Asymmetric Michael addition reactions catalyzed by calix[4]thiourea cyclohexanediamine derivatives

• Zheng-Yi Li,
• Hong-Xiao Tong,
• Yuan Chen,
• Hong-Kui Su,
• Tangxin Xiao,
• Xiao-Qiang Sun and
• Leyong Wang

Beilstein J. Org. Chem. 2018, 14, 1901–1907, doi:10.3762/bjoc.14.164

• ]. In 2016, Hernández-Rodríguez and co-workers reported the preparation of bifunctional thioureas that contained either a methyl or trifluoromethyl group [14]. They discovered that the employment of chiral moieties with an α-trifluoromethyl group in thioureas show a positive effect on the selectivity

• of ortho- or para-halogenated substrates. Mechanism study There are two possibilities for the bifunctional thiourea-catalyzed asymmetric Michael addition reaction mechanism as has been summarized by Wang and co-worker [41]. In case of 1,3-dicarbonyl compounds or nitroolefins as substrates in the

Drug targeting to decrease cardiotoxicity – determination of the cytotoxic effect of GnRH-based conjugates containing doxorubicin, daunorubicin and methotrexate on human cardiomyocytes and endothelial cells

• Livia Polgár,
• Eszter Lajkó,
• Pál Soós,
• Orsolya Láng,
• Marilena Manea,
• Béla Merkely,
• Gábor Mező and
• László Kőhidai

Beilstein J. Org. Chem. 2018, 14, 1583–1594, doi:10.3762/bjoc.14.136

• Supporting Information File 1. Chemical structures of the GnRH-drug conjugates synthesized and investigated in the present work. Abbreviations: Aoa: aminooxyacetyl; Dox: doxorubicin; Dau: daunorubicin; Mtx: methotrexate; Glp: pyroglutamic acid; gult: glutaric acid. Chemical structures of the bifunctional

• bifunctional daunorubicin-GnRH-III conjugates without spacer and modified in position 4 with Lys; (e) {GnRH-III(Dau=Aoa-C)}2 dimer and conjugates modified in position 4 with N-MeSer; (f) GFLG or YRRL spacer containing monomer and dimer conjugates (g) GnRH-III conjugates containing methotrexate and daunorubicin

• conjugates containing doxorubicin without spacer sequence; (c) with spacer sequence GFLG; (d) oxime bond-linked, mono- and bifunctional daunorubicin-GnRH-III conjugates without spacer and modified in position 4 with Lys; (e) {GnRH-III(Dau=Aoa-C)}2 dimer and conjugates modified in position 4 with N-MeSer; (f

Cobalt–metalloid alloys for electrochemical oxidation of 5-hydroxymethylfurfural as an alternative anode reaction in lieu of oxygen evolution during water splitting

• Jonas Weidner,
• Stefan Barwe,
• Kirill Sliozberg,
• Stefan Piontek,
• Justus Masa,
• Ulf-Peter Apfel and
• Wolfgang Schuhmann

Beilstein J. Org. Chem. 2018, 14, 1436–1445, doi:10.3762/bjoc.14.121

• [4]. The elaborate separation of TEMPO from FDCA appeared to be an additional disadvantage [24]. Recently, Sun and co-workers reported the electrochemical oxidation of HMF using various non-precious cobalt and nickel based bifunctional HER/OER water splitting electrocatalysts, namely CoP on copper

• foam, Ni2P and Ni3S2 on nickel foam, in a one compartment batch type electrochemical reactor [5][28][29]. We recently reported on the synthesis and application of alloys of cobalt with boron and phosphorus as exceptionally active bifunctional HER/OER catalysts for water splitting. Inspired by these

Recent applications of chiral calixarenes in asymmetric catalysis

• Mustafa Durmaz,
• Erkan Halay and
• Selahattin Bozkurt

Beilstein J. Org. Chem. 2018, 14, 1389–1412, doi:10.3762/bjoc.14.117

• asymmetric synthesis. In 2013, we described a novel class of calix[4]arene-based chiral primary amine–thiourea catalysts 47a and 47b derived from p-tert-butylcalix[4]arene (Figure 7) [49]. To evaluate the catalytic efficiency, bifunctional catalysts were applied to promote the Michael addition of aldehydes

• -diaminocyclohexane moiety from (1R,2R) to (1S,2S) without loss of activity or selectivity. Bifunctional organic molecules combining the thiourea moiety with a tertiary amine functionality are remarkably useful catalysts capable of simultaneous activation of both electrophiles and nucleophiles [51]. Therefore, a

• series of calixarene-based chiral bifunctional tertiary amine–thiourea organocatalysts 54–56 have been synthesized by us and Genc et al. (Scheme 15) [52][53]. Among them, 54a,b were applied to the asymmetric Michael addition of 1,3-dicarbonyl compounds 34 and 57 to a variety of nitroolefins. Although

Synthesis of chiral 3-substituted 3-amino-2-oxindoles through enantioselective catalytic nucleophilic additions to isatin imines

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 1349–1369, doi:10.3762/bjoc.14.114

• -isatin imines 3 with naphthols performed in the presence of cinchona alkaloid-derived thiourea 40 [66]. As shown in Scheme 15, the reaction of 1-naphthols 42 promoted by 2 mol % of this bifunctional catalyst in toluene at room temperature led to the corresponding chiral 3-substituted 3-amino-2-oxindoles

• either chiral organocatalysts or chiral metal complexes. Among the organocatalysts, chiral bifunctional guanidine 50 was applied by Feng et al. in 2015 to promote the reaction of nitromethane 51 with N-Boc-isatin imines 3 (Scheme 18) [71]. The reaction performed at −30 °C using 10 mol % of this catalyst

• reactions performed with bifunctional guanidines. In addition, excellent results (97% ee) were reported in unprecedented domino reactions promoted by squaramides recently. Miscellaneous transformations, including additions of methanol, hydroperoxides and arylboronic acids, were also developed with high

Volatiles from three genome sequenced fungi from the genus Aspergillus

• Jeroen S. Dickschat,
• Ersin Celik and
• Nelson L. Brock

Beilstein J. Org. Chem. 2018, 14, 900–910, doi:10.3762/bjoc.14.77

• ). A phylogenetic analysis of 878 fungal terpene synthase homologs (Figure S1 in Supporting Information File 1) demonstrates that this enzyme is closely related to the bifunctional ent-copalyl diphosphate synthase/ent-kaurene synthase from Fusarium fujikuroi [33]. The N-terminal domain shows the DXDD

• TS homologs (accession numbers GAA83682, GAA88217 and GAA91251, locus tags AKAW_01797, AKAW_06331 and AKAW_09365). The first enzyme GAA83682 shows close homology to the bifunctional ent-kaurene synthases from Fusarium and is likely involved in diterpene biosynthesis. The fact that no corresponding

• enzyme XP_001276070 (ACLA_076850), likely a bifunctional diterpene synthase (DTS), seems to be not expressed in laboratory culture, but another function cannot be excluded for this enzyme. Esters were the predominant class of compounds emitted by A. clavatus. The observed pattern of volatiles was very

Phosphodiester models for cleavage of nucleic acids

• Satu Mikkola,
• Tuomas Lönnberg and
• Harri Lönnberg

Beilstein J. Org. Chem. 2018, 14, 803–837, doi:10.3762/bjoc.14.68

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• -2-naphthols [81]. These bifunctional compounds were reacted with various cyclic imines such as 4,5-dihydrobenzo[c]azepine or 6,7-dihydrothieno[3,2-c]pyridine to have new naphthoxazinobenzazepine 44 and -thienopyridine 45 derivatives [82]. Transformations at 80 °C in 1,4-dioxane as solvent were

• indication that the application of this highly-reactive intermediate has made the modified Mannich reaction to be a hot topic again in organic chemistry. This review presents a wide range of applications including cycloadditions and the synthesis of bifunctional amino- or amidonaphthols that can later be

Investigations towards the stereoselective organocatalyzed Michael addition of dimethyl malonate to a racemic nitroalkene: possible route to the 4-methylpregabalin core structure

• Denisa Vargová,
• Rastislav Baran and
• Radovan Šebesta

Beilstein J. Org. Chem. 2018, 14, 553–559, doi:10.3762/bjoc.14.42

• and pregabalin [9][10]. Later, hydrogen-bonding activation proved to be more general for obtaining Michael adducts via the addition of 1,3-dicarbonyl compounds to nitroalkenes. Chiral thioureas and squaramides, particularly those with the bifunctional mode of action, served as excellent catalysts in

Carbohydrate inhibitors of cholera toxin

• Vajinder Kumar and
• W. Bruce Turnbull

Beilstein J. Org. Chem. 2018, 14, 484–498, doi:10.3762/bjoc.14.34

• [70][71]. For example, using a fragment-based approach, Tran et al. synthesised and evaluated a library of polymer-based hetero-bifunctional ligands and found that some compounds showed low nanomolar multivalent inhibition [68]. Alpha-galactoside 38 (Figure 17) showed the highest activity when

• -bifunctional inhibitor designed by Bundle and co-workers. Glycopolymers with exchangeable sugar ligands and variable length linkers. Acknowledgements This review is part of a project that has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska

Stimuli-responsive oligonucleotides in prodrug-based approaches for gene silencing

• Françoise Debart,
• Christelle Dupouy and
• Jean-Jacques Vasseur

Beilstein J. Org. Chem. 2018, 14, 436–469, doi:10.3762/bjoc.14.32

Synthesis and biological evaluation of RGD and isoDGR peptidomimetic-α-amanitin conjugates for tumor-targeting

• Lizeth Bodero,
• Paula López Rivas,
• Barbara Korsak,
• Torsten Hechler,
• Andreas Pahl,
• Christoph Müller,
• Daniela Arosio,
• Luca Pignataro,
• Cesare Gennari and
• Umberto Piarulli

Beilstein J. Org. Chem. 2018, 14, 407–415, doi:10.3762/bjoc.14.29

• synthetic peptides or peptidomimetics containing these sequences have been prepared and show low nanomolar IC50 values for integrin αVβ3 binding [21][22][23][24][25][26][27]. A number of cyclic RGD and isoDGR ligands containing a bifunctional diketopiperazine (DKP) scaffold have been developed by the

Novel amide-functionalized chloramphenicol base bifunctional organocatalysts for enantioselective alcoholysis of meso-cyclic anhydrides

• Lingjun Xu,
• Shuwen Han,
• Linjie Yan,
• Haifeng Wang,
• Haihui Peng and
• Fener Chen

Beilstein J. Org. Chem. 2018, 14, 309–317, doi:10.3762/bjoc.14.19

• )-GABOB. Keywords: alcoholysis desymmetrization; bifunctional organocatalysis; chloramphenicol base; Introduction Over the past decade, remarkable advances in the utilization of natural products as chiral structural motifs for the design of bifunctional organocatalysts have been achieved. A high

• development of chiral bifunctional urea 1 [35], thiourea 2 and 3 [36][37], sulfonamide 4 [38][39][40] and squaramide 5 [38][39][40] catalysts derived from chloramphenicol base (Figure 1), which showed excellent reactivity and enantioselectivity for this asymmetric transformation. A typical example of the

• -derived bifunctional derivatives catalyzed asymmetric alcoholysis of anhydride, the exploration of new effective and easily accessible fully synthetic organocatalysts through further modification of this privilege motif are always needed. Our present design is inspired by cinchona-derived sulfonamides

Vinylphosphonium and 2-aminovinylphosphonium salts – preparation and applications in organic synthesis

• Anna Kuźnik,
• Roman Mazurkiewicz and
• Beata Fryczkowska

Beilstein J. Org. Chem. 2017, 13, 2710–2738, doi:10.3762/bjoc.13.269

• vinylphosphonium salts are important reagents and building blocks in organic synthesis mainly due to the convenience of their transformation into reactive ylides by addition of a variety of nucleophiles, including carbon, nitrogen, sulfur, and oxygen nucleophiles. The addition of a bifunctional nucleophile with a

Pyrene–nucleobase conjugates: synthesis, oligonucleotide binding and confocal bioimaging studies

• Artur Jabłoński,
• Yannic Fritz,
• Hans-Achim Wagenknecht,
• Rafał Czerwieniec,
• Tytus Bernaś,
• Damian Trzybiński,
• Krzysztof Woźniak and
• Konrad Kowalski

Beilstein J. Org. Chem. 2017, 13, 2521–2534, doi:10.3762/bjoc.13.249

• synthesis, DFT calculations, photophysical characterization, oligonucleotide binding studies, and confocal microscopy studies of the novel pyrene–nucleobase conjugates 2–5 (nucleobase = thymine (2 and 4), and adenine (3 and 5)). Our compounds represent a simple bifunctional design combining the fluorescent

Preactivation-based chemoselective glycosylations: A powerful strategy for oligosaccharide assembly

• Weizhun Yang,
• Bo Yang,
• Sherif Ramadan and
• Xuefei Huang

Beilstein J. Org. Chem. 2017, 13, 2094–2114, doi:10.3762/bjoc.13.207

• disaccharide 7, which could be subjected to bromine-promoted glycosylation for further chain elongation. As an example, preactivation of a monosaccharide 8 with bromine was followed by the addition of a bifunctional disaccharide building block 10 and subsequent TMSOTf-promoted orthoester rearrangement

• thioglycosyl building blocks as illustrated in Scheme 9 [38]. The hemiacetal donor 38 was preactivated with Ph2SO and Tf2O, and reacted with a bifunctional thioglycosyl acceptor 39 to form disaccharide 40. Interestingly, thioglycoside 40 could also be activated by Ph2SO/Tf2O. The subsequent addition of

• mixed together with a bifunctional thioglycosyl acceptor with lower anomeric reactivity (Scheme 12). Upon the addition of a promoter, the donor is preferentially activated to glycosylate the acceptor. The resulting disaccharide can then be utilized directly as a donor to react with another bifunctional

New bio-nanocomposites based on iron oxides and polysaccharides applied to oxidation and alkylation reactions

• Daily Rodríguez-Padrón,
• Alina M. Balu,
• Antonio A. Romero and
• Rafael Luque

Beilstein J. Org. Chem. 2017, 13, 1982–1993, doi:10.3762/bjoc.13.194

• on iron oxide and the polysaccharide S4, obtained from Lentinus Tigrinus (PS4). The most promising feature of such nanoentities based on iron oxide and polysaccharides is the bifunctional, oxidative [20] and acidic nature [21], which in turn can be fine-tuned to design highly active materials for

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

• asymmetric applications. Besides quaternary ammonium salts, also chiral phosphonium salts [21][36], chiral (bis)guanidinium systems [22][27][37], chiral crown ethers [38][39], bifunctional onium salts [17][40][41][42][43][44][45][46], or even sulfonium salts [47][48] have been systematically developed very

• combination with an anthracenylmethyl quaternary ammonium group (resulting in catalyst A2) allows them to carry out the syntheses of products 3 with high enantioselectivities [76]. Our group has over the last years been interested in the design and development of bifunctional (thio)urea/ammonium salt

• synthesis of differently substituted ketoesters 3 with good to high enantioselectivities by using just 2 mol % of the bifunctional catalyst. Very interestingly, Shi’s group very recently also reported PEG-bound derivatives of these catalysts which performed more or less equally selective for this

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

• Ryota Miyaji Yuuki Wada Akira Matsumoto Keisuke Asano Seijiro Matsubara Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Kyotodaigaku-Katsura, Nishikyo, Kyoto 615-8510, Japan 10.3762/bjoc.13.151 Abstract Bifunctional organocatalysts bearing amino and urea

• functional groups in a chiral molecular skeleton were applied to the enantioselective synthesis of axially chiral benzamides via aromatic electrophilic bromination. The results demonstrate the versatility of bifunctional organocatalysts for the enantioselective construction of axially chiral compounds

• . Moderate to good enantioselectivities were afforded with a range of benzamide substrates. Mechanistic investigations were also carried out. Keywords: axial chirality; benzamide; bifunctional organocatalyst; molecular conformation; multipoint recognition; Introduction Bifunctional organocatalysts have

Construction of highly enantioenriched spirocyclopentaneoxindoles containing four consecutive stereocenters via thiourea-catalyzed asymmetric Michael–Henry cascade reactions

• Yonglei Du,
• Jian Li,
• Kerong Chen,
• Chenglin Wu,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2017, 13, 1342–1349, doi:10.3762/bjoc.13.131

• asymmetric catalytic synthesis of saturated spirocyclopentaneoxindoles containing four consecutive stereocenters with 3-substituted oxindoles and nitrovinylacetamide using a bifunctional thiourea catalyst in good yields (up to 95%) with excellent diastereoselectivity (up to 3:97) and enantioselectivity (up

• , respectively (Table 1, entries 1 and 2). Further experiments showed that a bifunctional thiourea catalyst d was the most efficient for the synthesis of spirocyclic oxindole derivatives in good yields (80%) with excellent diastereoselectivity (8:92 dr), and moderate enantioselectivity (83% ee, Table 1, entries

One-pot synthesis of block-copolyrotaxanes through controlled rotaxa-polymerization

• Jessica Hilschmann,
• Gerhard Wenz and
• Gergely Kali

Beilstein J. Org. Chem. 2017, 13, 1310–1315, doi:10.3762/bjoc.13.127

• acrylate and an acrylamide in the presence of methylated β-cyclodextrin was employed for the first time to synthesize block-copolyrotaxanes. RAFT polymerizations started from a symmetrical bifunctional trithiocarbonate and gave rise to triblock-copolymers where the outer polyacrylate/polyacrylamide blocks

• other polymerization techniques, such as atom transfer radical polymerization, because of the lack of toxic metal additives, and because of good control exerted in aqueous solution. The water-soluble bifunctional CTA S,S′-bis(α,α′-dimethyl-α′′-acetic acid)trithiocarbonate (DMATC) was selected because it

• polymerization, we investigated the synthesis of ABA triblock-copolyrotaxanes from the same building blocks in a two-step process as displayed in Scheme 2. First, one of the stopper monomers was homopolymerized by RAFT process starting from the bifunctional CTA, DMATC. In the second step, isoprene, complexed in

Opportunities and challenges for the sustainable production of structurally complex diterpenoids in recombinant microbial systems

• Katarina Kemper,
• Max Hirte,
• Markus Reinbold,
• Monika Fuchs and
• Thomas Brück

Beilstein J. Org. Chem. 2017, 13, 845–854, doi:10.3762/bjoc.13.85

• example in the biosynthesis of labdane- and clerodane type diterpenes [41]. This close collaboration is performed either in one single bifunctional enzyme containing structure motifs of both types or sets of two different monofunctional synthases of both classes [54][55]. Engineering measures can directly

• performed in vivo substrate promiscuity tests following a combinatorial approach [41][66]. The resulting products entailed pimarane- and abietane-type diterpenes as well as the trans-clerodane type diterpene kolavenol, a putative intermediate in the salvinorin A biosynthesis. Other bifunctional diterpene

• example of these bifunctional enzymes was published by Chen and coworkers [60], who managed to crystalize catalytic domains of PaFS, a diterpene synthase from Phomopsis amygdali. The formation of GGPP is located in a C-terminal α-domain with very low sequence identity to the N-terminal Class I terpene

Phosphazene-catalyzed desymmetrization of cyclohexadienones by dithiane addition

• Matthew A. Horwitz,
• Elisabetta Massolo and
• Jeffrey S. Johnson

Beilstein J. Org. Chem. 2017, 13, 762–767, doi:10.3762/bjoc.13.75

• ] nucleophiles using bifunctional cinchona alkaloid catalysts. The Sasai and Enders groups used a phosphinothiourea to enable a Rauhut–Currier reaction to form bicyclic enones [16]. The Tian and Lin group used alkyne-tethered cyclohexadienones in an arylrhodation/conjugate addition sequence that

Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

Highly reactive, liquid diacrylamides via synergistic combination of spatially arranged curing moieties

• Maximilian Maier,
• Magnus S. Schmidt,
• Markus Ringwald and
• Christoph P. Fik

Beilstein J. Org. Chem. 2017, 13, 372–383, doi:10.3762/bjoc.13.40

• photoinitiation. Results and Discussion As stated earlier [24] we strive to investigate the unique physical properties and reactivity of tertiary N,N’-diallyl-diacrylamides. Closely related to this class of crosslinkers are bifunctional N-alkyl-N-allylacrylamides, which are known to undergo radical