An effective one-pot access to polynuclear dispiroheterocyclic structures comprising pyrrolidinyloxindole and imidazothiazolotriazine moieties via a 1,3-dipolar cycloaddition strategy

• Alexei N. Izmest’ev,
• Galina A. Gazieva,
• Natalya V. Sigay,
• Sergei A. Serkov,
• Valentina A. Karnoukhova,
• Vadim V. Kachala,
• Alexander S. Shashkov,
• Igor E. Zanin,
• Angelina N. Kravchenko and
• Nina N. Makhova

Beilstein J. Org. Chem. 2016, 12, 2240–2249, doi:10.3762/bjoc.12.216

• compounds having the spiropyrrolidinyloxindole core [14][15][16][17][18]. The 3,3’-spiropyrrolidinyloxindole unit is found in the molecular skeleton of a large family of natural alkaloids with remarkable bioactivity profiles and interesting structural properties [19][20]. Derivatives with the 2,3

Chiral ammonium betaine-catalyzed asymmetric Mannich-type reaction of oxindoles

• Masahiro Torii,
• Kohsuke Kato,
• Daisuke Uraguchi and
• Takashi Ooi

Beilstein J. Org. Chem. 2016, 12, 2099–2103, doi:10.3762/bjoc.12.199

• quaternary and tertiary stereogenic carbon centers on biologically intriguing molecular frameworks with high fidelity. Keywords: ammonium betaine; asymmetric catalysis; Mannich reaction; organocatalysis; oxindole; Introduction Chiral indole alkaloids possessing C-3 quaternary indoline frameworks are an

Varioloid A, a new indolyl-6,10b-dihydro-5aH-[1]benzofuro[2,3-b]indole derivative from the marine alga-derived endophytic fungus Paecilomyces variotii EN-291

• Peng Zhang,
• Xiao-Ming Li,
• Xin-Xin Mao,
• Attila Mándi,
• Tibor Kurtán and
• Bin-Gui Wang

Beilstein J. Org. Chem. 2016, 12, 2012–2018, doi:10.3762/bjoc.12.188

• variotii EN-291, an endophytic fungus isolated from the red alga Grateloupia turuturu. The investigation of the chemical constituents of this fungal strain had been performed and as a result, three new oxepine-containing alkaloids with antimicrobial activities [9][10], two new butenolide derivatives with

• DPPH radical scavenging activity [11], and two new prenylated indole alkaloids with cytotoxic activity [12] had been isolated and identified. In an effort to isolate additional analogues that might show similar effects, a larger fermentation was undertaken. This study led to the isolation of two

Unusual reactions of diazocarbonyl compounds with α,β-unsaturated δ-amino esters: Rh(II)-catalyzed Wolff rearrangement and oxidative cleavage of N–H-insertion products

• Valerij A. Nikolaev,
• Jury J. Medvedev,
• Olesia S. Galkina,
• Ksenia V. Azarova and
• Christoph Schneider

Beilstein J. Org. Chem. 2016, 12, 1904–1910, doi:10.3762/bjoc.12.180

• of aroyldiazomethanes 2 and dibenzoyldiazomethane 3c with aminoester 1. Oxidative functionalization of α-СН2-groups in the structure of amines is a rather familiar instrument of organic synthesis, which is widely used for the preparation of amino acids and alkaloids [26][27][28]. Cleavage of σ-С–С

A chiral analog of the bicyclic guanidine TBD: synthesis, structure and Brønsted base catalysis

• Mariano Goldberg,
• Denis Sartakov,
• Jan W. Bats,
• Michael Bolte and
• Michael W. Göbel

Beilstein J. Org. Chem. 2016, 12, 1870–1876, doi:10.3762/bjoc.12.176

• chiral counterions in less polar solvents. Up to 61% ee could be obtained using cinchona alkaloids as catalysts [26]. The subsequent work of Tan and co-workers with guanidine catalyst 8 achieved enantioselectivities as high as 99% ee [19]. In recent years functionalized chiral amines have been

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

• [4]. Oxygen heterocycles are mainly found in carbohydrates, polyketides, peptides and terpenoids. Nitrogen heterocycles are part of peptides and alkaloids. Both can of course also occur in the respective hybrid natural products. Sulphur-containing heterocycles are present in few polyketides and more

Synthesis of 2-oxindoles via 'transition-metal-free' intramolecular dehydrogenative coupling (IDC) of sp² C–H and sp³ C–H bonds

• Nivesh Kumar,
• Santanu Ghosh,
• Subhajit Bhunia and
• Alakesh Bisai

Beilstein J. Org. Chem. 2016, 12, 1153–1169, doi:10.3762/bjoc.12.111

• recently gained immense importance. 2-Oxindoles having all carbon quaternary centres at the pseudobenzylic position are common structural scaffolds in many naturally occurring alkaloids of biological relevance [22][23][24][25]. These heterocyclic motifs especially exist in indole alkaloids with a wide

• focussed our attention to prenylated, reverse-prenylated, and geranylated hexahydropyrrolo[2,3-b]indole alkaloids showing broad biological activities [55][56][57][58][59][60][61]. For the synthesis of these compounds, we thought of utilizing the Pd-catalyzed decarboxylative strategy to install the prenyl

• the results are summarized in Figure 5. Interestingly, under this conditions, we can synthesize a variety of 2-oxindoles 8 in moderate to good yields. There are a large number of indole alkaloids bearing a 3-arylated-2-oxindole moiety that are known for their various biological activities [65][66][67

Modular synthesis of the pyrimidine core of the manzacidins by divergent Tsuji–Trost coupling

• Sebastian Bretzke,
• Stephan Scheeff,
• Felicitas Vollmeyer,
• Friederike Eberhagen,
• Frank Rominger and
• Dirk Menche

Beilstein J. Org. Chem. 2016, 12, 1111–1121, doi:10.3762/bjoc.12.107

• alkaloids of marine origin. Additional features of this route include the stereoselective generation of the central amine core with an appending quaternary center by an asymmetric addition of a Grignard reagent to a chiral tert-butanesulfinyl ketimine following an optimized Ellman protocol and a cross

• bromopyrrole alkaloids has attracted great interest from synthetic chemists and a variety of elegant total syntheses has been reported [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Inspired by an innovative concept for heterocycles synthesis recently developed in our group [26][27][28][29

• the chiral amine core of these alkaloids. For the synthesis of the nitrogen appending the quaternary center we tested a method developed by the Ellman group [46][47], which relies on an asymmetric addition of organometallic reagents to enantiopure tert-butanesulfinyl ketimines of type 29 and 30

Towards the total synthesis of keramaphidin B

• Pavol Jakubec,
• Alistair J. M. Farley and
• Darren J. Dixon

Beilstein J. Org. Chem. 2016, 12, 1096–1100, doi:10.3762/bjoc.12.104

• murine leukemia cells (IC50 0.28 μg/mL) [1]. It is a member of the manzamine alkaloids and has an exquisite molecular structure comprising a 6,6,6,11,13 pentacycle possessing 4 stereogenic centres including one quaternary centre (Figure 1). In 1992, two years before its isolation, Baldwin and Whitehead

• , in their landmark paper entitled ‘On the Biosynthesis of Manzamines’ postulated that keramaphidin B was a common intermediate in the biosynthesis of the manzamine alkaloids [2]. Several years later, Baldwin and co-workers synthesised keramaphidin B following a biomimetic pathway via an intramolecular

• manzamine alkaloids with a particular emphasis on the development of novel catalytic methods for simplifying their syntheses [5][6][7][8][9][10]. Owing to keramaphidin B’s attractive structure combined with its interesting biological profile and the lack of an efficient method for its synthesis, we selected

Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• catalysts Cinchona alkaloids and their derivatives have been widely used as chiral catalysts in many reactions [44] and also show synthetic utilities in the synthesis of enantiomerically pure 3-substituted 3-hydroxyoxindoles. In 2013, Wu and co-workers reported the cinchona alkaloid (cat. 14)-catalyzed

1H-Imidazol-4(5H)-ones and thiazol-4(5H)-ones as emerging pronucleophiles in asymmetric catalysis

• Antonia Mielgo and
• Claudio Palomo

Beilstein J. Org. Chem. 2016, 12, 918–936, doi:10.3762/bjoc.12.90

• acceptors in reactions promoted by bifunctional Brønsted bases. 1.2.1 Nitroalkenes as acceptors. Investigation of the base-catalyzed Michael addition reaction of 2-thio-1H-imidazol-4(5H)-ones 4 to nitroalkenes 5 [55] revealed that cinchona alkaloids such as quinine, (DHQ)2Pyr or even thiourea tertiary amine

Indenopyrans – synthesis and photoluminescence properties

• Andreea Petronela Diac,
• Ana-Maria Ţepeş,
• Albert Soran,
• Ion Grosu,
• Anamaria Terec,
• Jean Roncali and
• Elena Bogdan

Beilstein J. Org. Chem. 2016, 12, 825–834, doi:10.3762/bjoc.12.81

• sciences. Besides, the annelated cyclic indenes containing N or O heteroatoms are the main structural frameworks of several natural alkaloids [1], while indenopyran derivatives were found to be valuable substrates for the synthesis of various compounds with biological activity [2][3]. Some indeno[1,2-c

Recent advances in C(sp³)–H bond functionalization via metal–carbene insertions

• Bo Wang,
• Di Qiu,
• Yan Zhang and
• Jianbo Wang

Beilstein J. Org. Chem. 2016, 12, 796–804, doi:10.3762/bjoc.12.78

• the late-stage C–H functionalization of complex alkaloids and drug molecules (Scheme 3) [25]. C–H bond insertions at the allylic and benzylic positions Metal–carbene C–H insertion is also favored for allylic and benzylic sites. In 2014, Davies and co-workers reported an enantioselective C–H insertion

Cupreines and cupreidines: an established class of bifunctional cinchona organocatalysts

• Laura A. Bryant,
• Rossana Fanelli and
• Alexander J. A. Cobb

Beilstein J. Org. Chem. 2016, 12, 429–443, doi:10.3762/bjoc.12.46

• Laura A. Bryant Rossana Fanelli Alexander J. A. Cobb School of Chemistry, Food and Pharmacy (SCFP), University of Reading, Whiteknights, Reading, Berks RG6 6AD, United Kingdom 10.3762/bjoc.12.46 Abstract Cinchona alkaloids with a free 6'-OH functionality are being increasingly used within

• . Keywords: bifunctional; cupreidine; cinchona; cupreine; organocatalysis; Introduction The cinchona alkaloids, comprising quinine (QN), quinidine (QD), cinchonidine (CD), cinchonine (CN, Figure 1), and their derivatives have revolutionized asymmetric catalysis owing to their privileged structures. The

• cinchona class of alkaloids are a dynamic and versatile type of organocatalyst that should be included in the screening libraries of chemists seeking to develop asymmetric methodologies. Review Morita–Baylis–Hillman (MBH) and MBH-carbonate reactions The first reports of an asymmetric reaction catalyzed by

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

• which provided the hydrogenated tricyclic cyclopenta[f]indole core system in high yield. Keywords: gold-catalyzed reactions; heterocycles; indole alkaloids; natural products; synthesis; Introduction The raputindoles (1, raputindole A, Figure 1) from the rutaceous tree Raputia simulans Kallunki

Exploring architectures displaying multimeric presentations of a trihydroxypiperidine iminosugar

• Camilla Matassini,
• Stefania Mirabella,
• Andrea Goti,
• Inmaculada Robina,
• Antonio J. Moreno-Vargas and
• Francesca Cardona

Beilstein J. Org. Chem. 2015, 11, 2631–2640, doi:10.3762/bjoc.11.282

• glycosidases. Keywords: dendrimers; glycosidase inhibitors; iminosugars; multivalency; piperidine alkaloids; Introduction Iminosugars are well-known naturally occurring glycomimetics with a nitrogen atom replacing the endocyclic oxygen, mainly recognized as inhibitors of carbohydrate-processing enzymes

• metabolic disorder and Helicobacter pylori infection, as well as in the elucidation of the biological role of α-L-fucosidase in spermiogenesis and sperm maturation [23]. Following our interest in the synthesis of natural alkaloids and their unnatural analogs we recently developed a straightforward synthetic

Organocatalytic and enantioselective Michael reaction between α-nitroesters and nitroalkenes. Syn/anti-selectivity control using catalysts with the same absolute backbone chirality

• Jose I. Martínez,
• Uxue Uria,
• Maria Muñiz,
• Efraím Reyes,
• Luisa Carrillo and
• Jose L. Vicario

Beilstein J. Org. Chem. 2015, 11, 2577–2583, doi:10.3762/bjoc.11.277

• advantage of the Michael addition of nitroalkenes and using two different bifunctional catalysts derived from cinchona alkaloids (catalyst 4) or cyclohexadiamine (catalyst 6). These catalysts, both with the same absolute backbone chirality, allow us to control the syn or anti selectivity obtaining the final

Bromotyrosine-derived alkaloids from the Caribbean sponge Aplysina lacunosa

• Qun Göthel,
• Thanchanok Sirirak and
• Matthias Köck

Beilstein J. Org. Chem. 2015, 11, 2334–2342, doi:10.3762/bjoc.11.254

• Qun Gothel Thanchanok Sirirak Matthias Kock Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Am Handelshafen 12, 27570 Bremerhaven, Germany 10.3762/bjoc.11.254 Abstract Three new bromotyrosine-derived alkaloids 14-debromo-11-deoxyfistularin-3 (1), aplysinin A (2), and

• of 1 and 2 were confirmed by an 1,1-ADEQUATE experiment. Compounds 1 and 2 showed a mild to moderate cytotoxic activities against KB-31 and FS4-LTM cell lines. Only aplysinin A (2) exhibited cytotoxicity against MCF-7 cells. Keywords: alkaloids; Aplysina lacunosa; bromotyrosine; marine natural

• products; NMR spectroscopy; Introduction Bromotyrosine-derived alkaloids are unique brominated metabolites which were isolated mainly from marine sponges of the order Verongida. For more than 50 years, bromotyrosine alkaloids raised the interests of synthetic and natural products chemists due to their

Beyond catalyst deactivation: cross-metathesis involving olefins containing N-heteroaromatics

• Kevin Lafaye,
• Cyril Bosset,
• Lionel Nicolas,
• Amandine Guérinot and
• Janine Cossy

Beilstein J. Org. Chem. 2015, 11, 2223–2241, doi:10.3762/bjoc.11.241

• their studies towards ergot alkaloids synthesis, Martin and co-workers used a RCM to form the tetracyclic compound 43 incorporating an indole moiety. A poor yield was obtained in the presence of the GI catalyst and the more reactive Schrock complex 44 had to be used instead. Worthy of note, the indole

The marine sponge Agelas citrina as a source of the new pyrrole–imidazole alkaloids citrinamines A–D and N-methylagelongine

• Christine Cychon,
• Ellen Lichte and
• Matthias Köck

Beilstein J. Org. Chem. 2015, 11, 2029–2037, doi:10.3762/bjoc.11.220

• alkaloids (PIAs), the citrinamines A–D (1–4) and the bromopyrrole alkaloid N-methylagelongine (5). All citrinamines are dimers of hymenidin (6) which was also isolated from this sponge as the major metabolite. Citrinamines A (1) and B (2) are derivatives of the PIA dimer mauritiamine (7), whereas

• ) which consist of a pyridinium ring and an ester linkage instead of the aminoimidazole moiety and the common amide bond in PIAs. Keywords: Agelas citrina; marine sponges; mauritiamine; NMR; pyrrole–imidazole alkaloids; Introduction The family of pyrrole-imidazole alkaloids (PIAs) represents a

• alkaloids, citrinamines C (3) and D (4), which were both obtained as mixtures. The isolation of the pure compounds of 3 and 4 by preparative chromatography failed but the analysis of the mixtures allowed the identification of their structures. The molecular weights of citrinamine C (3) (m/z 650.0493, [M + H

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

• (Scheme 6). The erythrina alkaloids are known to exhibit sedative, hypotensive and neuromuscular activity. This alkaloid skeleton consists of a tetracyclic spiroamine framework and synthetic chemists consider it as a challenging target. Simpkins and co-workers [11] have used the RRM sequence tactically to

• -1-ol (288) under optimized reaction conditions (MW, toluene, 80 °C) and the expected tandem metathesis product 289b was obtained along with the ROM–RCM product 289a. These compounds are useful synthones for the alkaloids synthesis (Scheme 61). In another instance, they also studied the efficiency of

• this method by isolating the RCM product of the ROM–CM byproduct 290, which was recovered in the ROM–RCM–CM cascade (Scheme 62). Kouklovsky and co-workers [62] have described a stereoselective synthesis of 2-(2-hydroxyalkyl)piperidine alkaloids by employing a RRM of NDA adduct 293. The required

Fe(II)/Et₃N-Relay-catalyzed domino reaction of isoxazoles with imidazolium salts in the synthesis of methyl 4-imidazolylpyrrole-2-carboxylates, its ylide and betaine derivatives

• Ekaterina E. Galenko,
• Olesya A. Tomashenko,
• Alexander F. Khlebnikov,
• Mikhail S. Novikov and
• Taras L. Panikorovskii

Beilstein J. Org. Chem. 2015, 11, 1732–1740, doi:10.3762/bjoc.11.189

• reaction with sulfur affording the corresponding imidazolethiones under very mild conditions. Keywords: imidazole; isoxazole; NHC carbene; pyrrole-2-carboxylate; relay catalysis; Introduction Pyrrole-2-carboxyate and imidazole units are present in bioactive pyrrole-imidazole alkaloids and pyrrole

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

• , confirming its antimicrobial activity. The E-configuration of the chloroalkene moiety of indiacen B was confirmed by X-ray analysis. Keywords: biological evaluation; heterocycles; indoles; natural products; total synthesis; Introduction Indole alkaloids prenylated at the benzene ring are found in tropical

• -methylbuta-1,3-dien-1-yl)indole [7]. All enamine positions of the indole units are unsubstituted. As part of our program on the total synthesis of prenylated indole alkaloids [8][9][10][11], we considered it interesting to access indoles substituted only at the benzene ring and to conduct initial studies on

• product indiacen B (2), which was synthesized for the first time, was confirmed by X-ray analysis. The antimicrobial activity of synthetic indiacen B (2) was in the same range as that originally determined for the isolated natural product. Prenylated indole alkaloids raputindole A from the rutaceous tree

Pyridinoacridine alkaloids of marine origin: NMR and MS spectral data, synthesis, biosynthesis and biological activity

• Louis P. Sandjo,
• Victor Kuete and
• Maique W. Biavatti

Beilstein J. Org. Chem. 2015, 11, 1667–1699, doi:10.3762/bjoc.11.183

• on pyridoacridine-related metabolites as one biologically interesting group of alkaloids identified from marine sources. They are produced by marine sponges, ascidians and tunicates, and they are structurally comprised of four to eight fused rings including heterocycles. Acridine, acridone

• reported, pyridoacridine 13C NMR data. Observations have been made on the delocalization of electrons and the presence of some functional groups that lead to changes in the chemical shift of some carbon resonances. The lack of mass spectra information for these alkaloids due to the compactness of their

• structures is further discussed. Moreover, the biosynthetic pathways of some of these metabolites have been shown since they could inspire biomimetic synthesis. The synthesis routes used to prepare members of these marine alkaloids (as well as their analogues), which are synthesized for biological purposes

Dicarboxylic esters: Useful tools for the biocatalyzed synthesis of hybrid compounds and polymers

• Ivan Bassanini,
• Karl Hult and
• Sergio Riva

Beilstein J. Org. Chem. 2015, 11, 1583–1595, doi:10.3762/bjoc.11.174

• ) Regioselective enzymatic acylation of natural products. Natural products are traditionally classified into groups of substances (terpenes, alkaloids, amino acids, lipids, etc), depending on their biosynthetic origin and on their chemical and structural features [19][20][21]. The complex structures of most of