• Jeroen S. Dickschat and
• Paolina Garbeva

Beilstein J. Org. Chem. 2019, 15, 1181–1193, doi:10.3762/bjoc.15.115

• crystal structure of 2-MIB synthase. The function of this domain is unknown, but it is conserved in most 2-MIB synthases and not present in any other terpene synthase [20][28]. epi-Isozizaene (3) is a tricyclic sesquiterpene precursor of the antibiotic albaflavenone (17) (Scheme 3) [29]. Furthermore, both

Switchable selectivity in Pd-catalyzed [3 + 2] annulations of γ-oxy-2-cycloalkenones with 3-oxoglutarates: C–C/C–C vs C–C/O–C bond formation

• Yang Liu,
• Julie Oble and
• Giovanni Poli

Beilstein J. Org. Chem. 2019, 15, 1107–1115, doi:10.3762/bjoc.15.107

• long-term project dedicated to domino sequences [16][17][18][19][20][21][22] and Pd-catalyzed transformations [23][24][25][26][27][28][29][30], we recently reported a Pd(0)-catalyzed synthesis of bi- and tricyclic structures incorporating pyrrolidone rings (Scheme 1) [31]. In this transformation

Intramolecular cascade annulation triggered by rhodium(III)-catalyzed sequential C(sp²)–H activation and C(sp³)–H amination

• Liangliang Song,
• Guilong Tian,
• Johan Van der Eycken and
• Erik V. Van der Eycken

Beilstein J. Org. Chem. 2019, 15, 571–576, doi:10.3762/bjoc.15.52

• in one operational step. The tricyclic indolizinone scaffold is abundantly present in natural products, as, e.g., in the pharmacologically relevant mappicine [23][24], camptothecin [25][26], 10-hydroxycamptothecin and topotecan [27][28] (Figure 1). In 2012, Park and co-workers reported a RhIII

• (Scheme 1b) [29][30][31]. Inspired by this work, we envisaged that tricyclic indolizinones could be built through rhodium(III)-catalyzed sequential C(sp2)–H activation and C(sp3)–H amination of O-substituted N-hydroxyacrylamides (Scheme 1c). Results and Discussion We selected N-hydroxyacrylamide 1a as our

• molecules for further studies. Selected examples of natural products with a tricyclic indolizinone scaffold. Previous work and this approach. Reaction scope. Reaction conditions: 1 (0.3 mmol), [RhCp*Cl2]2 (0.015 mmol), CsOAc (0.6 mmol), 1,4-dioxane (3.0 mL), the ratio of isolated 3:2 was shown in

Synthesis of 1,2-divinylcyclopropanes by metal-catalyzed cyclopropanation of 1,3-dienes with cyclopropenes as vinyl carbene precursors

• Jesús González,
• Alba de la Fuente,
• María J. González,
• Laura Díez de Tejada,
• Luis A. López and
• Rubén Vicente

Beilstein J. Org. Chem. 2019, 15, 285–290, doi:10.3762/bjoc.15.25

• feasibility of an analogous reaction with 1,3-dienes preparing dienylcyclopropene 4. While treatment of 4 with ZnCl2 led to complex mixtures, likely due to the Lewis acid sensitivity of the benzylic cyclopropenylcarbinol moiety, the use of [Rh2(OAc)4] (1.0 mol %, CH2Cl2, rt) led to the tricyclic compound 5 in

Computational characterization of enzyme-bound thiamin diphosphate reveals a surprisingly stable tricyclic state: implications for catalysis

• Ferran Planas,
• Michael J. McLeish and
• Fahmi Himo

Beilstein J. Org. Chem. 2019, 15, 145–159, doi:10.3762/bjoc.15.15

• catalytically inactive tricyclic state. Conversely, the inhibitor binding greatly destabilized the ylide formation. Together, these observations have significant implications for the reaction kinetics of the ThDP-dependent enzymes, and, potentially, for the use of unnatural substrates in such reactions

• ], cyclohexane dione hydrolase [38], oxalyl-CoA decarboxylase [39], DXP synthase [40] and transketolase [41][42]. It is surprising that almost none of these studies acknowledged that there is a second, albeit less well discussed, path for the ThDP cofactor, i.e., the formation of a tricyclic, dihydrothiachromine

• species from the AP form [43][44][45]. Nucleophilic attack of N4′ on C2 results in the formation of a C2–N4′ bond, giving rise to the tricyclic intermediate TCH+. Loss of the N1′ proton TCH+ will result in the TC form of the cofactor [45]. While admittedly not common, the tricyclic form of the cofactor

Synthesis, biophysical properties, and RNase H activity of 6’-difluoro[4.3.0]bicyclo-DNA

• Sibylle Frei,
• Adam K. Katolik and
• Christian J. Leumann

Beilstein J. Org. Chem. 2019, 15, 79–88, doi:10.3762/bjoc.15.9

• -DNA (6’-diF-bc4,3-DNA). The difluorinated thymidine phosphoramidite building block was synthesized starting from an already known gem-difluorinated tricyclic glycal. This tricyclic siloxydifluorocyclopropane was converted into the [4.3.0]bicyclic nucleoside via cyclopropane ring-opening through the

• the presence of persilylated thymine to produce the iodine intermediates 2α/β (Scheme 1, Table 1, entry 1). These instable intermediates were then directly reduced with tributyltin hydride (Bu3SnH) to yield the tricyclic nucleosides 5α/β as main compounds. However, we observed the occurrence of the

• mechanism came from the outcome of the reaction where a tricyclic sugar was first treated with NIS and then with Bu3SnH resulting as expected in a gem-difluorinated bicyclic sugar (Scheme S1, Supporting Information File 1). This reaction also ruled out the involvement of the nucleobase or the iodine at the

6’-Fluoro[4.3.0]bicyclo nucleic acid: synthesis, biophysical properties and molecular dynamics simulations

• Sibylle Frei,
• Andrei Istrate and
• Christian J. Leumann

Beilstein J. Org. Chem. 2018, 14, 3088–3097, doi:10.3762/bjoc.14.288

• unsaturated 6’-fluoro[4.3.0]bicyclo nucleotides (6’F-bc4,3-DNA). Two 6’F-bc4,3 phosphoramidite building blocks (T and C) were synthesized starting from a previously described [3.3.0]bicyclic sugar. The conversion of this sugar to a gem-difluorinated tricyclic intermediate via difluorocarbene addition followed

• either by a NIS-mediated or Vorbrüggen nucleosidation yielded in both cases the β-tricyclic nucleoside as major anomer. Subsequent desilylation and cyclopropane ring opening of these tricyclic intermediates afforded the unsaturated 6’F-bc4,3 nucleosides. The successful incorporation of the corresponding

• duplexes. Results and Discussion Synthesis of the phosphoramidite building blocks Our strategy for the construction of the two phosphoramidite building blocks 10 and 16 envisaged as a key step the formation of a [4.3.0]bicyclic fluoroenone from a tricyclic siloxydifluorocyclopropane through a ring

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• example of organophotoredox catalysts. A carbazole is an aromatic tricyclic organic compound with two six-membered benzene rings fused on either side of a five-membered nitrogen-containing ring. They exhibit unusual optical and electronic properties such as photoconductivity and photorefractivity [77

Green synthesis of new chiral 1-(arylamino)imidazo[2,1-a]isoindole-2,5-diones from the corresponding α-amino acid arylhydrazides in aqueous medium

• Nadia Bouzayani,
• Jamil Kraїem,
• Sylvain Marque,
• Yakdhane Kacem,
• Abel Carlin-Sinclair,
• Jérôme Marrot and
• Béchir Ben Hassine

Beilstein J. Org. Chem. 2018, 14, 2923–2930, doi:10.3762/bjoc.14.271

• . The reaction is totally diastereoselective and gives access to the nitrogenated tricyclic core with a relative trans stereochemistry. Keywords: sodium dodecyl sulfate; totally diastereoselective; trans-stereochemistry; Introduction Tricyclic compounds, such as imidazo[2,1-a]isoindol-5-ones, are

• optimized conditions. A variety of the 1-(arylamino)imidazo[2,1-a]isoindole-2,5-diones 5b–m were prepared and the obtained results are summarized in Scheme 4. The mild conditions of the reaction gave access to the tricyclic compounds 5a–m providing similar yields, regardless the amino acid residue is. A

• aspect. Once more, the processing includes this eco-friendly way up to have the compounds in hand since simple precipitation allows to isolate the nitrogenated tricyclic compounds; no purification is needed. The model for the key step of the cyclization clearly explains the stereochemistries, which are

DABCO- and DBU-promoted one-pot reaction of N-sulfonyl ketimines with Morita–Baylis–Hillman carbonates: a sequential approach to (2-hydroxyaryl)nicotinate derivatives

• Soumitra Guin,
• Raman Gupta,
• Debashis Majee and
• Sampak Samanta

Beilstein J. Org. Chem. 2018, 14, 2771–2778, doi:10.3762/bjoc.14.254

• ' fashion to make a very reactive allyl ammonium intermediate 6. The latter further involves in the SN2' reaction with in situ generated carbanion intermediate 1a' forming SN2-adduct 3a. It undergoes an intramolecular aza-Michael reaction in the presence of DABCO, leading to tricyclic product 4a. For the

Domino ring-opening–ring-closing enyne metathesis vs enyne metathesis of norbornene derivatives with alkynyl side chains. Construction of condensed polycarbocycles

• Ritabrata Datta and
• Subrata Ghosh

Beilstein J. Org. Chem. 2018, 14, 2708–2714, doi:10.3762/bjoc.14.248

• derivative 2 would provide the tricyclic 1,3-diene 3 which on Diels–Alder reaction with a dienophile would enable access to condensed polycyclic structures 4 (Scheme 2). Thus an appropriately chosen norbornene derivative and a dienophile may provide the B/C/D/E ring system of retigeranic acids. Herein we

Targeting the Pseudomonas quinolone signal quorum sensing system for the discovery of novel anti-infective pathoblockers

• Christian Schütz and
• Martin Empting

Beilstein J. Org. Chem. 2018, 14, 2627–2645, doi:10.3762/bjoc.14.241

• by pqs QS, pyocyanin is one of the most prominent. This redox-active pigment is responsible for the greenish-blueish colour of P. aeruginosa cultures. It seems that generation of reactive oxygen species is a major mechanism of pyocyanin cytotoxicity [41]. This tricyclic compound is known to induce

Design and synthesis of C₃-symmetric molecules bearing propellane moieties via cyclotrimerization and a ring-closing metathesis sequence

• Sambasivarao Kotha,
• Saidulu Todeti and
• Vikas R. Aswar

Beilstein J. Org. Chem. 2018, 14, 2537–2544, doi:10.3762/bjoc.14.230

• ; propellane; ring-closing metathesis; Introduction In 1966 Ginsburg coined the word “propellane” [1][2] and Wiberg reviewed various aspects of medium and small ring propellanes [3][4]. Propellanes consist of tricyclic compounds where three rings are conjoined by a common C–C bond [1][5][6]. Heterocyclic

Quinolines from the cyclocondensation of isatoic anhydride with ethyl acetoacetate: preparation of ethyl 4-hydroxy-2-methylquinoline-3-carboxylate and derivatives

• Nicholas G. Jentsch,
• Jared D. Hume,
• Emily B. Crull,
• Samer M. Beauti,
• Amy H. Pham,
• Julie A. Pigza,
• Jacques J. Kessl and
• Matthew G. Donahue

Beilstein J. Org. Chem. 2018, 14, 2529–2536, doi:10.3762/bjoc.14.229

• . Structure–activity relationship studies have indicated that the 2-methyl and 3-acetic acid residues are crucial to maintaining the potency of this scaffold [10]. The Boehringer Ingelheim chemical development route toward the synthesis of quinoline 1 is shown in Scheme 1 [11]. The northern tricyclic

Practical tetrafluoroethylene fragment installation through a coupling reaction of (1,1,2,2-tetrafluorobut-3-en-1-yl)zinc bromide with various electrophiles

• Ken Tamamoto,
• Shigeyuki Yamada and
• Tsutomu Konno

Beilstein J. Org. Chem. 2018, 14, 2375–2383, doi:10.3762/bjoc.14.213

• the CF2CF2 unit between two cyclohexane rings caused significant enhancement in thermal stability in a liquid crystalline phase (Figure 1c) [11]. In addition to the development of a convenient access to CF2CF2-containing pyranoses [12], our group also showed that tricyclic mesogens with a CF2CF2

A novel and practical asymmetric synthesis of eptazocine hydrobromide

• Ruipeng Li,
• Zhenren Liu,
• Liang Chen,
• Jing Pan,
• Kuaile Lin and
• Weicheng Zhou

Beilstein J. Org. Chem. 2018, 14, 2340–2347, doi:10.3762/bjoc.14.209

• Mannich reaction to construct the tricyclic framework of 6. The study started with the alkylation under catalysis of 3 in a two-phase system of chlorobenzene and 50% aqueous NaOH solution based on our previous report [14]. When the reaction was run at 0–5 °C, an excellent yield (70%) and enantiomeric

• -methyl-7-methoxy-2-tetralone and a Mannich reaction to construct the tricyclic compound in eight linear steps. The optimization of reaction conditions were carried out to get a practical route delivering the product in excellent yield and purity (>99%). Experimental All solvents and reagents were from

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

• %. Further irradiation of hydrazones derived from furan-fused tricyclic diazocyclopentanediones culminates in the cycloelimination of furans to yield 2-N-(alkyl)hydrazone of cyclopentene-1,2,3-trione. By contrast, the direct photolysis of carbocyclic diazodiketones gives only Wolff rearrangement products

• compounds. The main objective of our current research was to elucidate the possibility of using carbocyclic diazodiketones in this photochemical process. For this purpose, diazocyclopentanediones 1a–g were tested in the study including unsubstituted diazocyclopentanedione 1a, tricyclic diazodiketones 1b–e

• ][39]. The structures of diazodiketones 1a–g were established using a standard set of spectroscopic methods (1Н and 13С NMR, IR and UV; for details, see Supporting Information File 1, Table S1) and in the case of the tricyclic diazodiketone 1с the structure was also confirmed by means of X-ray analysis

Synthesis of 9-arylalkynyl- and 9-aryl-substituted benzo[b]quinolizinium derivatives by Palladium-mediated cross-coupling reactions

• Siva Sankar Murthy Bandaru,
• Darinka Dzubiel,
• Heiko Ihmels,
• Mohebodin Karbasiyoun,
• Mohamed M. A. Mahmoud and
• Carola Schulzke

Beilstein J. Org. Chem. 2018, 14, 1871–1884, doi:10.3762/bjoc.14.161

• engage in π···π donor–acceptor attractions with the pyridinium moiety (outer most ring of the tricyclic moiety) and the two positively charged nitrogen atoms are per se much further apart due to the larger intramolecular separation between the intermolecularly interacting π-systems. In addition, the

Synthesis of new tricyclic 5,6-dihydro-4H-benzo[b][1,2,4]triazolo[1,5-d][1,4]diazepine derivatives by [3⁺ + 2]-cycloaddition/rearrangement reactions

• Lin-bo Luan,
• Zi-jie Song,
• Zhi-ming Li and
• Quan-rui Wang

Beilstein J. Org. Chem. 2018, 14, 1826–1833, doi:10.3762/bjoc.14.155

• Lin-bo Luan Zi-jie Song Zhi-ming Li Quan-rui Wang Department of Chemistry, Fudan University, 2005 Songhu Road, Fudan University, Shanghai 200438, People’s Republic of China 10.3762/bjoc.14.155 Abstract Two new series of tricyclic heterocycles, namely 5,6-dihydro-4H-benzo[b][1,2,4]triazolo[1,5-d

• furnishing the tricyclic 1,2,4-triazole-fused 1,4-benzodiazepines. Keywords: 1,4-benzodiazepine (BDZ); cyclization; hydrazones; oxidation; rearrangement; Introduction Heterocyclic compounds comprising a 1,4-benzodiazepine (BDZ) ring have been a topic of continued interest as they exhibit a wide spectrum of

• , we wish to describe the synthesis of unprecedented tricyclic heterocycles, i.e., 5,6-dihydro-4H-benzo[b][1,2,4]triazolo[1,5-d][1,4]diazepinium salts 10 and the related neutral free base derivatives 13 via the cationic [3+ + 2]-cycloaddition/rearrangement reactions using the bicyclic 4-acetoxy-4-azo

Synthesis of spirocyclic scaffolds using hypervalent iodine reagents

• Fateh V. Singh,
• Priyanka B. Kole,
• Saeesh R. Mangaonkar and
• Samata E. Shetgaonkar

Beilstein J. Org. Chem. 2018, 14, 1778–1805, doi:10.3762/bjoc.14.152

• ). Furthermore, spirolactam was used as intermediate in the synthesis of tricyclic compound 43 possessing a similar structure like that of the naturally occurring heterocyclic compound FR901483 [82]. Wardrop and co-workers [83] developed a new method for the preparation of 1-azaspiranes 47 by treatment of α- and

• ) in presence of 3.0 equivalents of TFA as an additive in dichloromethane (Scheme 17). The fused tricyclic compound 53 was obtained as major product in 55% yield along with the spiro compound 54 as a minor product in 8% yield. In 2009, Zhang and co-workers [89] reported an efficient method for the

• ). Furthermore, the absolute configuration of 88 was assigned by its single crystal X-ray analysis. 3.3. Application of spirolactams in natural product synthesis In 2001, Ciufolini and co-workers [103] employed PIDA (15) as an electrophile during the synthesis of naturally occurring tricyclic azaspirane

Metal-free formal synthesis of phenoxazine

• Gabriella Kervefors,
• Antonia Becker,
• Chandan Dey and
• Berit Olofsson

Beilstein J. Org. Chem. 2018, 14, 1491–1497, doi:10.3762/bjoc.14.126

• , unusually stable iodine(III) intermediate in the O-arylation was observed by NMR and could be converted to the product upon longer reaction time. Keywords: arylation; cyclization; diaryl ether; diaryliodonium salt; phenol; Introduction Phenoxazine (1) is a tricyclic compound consisting of an oxazine ring

A survey of chiral hypervalent iodine reagents in asymmetric synthesis

• Soumen Ghosh,
• Suman Pradhan and
• Indranil Chatterjee

Beilstein J. Org. Chem. 2018, 14, 1244–1262, doi:10.3762/bjoc.14.107

• spirocyclization of naphthol carboxylic acid [34]. Later Birman et al. reported a new variation of a chiral I(V) reagent, namely 2-(o-iodoxyphenyl)oxazoline derivative 28 [35]. The reagent was applied to an asymmetric [4 + 2] Diels–Alder dimerization of phenolic derivatives 29 to construct tricyclic derivatives 30

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

• ]. Transformation of adduct 31 to 11 starts with the synthesis of the stable cyclopropanoid tricyclic 32 from the reaction of the 7-oxabenzonorbornadiene 31 with dichlorocarbene, generated by the phase-transfer method. The thermolysis of dichloride 32 in nitrobenzene at 165 °C resulted in the formation of ring

• anhydride (204) to give a tricyclic adduct 207 (in 90% yield) (Scheme 35) [141][142]. Later, Middlemiss’ group also used dienophiles such as maleic anhydride (204), N-methylmaleimide (205), and N-phenylmaleimide (206) to give endo-adducts 207–209 [148]. Furthermore, these ethenobenzocycloheptenones 207–209

Iodine(III)-mediated halogenations of acyclic monoterpenoids

• Laure Peilleron,
• Tatyana D. Grayfer,
• Joëlle Dubois,
• Robert H. Dodd and
• Kevin Cariou

Beilstein J. Org. Chem. 2018, 14, 1103–1111, doi:10.3762/bjoc.14.96

• bromocarbocyclization of aryl-geranyl derivatives using a combination of iodine(III) oxidant and a bromide source. In this fashion, the reaction of homogeranylbenzene with bis(tert-butylcarbonyloxy)iodobenzene and triethylsilyl bromide, followed by acidic treatment led to a tricyclic brominated adduct (Scheme 1

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93