A permutation approach to the assignment of the configuration to diastereomeric tetrads by comparison of experimental and ab initio calculated differences in NMR data

• Przemysław J. Boratyński

Beilstein J. Org. Chem. 2017, 13, 2478–2485, doi:10.3762/bjoc.13.245

• Cinchona alkaloids 1–4 obtained in our laboratory were analyzed (Figure 1, for references, see Supporting Information File 1). The configurations of these derivatives were established based on previous X-ray studies for compounds 2a and 3d, NOESY experiments combined with molecular modeling for compounds

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

• 29 into isocomene failed (Scheme 12) [32]. Recently, Weinreb’s group used the advantage of nitrosoalkenes as Michael acceptors to accomplish total syntheses of several alkaloids, such as (+/−)-alstilobanines A and E, (+/−)-angustilodine [33] and (+/−)-myrioneurinol [34][35] (Figure 1). In the total

• , which served as a direct precursor of target alkaloids alstilobanines A, E and angustilodine. The same strategy was employed to construct the tetracyclic core of the apparicine class of indole alkaloids (see Scheme 14) [36]. Here, coupling of indole dianion 40 with chlorooxime 35 (via nitrosoalkene NSA8

• indolactam-based alkaloids 84 (activators of protein kinase C) as shown in Scheme 30. Employing the same strategy, Webb [76] and Resnick [77] prepared analogues of teleocidin and later Quick [78] accomplished the synthesis of indolactam V. Tandem C-nucleophile addition/cyclization processes involving

Regiodivergent condensation of 5-alkoxycarbonyl-1H-pyrrol-2,3-diones with cyclic ketazinones en route to spirocyclic scaffolds

• Alexey Yu. Dubovtsev,
• Maksim V. Dmitriev,
• Аndrey N. Maslivets and
• Michael Rubin

Beilstein J. Org. Chem. 2017, 13, 2179–2185, doi:10.3762/bjoc.13.218

• in the target-oriented synthesis of pyrrole-based natural alkaloids [34][35][36][37][38]. Herein we wish to report a new synthetic route towards spirocyclic scaffolds possessing partially hydrogenated indole or benzofuran cores. The featured approach is based on the highly efficient regiodivergent

Accessing simply-substituted 4-hydroxytetrahydroisoquinolines via Pomeranz–Fritsch–Bobbitt reaction with non-activated and moderately-activated systems

• Marco Mottinelli,
• Mathew P. Leese and
• Barry V. L. Potter

Beilstein J. Org. Chem. 2017, 13, 1871–1878, doi:10.3762/bjoc.13.182

• , Oxford, OX1 3QT, UK 10.3762/bjoc.13.182 Abstract Background: 1,2,3,4-Tetrahydroisoquinolines (THIQs) are common motifs in alkaloids and in medicinal chemistry. Synthetic access to THIQs via the Pomeranz–Fritsch–Bobbit (PFB) methodology using mineral acids for deactivated, electron-poor aromatic systems

• ; steroidomimetic; synthesis; tetrahydroisoquinoline; Introduction 1,2,3,4-Tetrahydroisoquinoline (THIQ) motifs are present in many natural alkaloids [1]. THIQ derivatives have also been investigated as potential therapeutics in a wide range of diseases and recent studies have explored their potential as

Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

• Johannes Schörgenhumer,
• Maximilian Tiffner and
• Mario Waser

Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170

• , cinchona alkaloids remained the preferred chiral backbones for novel phase-transfer catalysts and applications thereof until the beginning of the 21st century. Pioneering contributions with these powerful catalysts were reported by the groups of O’Donnell [27], Lygo [28], and Corey [29]. The turn of the

• cinchona-based PTCs A for such α-fluorination reactions was reported in 2013 by the groups of Meng and Lu [76]. By screening a variety of differently modified ammonium salts A, they found that the introduction of sterically demanding 1-adamantoyl esters in the 9-position of the cinchona alkaloids in

• alkaloid-based organocatalysts to carry out the α-trifluoromethylthiolation of β-ketoesters 1 by using the hypervalent iodine-based CF3S-transfer reagent 36 in an asymmetric fashion. Very interestingly, they realized that for indanone-based ketoesters 1 (with n = 1) simple cinchona alkaloids themselves

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

• Santanu Hati,
• Ulrike Holzgrabe and
• Subhabrata Sen

Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162

• alkaloids such as luotonin A, tryptanthrin and many more (Figure 1) [11][12]. Quinazoline derivatives work as potential inhibitors of epidermal growth factor (EGF) and tyrosine kinase receptors and also display antibacterial, antitubercular and antiviral properties [13][14][15][16]. Last but not the least

A novel approach to oxoisoaporphine alkaloids via regioselective metalation of alkoxy isoquinolines

• Benedikt C. Melzer and
• Franz Bracher

Beilstein J. Org. Chem. 2017, 13, 1564–1571, doi:10.3762/bjoc.13.156

• Benedikt C. Melzer Franz Bracher Department für Pharmazie - Zentrum für Pharmaforschung, Ludwig-Maximilians Universität München, Butenandtstr. 5-13, D-81377 Munich, Germany 10.3762/bjoc.13.156 Abstract Oxoisoaporphine alkaloids are conveniently prepared via direct ring metalation of alkoxy

• -substituted isoquinolines at C-1, followed by reaction with iodine. Subsequent Suzuki cross-coupling of the resulting 1-iodoisoquinolines to methyl 2-(isoquinolin-1-yl)benzoates and intramolecular acylation of the corresponding carboxylic acids with Eaton’s reagent afforded five alkaloids of the

• oxoisoaporphine type. The yield of the cyclization step strongly depends on the electrophilic properties of ring B. An alternative cyclization protocol via directed remote metalation of ester and amide intermediates was investigated thoroughly, but found to be not feasible. Two of the alkaloids showed strong

Bifunctional organocatalysts for the asymmetric synthesis of axially chiral benzamides

• Ryota Miyaji,
• Yuuki Wada,
• Akira Matsumoto,
• Keisuke Asano and
• Seijiro Matsubara

Beilstein J. Org. Chem. 2017, 13, 1518–1523, doi:10.3762/bjoc.13.151

• solvent (Table 1, entries 4–7). Other brominating reagents (Figure 1) were also investigated; however, NBA (4a) still afforded the best enantioselective results (Table 1, entries 8–10). In addition, other bifunctional organocatalysts derived from easily available cinchona alkaloids exhibited similarly

A speedy route to sterically encumbered, benzene-fused derivatives of privileged, naturally occurring hexahydropyrrolo[1,2-b]isoquinoline

• Olga Bakulina,
• Alexander Ivanov,
• Vitalii Suslonov,
• Dmitry Dar’in and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2017, 13, 1413–1424, doi:10.3762/bjoc.13.138

• deliver hexahydropyrrolo[1,2-b]isoquinolones 4. The hexahydropyrrolo[1,2-b]isoquinoline core in general is ubiquitous to many natural products exemplified by tylophorine (5) [18], lycorine (6) [19] and its entire family of alkaloids, including zephyranthine (7) [20] and galantine (8) [21]. Considering the

• plethora of biological activities displayed by the lycorine and tylophorine alkaloids (such as pro-apoptotic [22], antiviral [23], hypoxia-inducible factor-1 inhibitory [24]), the scaffold can be confidently regarded as privileged [25]. Recently, we [26] and others [27] reported the use of indolenines as

Characterization of non-heme iron aliphatic halogenase WelO5* from Hapalosiphon welwitschii IC-52-3: Identification of a minimal protein sequence motif that confers enzymatic chlorination specificity in the biosynthesis of welwitindolelinones

• Qin Zhu and
• Xinyu Liu

Beilstein J. Org. Chem. 2017, 13, 1168–1173, doi:10.3762/bjoc.13.115

• molecules. Although the initially characterized WelO5 has a restricted substrate scope [17], we have recently shown its homolog, AmbO5, in the biogenesis of ambiguines is capable of modifying seven structurally distinct hapalindole-type alkaloids [18]. The biochemical characterizations of WelO5/AmbO5

• basis for the altered structural diversity of hapalindole-type alkaloids between the two welwitindolinone producers. The extreme sequence similarity (95% identical) between WelO5* and WelO5 allowed us to trace the origin of this observed specificity difference to 11 amino acid residues at a C-terminal

• application. Results and Discussion H. welwitschii IC-52-3 and UTEX B1830 are two known welwitindolinone producers that were reported to produce identical sets of hapalindole-type alkaloids [20], albeit the detailed metabolite analysis from the latter was never published. During our recent effort to define

A strategic approach to [6,6]-bicyclic lactones: application towards the CD fragment of DHβE

• Tue Heesgaard Jepsen,
• Emil Glibstrup,
• François Crestey,
• Anders A. Jensen and
• Jesper Langgaard Kristensen

Beilstein J. Org. Chem. 2017, 13, 988–994, doi:10.3762/bjoc.13.98

• tetracyclic Erythrina alkaloids which were isolated from Erythrina species in the end of the 19th century; the majority of this family possesses neuromuscular blocking effects [2]. DHβE is one of the most potent nAChR antagonists of this class and displays prominent selectivity for the α4β2 subtype (Ki = 0.82

• CD fragment of DHβE. Previously, the aromatic CD fragments were straightforwardly synthesized due to the advantageous reactivity of the aromatic D ring [10]. However, the syntheses of the lactonic Erythrina alkaloids are more complex [11][12] as illustrated by more than 150 total syntheses reported

A practical and efficient approach to imidazo[1,2-a]pyridine-fused isoquinolines through the post-GBB transformation strategy

• Taofeng Shao,
• Zhiming Gong,
• Tianyi Su,
• Wei Hao and
• Chao Che

Beilstein J. Org. Chem. 2017, 13, 817–824, doi:10.3762/bjoc.13.82

• (Figure 1) [6]. Furthermore, the isoquinoline motif represents a privileged medicinal skeleton widely found in a number of natural alkaloids and pharmaceutically active compounds [7]. Some of them exhibit diversified biological properties, including anti-inflammatory [8], antibacterial [9], antiviral [10

• ], and antitumor activities [11]. For example, the natural alkaloids berberine (IV) and narciclasine (V) possess antiplasmodial and antiviral activity, respectively [12][13]. Indotecan (VI) and its analog idimitecan (VII) were identified as topoisomerase I inhibitors, and were promoted into phase I

• to structurally complex polycyclic ring systems [33]; an Ugi/aza-Wittig process allowed for the synthesis of 2,5-disubstituted 1,3,4-oxadiazoles [34]; the Ugi/Pictet–Spengler sequence provided a rapid and efficient approach to polycyclic natural product-like alkaloids [35]. Accordingly, the

Exploring endoperoxides as a new entry for the synthesis of branched azasugars

• Svenja Domeyer,
• Mark Bjerregaard,
• Henrik Johansson and
• Daniel Sejer Pedersen

Beilstein J. Org. Chem. 2017, 13, 644–647, doi:10.3762/bjoc.13.63

• hydrolysis transition states as well as having many other interesting properties. They are found in nature as pyrrolidines, piperidines, indolizidines, pyrrolizidines or nortropane alkaloids with a variety of ring substituents, typically hydroxy groups, carboxylic acids and amides [1]. The ability of

Biosynthetic origin of butyrolactol A, an antifungal polyketide produced by a marine-derived Streptomyces

• Enjuro Harunari,
• Hisayuki Komaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2017, 13, 441–450, doi:10.3762/bjoc.13.47

• diverse secondary metabolites with pharmaceutically useful bioactivities. Importantly, members of the genus Streptomyces have been the main source of drug discovery programs due to their high capacity in secondary metabolism including polyketides, peptides, terpenoids, alkaloids, and amino acid

Brønsted acid-mediated cyclization–dehydrosulfonylation/reduction sequences: An easy access to pyrazinoisoquinolines and pyridopyrazines

• Ramana Sreenivasa Rao and
• Chinnasamy Ramaraj Ramanathan

Beilstein J. Org. Chem. 2017, 13, 428–440, doi:10.3762/bjoc.13.46

• for the synthesis of many alkaloids (Figure 1) [16]. To synthesize pyrazinoisoquinoline and its derivatives, various approaches such as the Ugi multicomponent reaction [17] amidoalkylation [18][19], N-acyliminium ion cyclization [20] and a radical cyclization [21] have been reported. To this end

• , recently, we have reported the activation of an imide carbonyl group with TfOH, for the synthesis of tetrahydroisoquinoline (THIQ) and tetrahydro-β-carboline (THBC) skeletons and related alkaloids [22][23][24][25][26]. The present study, describes the synthesis of 4-benzenesulfonylpiperazine-2,6-dione

Posttranslational isoprenylation of tryptophan in bacteria

• Masahiro Okada,
• Tomotoshi Sugita and
• Ikuro Abe

Beilstein J. Org. Chem. 2017, 13, 338–346, doi:10.3762/bjoc.13.37

• . ComQ lacks homology to cysteine isoprenyltransferases, tryptophan dimethylallyltransferases for cyanobactins [2][37][38] or prenyltransferases for indole alkaloids [39][40][41][42]. However, ComQ shares some homology with farnesyl diphosphate (FPP) synthases and geranylgeranyl diphosphate (GGPP

• ABBA fold and exhibits some similarity to other dimethylallyltransferases for cyanobactins and prenyltransferases for indole alkaloids, but lacks similarity to cysteine isoprenyltransferases and ComQs [2][37][38][39][40][41][42][43][44]. Considering the in vitro prenylation analysis of KgpF together

The reductive decyanation reaction: an overview and recent developments

• Jean-Marc R. Mattalia

Beilstein J. Org. Chem. 2017, 13, 267–284, doi:10.3762/bjoc.13.30

• ]. Opatz et al. developed the enantioselective syntheses of various alkaloids using the rhodium catalyst developed by Noyori [88] for the asymmetric transfer hydrogenation of imines. Interestingly, imines are formed from unstable α-aminonitrile intermediates which spontaneously eliminate HCN [89][90][91

Interactions between photoacidic 3-hydroxynaphtho[1,2-b]quinolizinium and cucurbit[7]uril: Influence on acidity in the ground and excited state

• Jonas Becher,
• Daria V. Berdnikova,
• Darinka Dzubiel,
• Heiko Ihmels and
• Phil M. Pithan

Beilstein J. Org. Chem. 2017, 13, 203–212, doi:10.3762/bjoc.13.23

• charge providing ion–dipole interactions with the carbonyl portals of CB[7] as well as its extended π system, that was proposed to cause a higher affinity to the CB[7] due to an increased hydrophobic effect. Moreover, the naphthoquinolizinium ion resembles the quinolizinium-type alkaloids palmatine

• that can thread nicely into the binding site. Notably, the structurally resembling alkaloids berberine (8a) and palmatine (8b), that contain an angularly annelated quinolizinium unit, also bind to CB[7]. But whereas palmatine (8b) has essentially the same binding constant as 2 (Kb = 4.3 × 104 M−1, in

Synthesis of structurally diverse 3,4-dihydropyrimidin-2(1H)-ones via sequential Biginelli and Passerini reactions

• Andreas C. Boukis,
• Baptiste Monney and
• Michael A. R. Meier

Beilstein J. Org. Chem. 2017, 13, 54–62, doi:10.3762/bjoc.13.7

• modulation, α1a adrenoceptor-selective antagonists, cancer therapy, anti-HIV alkaloids) [12][13][14][15]. The mechanism of the Biginelli cyclocondensation was proposed and investigated by Kappe and is illustrated in Scheme 1a [16]. According to the generally accepted mechanism of the Biginelli reaction

Multicomponent synthesis of spiropyrrolidine analogues derived from vinylindole/indazole by a 1,3-dipolar cycloaddition reaction

• Manjunatha Narayanarao,
• Lokesh Koodlur,
• Vijayakumar G. Revanasiddappa,
• Subramanya Gopal and
• Susmita Kamila

Beilstein J. Org. Chem. 2016, 12, 2893–2897, doi:10.3762/bjoc.12.288

• [7][8][9][10]. Indole and indazolyl subunits are central to numerous alkaloids and are constituents of many classes of compounds that display a wide range of bioactivities such as antimycobacterial, anti-inflammatory, antihypertensive, anticancer, antidepressant, antidiabetic, antimalarial

Synthesis of spiro[isoindole-1,5’-isoxazolidin]-3(2H)-ones as potential inhibitors of the MDM2-p53 interaction

• Salvatore V. Giofrè,
• Santa Cirmi,
• Raffaella Mancuso,
• Francesco Nicolò,
• Giuseppe Lanza,
• Laura Legnani,
• Agata Campisi,
• Maria A. Chiacchio,
• Michele Navarra,
• Bartolo Gabriele and
• Roberto Romeo

Beilstein J. Org. Chem. 2016, 12, 2793–2807, doi:10.3762/bjoc.12.278

• example MI-63 and MI-219, [15][16][17][18] have demonstrated cellular activity consistent with inhibition of MDM2-p53 binding and have shown in vivo antitumor activity [15][19] (Figure 1). Isoindolinones, belonging to the alkaloids family, are found in many natural products such as vitedoamine A

New syntheses of (±)-tashiromine and (±)-epitashiromine via enaminone intermediates

• Darren L. Riley,
• Joseph P. Michael and
• Charles B. de Koning

Beilstein J. Org. Chem. 2016, 12, 2609–2613, doi:10.3762/bjoc.12.256

• piperidine or a pyrrolidine-based precursor, with few reports of alternative approaches. The approach adopted by our research group to the synthesis of these and related bicyclic alkaloids takes advantage of enaminone chemistry [10][11][12][13][14][15][16][17][18][19]. Our interest in the enaminone manifold

• stems mainly from its ability to display both ambident nucleophilic and electrophilic reactivity, properties that have frequently been exploited in the synthesis of alkaloids and other nitrogen-containing heterocycles [20][21][22][23]. The enaminone and related units that form the basis of our own

Biomimetic synthesis and HPLC–ECD analysis of the isomers of dracocephins A and B

• Viktor Ilkei,
• András Spaits,
• Anita Prechl,
• Áron Szigetvári,
• Zoltán Béni,
• Miklós Dékány,
• Csaba Szántay Jr,
• Judit Müller,
• Árpád Könczöl,
• Ádám Szappanos,
• Attila Mándi,
• Sándor Antus,
• Ana Martins,
• Attila Hunyadi,
• György Tibor Balogh,
• György Kalaus (†),
• Hedvig Bölcskei,
• László Hazai and
• Tibor Kurtán

Beilstein J. Org. Chem. 2016, 12, 2523–2534, doi:10.3762/bjoc.12.247

• and TDDFT–ECD calculations. The synthesized flavonoid alkaloids were further characterized by physicochemical and in vitro pharmacological studies. Keywords: absolute configuration; Dracocephalum rupestre; dracocephins A–B; ECD calculation; flavonoid alkaloids; HPLC–ECD; Introduction Flavonoid

• alkaloids are a small subgroup of flavonoids possessing a five- or six-membered nitrogen heterocycle attached to C-6 or C-8 of ring A of the flavonoid moiety. They have been reported to exhibit a wide range of pharmacological activities [1]. Dracocephins A and B were isolated as a mixture of four

• cyclization of the Strecker aldehyde 5 yields the acylaminocarbinol intermediate 6, which readily loses water on protonation, resulting in the N-acyliminium ion 7a/b, a strong electrophilic reagent. Results and Discussion The aim of our work was to synthesize the natural flavonoid alkaloids 2a–d and 3a–d in a

Facile synthesis of indolo[3,2-a]carbazoles via Pd-catalyzed twofold oxidative cyclization

• Chao Yang,
• Kai Lin,
• Lan Huang,
• Wei-dong Pan and
• Sheng Liu

Beilstein J. Org. Chem. 2016, 12, 2490–2494, doi:10.3762/bjoc.12.243

• materials. The operational simplicity combined with the convenience for introducing substituents to the aromatic rings makes this method useful. Natural indolo[3,2-a]carbazole alkaloids. Retrosynthetic analysis of indolo[3,2-a]carbazoles. Reagents and conditions: (a) H2SO4, MeOH; (b) Ar-NH2, Pd(OAc)2, BINAP

Experimental and theoretical investigations into the stability of cyclic aminals

• Edgar Sawatzky,
• Antonios Drakopoulos,
• Martin Rölz,
• Christoph Sotriffer,
• Bernd Engels and
• Michael Decker

Beilstein J. Org. Chem. 2016, 12, 2280–2292, doi:10.3762/bjoc.12.221

• ; Introduction The aminal system (N,N-acetal) is the structurally equivalent analogue of the O,O-acetal. In the literature this moiety is found as a core element in various important structures, for example in the naturally occurring alkaloids tetraponerine T1 to T8 from the venom of the New Guinean ant

• with KMnO4 or a mixture of potassium iodide and tert-butyl hydroperoxide (TBHP) give access to quinazolinones and have been reported for the synthesis of the naturally occurring alkaloids deoxyvasicinone, mackinazolinone or rutaecarpine [22][28] (Scheme 2). Besides total oxidation of the aminal core

• , also a partial oxidation towards 3,4-dihydroquinazolines is possible for the case that the oxidation is promoted either by Cu(AcO)2 or by a mixture of elemental iodine and BuLi. These methods allow the synthesis of the partially unsaturated alkaloids vasicine or deoxyvasicine in good yields [22][28