A new method for the synthesis of α-aminoalkylidenebisphosphonates and their asymmetric phosphonyl-phosphinyl and phosphonyl-phosphinoyl analogues

• Anna Kuźnik,
• Roman Mazurkiewicz,
• Mirosława Grymel,
• Katarzyna Zielińska,
• Jakub Adamek,
• Ewa Chmielewska,
• Marta Bochno and
• Sonia Kubica

Beilstein J. Org. Chem. 2015, 11, 1418–1424, doi:10.3762/bjoc.11.153

• and biological activity of 1-phosphinylalkylphosphonates, including their most interesting 1-hydroxy and 1-amino derivatives (Figure 2, 2 and 3, respectively; R = H, Alk, Ar). In 1990, Ebetino et al. described both a contiguous and stepwise strategy for the synthesis of the pyridylaminomethane-based

• orthoformate, diethyl phosphite and monoethyl methylphosphonite, followed by chromatographic separation of the three possible condensation products and the final hydrolysis, gave the expected phosphinylalkylphosphonic acid in only 17% yield [20]. The stepwise method consisted in the condensation of diethyl

The chemical behavior of terminally tert-butylated polyolefins

• Dagmar Klein,
• Henning Hopf,
• Peter G. Jones,
• Ina Dix and
• Ralf Hänel

Beilstein J. Org. Chem. 2015, 11, 1246–1258, doi:10.3762/bjoc.11.139

• amounts of 9 and 10 grew at the cost of 8, and when the hydrogenation was run for two days, alkane 10 was the only reduction product. It seems safe to assume that we are dealing with a stepwise process, with 8 and 9 serving as intermediates en route to 10. Comparing the two experiments starting from 3 and

Glycoluril–tetrathiafulvalene molecular clips: on the influence of electronic and spatial properties for binding neutral accepting guests

• Yoann Cotelle,
• Marie Hardouin-Lerouge,
• Stéphanie Legoupy,
• Olivier Alévêque,
• Eric Levillain and
• Piétrick Hudhomme

Beilstein J. Org. Chem. 2015, 11, 1023–1036, doi:10.3762/bjoc.11.115

• . The stepwise oxidation of each molecular clip involves an electrochemical mechanism with three one-electron processes and two charge-coupled chemical reactions, a scheme which is supported by electrochemical simulations. The fine-tunable π-donating ability of the TTF units and the cavity size allow to

• supports the graphical representation of the stepwise oxidation of molecular clips 1, 2 and 3 (Scheme 3). Optical and spectroelectrochemical properties The optical properties of oxidized states of molecular clip 1 were monitored by UV–vis–NIR spectroscopy, by successive aliquot addition of NOSbF6 (5 × 10−3

• −1, kf = 1 × 109 M−1·s−1 for all the forward reactions, α = 0.5 and ks = 0.01 cm·s−1 for all the charge transfers). Molecular structure of molecular clip 15 and representation of its stepwise oxidation processes proposed by Chiu et al. [58]. Molecular packing diagram of clips 2 (left) and 3 (right

Interactions between tetrathiafulvalene units in dimeric structures – the influence of cyclic cores

• Huixin Jiang,
• Virginia Mazzanti,
• Christian R. Parker,
• Søren Lindbæk Broman,
• Jens Heide Wallberg,
• Karol Lušpai,
• Adam Brincko,
• Henrik G. Kjaergaard,
• Anders Kadziola,
• Peter Rapta,
• Ole Hammerich and
• Mogens Brøndsted Nielsen

Beilstein J. Org. Chem. 2015, 11, 930–948, doi:10.3762/bjoc.11.104

• structure, as in the radiaannulene 2a, communication between the two TTFs is observed in the cyclic voltammetry experiment, and the first two-electron event showed the waves diverging from each other (two stepwise oxidations) [10]. In addition, the intermediate radical cation showed an IVCT absorption at

• oxidations were reported [6]. For the radiaannulene 2a removal of two electrons was previously [10] found to occur stepwise with a separation between the first and second oxidations of 90 mV. Thus, despite the long gem-TEE bridging units, there is a weak interaction between the TTFs that are separated by a

• close together by a single bridge does not by itself seem to increase significantly the electronic communication when stepwise oxidations are used as a measure hereof. Instead, fusing directly together the two TTF units, connecting them to a benzene or pyrazine ring, or even to a larger radiaannulene

Mechanical stability of bivalent transition metal complexes analyzed by single-molecule force spectroscopy

• Manuel Gensler,
• Christian Eidamshaus,
• Maurice Taszarek,
• Hans-Ulrich Reissig and
• Jürgen P. Rabe

Beilstein J. Org. Chem. 2015, 11, 817–827, doi:10.3762/bjoc.11.91

• aqueous solutions of CuSO4 (Figure 1). As a result, rupture forces of both valencies were similar. Combining DFS with ab-initio calculations we suggested a stepwise bond-rupture including a hydrogen-bound intermediate. Thus in our system the bivalent effect did not increase the mechanical stability, but

• transition state is rate dominating. However the KBE model fit for the stepwise process would only extrapolate to the thermal off-rate of the first transition state, gaining the value for a monovalent interaction. Thus in the following discussions we will suggest a simultaneous rupture. The lower thermal off

• -rate of the flexible pyridine 2c compared to 1 also indicates a bivalent interaction. In contrast to 2b, the rupture length is much larger and we suggest a stepwise bond rupture such as PED II in Figure 3. Still the rupture length of 1.12 nm is too large to be described by the known hydrogen-bound

Impact of multivalent charge presentation on peptide–nanoparticle aggregation

• Daniel Schöne,
• Boris Schade,
• Christoph Böttcher and
• Beate Koksch

Beilstein J. Org. Chem. 2015, 11, 792–803, doi:10.3762/bjoc.11.89

• , it can be assumed that incubation with R2A2 leads to an aggregation of Au/MUA nanoparticles. A stepwise increase in the sequence length by adding one heptad repeat without changing the amount of arginine residues (R2A3) leads to a comparable effect (Figure 4E). In contrast, increasing the incubation

• mobility of Au/MUA nanoparticles (Figure 6). On the other hand, the mobility of the Au/MUA nanoparticle band only slightly decreases when R1A3 is present; even a very high concentration of peptide R1A3 (200 µm) does not change this finding. All other peptides cause a stepwise decrease in Au/MUA

• charges is reduced in R2A2. The stepwise increase in peptide length induced a dramatic decrease of the KB value. However, the KB of R2A3 is slightly higher compared to VW05. Only a further increase in peptide length lead to a significant decrease in the binding constant compared to VW05. Although gel

Multivalent polyglycerol supported imidazolidin-4-one organocatalysts for enantioselective Friedel–Crafts alkylations

• Tommaso Pecchioli,
• Manoj Kumar Muthyala,
• Rainer Haag and
• Mathias Christmann

Beilstein J. Org. Chem. 2015, 11, 730–738, doi:10.3762/bjoc.11.83

• of solid support such as polystyrene may lead to the disadvantage of operating in heterogeneous media. In contrast to the stepwise syntheses of dendrimers and dendron hybrids, the hyperbranched polymers can be easily obtained in kilogram scale through one-pot reactions [10], maintaining properties

Weakly nucleophilic potassium aryltrifluoroborates in palladium-catalyzed Suzuki–Miyaura reactions: relative reactivity of K[4-RC₆F₄BF₃] and the role of silver-assistance in acceleration of transmetallation

• Vadim V. Bardin,
• Anton Yu. Shabalin and
• Nicolay Yu. Adonin

Beilstein J. Org. Chem. 2015, 11, 608–616, doi:10.3762/bjoc.11.68

• anhydrous THF in the presence of trialkylamine as a base or in alcohols [4]. Alternatively, the Pd-catalyzed cross-coupling of K[ArBF3] in aqueous THF is proved to proceed through stepwise hydrolysis to produce more reactive [ArBFn(OH)3-n]− or ArB(OH)2 [35][38]. However, special experiments showed that K

On the strong difference in reactivity of acyclic and cyclic diazodiketones with thioketones: experimental results and quantum-chemical interpretation

• Andrey S. Mereshchenko,
• Alexey V. Ivanov,
• Viktor I. Baranovskii,
• Grzegorz Mloston,
• Ludmila L. Rodina and
• Valerij A. Nikolaev

Beilstein J. Org. Chem. 2015, 11, 504–513, doi:10.3762/bjoc.11.57

• through the single minimum energy transition state, TS1. This observation implies that the cycloaddition reaction proceeds via a concerted mechanism. In the case of an alternative, stepwise mechanism, one would expect the appearance of at least two transition states [29], which was not observed. In

Sequence-specific RNA cleavage by PNA conjugates of the metal-free artificial ribonuclease tris(2-aminobenzimidazole)

• Friederike Danneberg,
• Alice Ghidini,
• Plamena Dogandzhiyski,
• Elisabeth Kalden,
• Roger Strömberg and
• Michael W. Göbel

Beilstein J. Org. Chem. 2015, 11, 493–498, doi:10.3762/bjoc.11.55

• approach towards tris(2-aminobenzimidazole), we adopted Lipton's method to the synthesis of aminobenzimidazoles. Thiourea 3 was prepared as described before [15], starting with the Boc-protection of tris(2-aminoethyl)amine (1) followed by the stepwise reaction of the free NH2 group of product 2 with

Attempts to prepare an all-carbon indigoid system

• Şeref Yildizhan,
• Henning Hopf and
• Peter G. Jones

Beilstein J. Org. Chem. 2015, 11, 363–372, doi:10.3762/bjoc.11.42

• , obtained when 21 was subjected to a crossed McMurry coupling with excess acetone. In a stepwise approach, 21 was treated with either methyllithium in ether or methylmagnesium bromide in the hope of either preparing a mono- or the bis-tertiary alcohol derivative 20, which subsequently could be subjected to

• omitted. From indigo to heteroindigo derivatives and all-carbon-indigo. Attempts to prepare the α-methylene ketones 12 and 13. Dimerization of 13 under McMurry conditions. Dimerization of indan-1-one (18) by a stepwise approach. Methylenation of 19 and bisalkylation of the product 23 with 1,2

Anionic sigmatropic-electrocyclic-Chugaev cascades: accessing 12-aryl-5-(methylthiocarbonylthio)tetracenes and a related anthra[2,3-b]thiophene

• Laurence Burroughs,
• John Ritchie,
• Mkhethwa Ngwenya,
• Dilfaraz Khan,
• William Lewis and
• Simon Woodward

Beilstein J. Org. Chem. 2015, 11, 273–279, doi:10.3762/bjoc.11.31

• , stepwise synthesis of a family of acene derivatives from various acyclic precursors is normally very step intensive. The prevalence of these issues in the synthesis of substituted tetracenes caused Lin [14], building on the anthracycline natural product work of Saá [15], to introduce a 1,2-bis-allene

Synthesis and characterization of a new photoinduced switchable β-cyclodextrin dimer

• Florian Hamon,
• Claire Blaszkiewicz,
• Marie Buchotte,
• Estelle Banaszak-Léonard,
• Hervé Bricout,
• Sébastien Tilloy,
• Eric Monflier,
• Christine Cézard,
• Laurent Bouteiller,
• Christophe Len and
• Florence Djedaini-Pilard

Beilstein J. Org. Chem. 2014, 10, 2874–2885, doi:10.3762/bjoc.10.304

• (λ = 365 nm) for the irradiation of aqueous AZO-CDim 1 solutions (c = 10−4 M). Stepwise control of the reactions was readily achieved by ESIMS in the positive ion mode using a ZQ 4000 quadrupole mass spectrometer (Waters-Micromass, Manchester, UK). High resolution electrospray mass spectra (HRMS–ESI

Recent advances in the electrochemical construction of heterocycles

• Robert Francke

Beilstein J. Org. Chem. 2014, 10, 2858–2873, doi:10.3762/bjoc.10.303

• , yielding either the cis- or trans-cycloadduct exclusively. Consistent with the results of computational studies conducted by the authors, this stereospecifity points towards a concerted reaction mechanism. In contrast, cycloaddition of phenyl-substituted olefins seems to proceed via a stepwise mechanism

Synthesis of graft polyrotaxane by simultaneous capping of backbone and grafting from rings of pseudo-polyrotaxane

• Kazuaki Kato,
• Katsunari Inoue,
• Masabumi Kudo and
• Kohzo Ito

Beilstein J. Org. Chem. 2014, 10, 2573–2579, doi:10.3762/bjoc.10.269

• base prevents hydrogen bond formation between the α-CDs. Meanwhile, prevention of the hydrogen bond formation is necessary for the α-CDs to access the monomers. Therefore, the kinetic control of both the dissociation of the hydrogen bonds and the polymerization is necessary. A stepwise increase in the

Autonomous assembly of synthetic oligonucleotides built from an expanded DNA alphabet. Total synthesis of a gene encoding kanamycin resistance

• Kristen K. Merritt,
• Kevin M. Bradley,
• Daniel Hutter,
• Mariko F. Matsuura,
• Diane J. Rowold and
• Steven A. Benner

Beilstein J. Org. Chem. 2014, 10, 2348–2360, doi:10.3762/bjoc.10.245

• were defective, smaller constructs were self-assembled. Figure 8 shows the results of stepwise assembly of subsets of the fragments, after the target ligation products were rescued from the mixture by PCR (30 cycles). As is evident by the intensity of the bands arising from the amplicons four, eight

• convergent synthesis after blunt-end ligation. The desired 1,135 base-pair target construct was recovered by PCR (see Supporting Information File 1, Figure S4). This process was, of course, not automated; it represented the same stepwise convergent assembly of L-DNA that has been reported previously [3][4][5

Specific DNA duplex formation at an artificial lipid bilayer: fluorescence microscopy after Sybr Green I staining

• Emma Werz and
• Helmut Rosemeyer

Beilstein J. Org. Chem. 2014, 10, 2307–2321, doi:10.3762/bjoc.10.240

• Figure 7 it can be seen that a stepwise mixing of the lipo-oligonucleotide 4 and the complementary strand 6 with an intermediary incubation of 43 min for an optimal insertion of 4 into the bilayer, followed by a further waiting period (41 min) for duplex formation leads to a bilayer brightness of 70

Reversibly locked thionucleobase pairs in DNA to study base flipping enzymes

• Christine Beuck and
• Elmar Weinhold

Beilstein J. Org. Chem. 2014, 10, 2293–2306, doi:10.3762/bjoc.10.239

• -Et-S4U2) were added stepwise increasing amounts of a solution containing M.TaqI (10 µM), 36mer duplex with 2AP (200 nM) and a duplex 1I6S·2U4S or 1I6S-Et-S4U2 (400 nM) in the same buffers. The relative fluorescence intensity was determined after each addition. A model with one binding site and two

A new charge-tagged proline-based organocatalyst for mechanistic studies using electrospray mass spectrometry

• J. Alexander Willms,
• Rita Beel,
• Martin L. Schmidt,
• Christian Mundt and
• Marianne Engeser

Beilstein J. Org. Chem. 2014, 10, 2027–2037, doi:10.3762/bjoc.10.211

• its tert-butyl blocked carboxylic acid function. The fragmentation of [II*b]+ exclusively consists of a loss of [C5,H8,O2] which should correspond to a concerted or very fast stepwise elimination of isobutene and CO2 leading to the same product ion at m/z 323.21 as the expulsion of CO2 from m/z 367.20

OligArch: A software tool to allow artificially expanded genetic information systems (AEGIS) to guide the autonomous self-assembly of long DNA constructs from multiple DNA single strands

• Kevin M. Bradley and
• Steven A. Benner

Beilstein J. Org. Chem. 2014, 10, 1826–1833, doi:10.3762/bjoc.10.192

• assembly typically failed between 16 and 24 oligonucleotides. Other methods of assembly, such as the Gibson Assembly [7] or SLIC [8], either limit the number of fragments to be used or rely on stepwise assembly of such syntheses, with the recommendation from Gibson that autonomous self-assembly of single

Sacrolide A, a new antimicrobial and cytotoxic oxylipin macrolide from the edible cyanobacterium Aphanothece sacrum

• Naoya Oku,
• Miyako Matsumoto,
• Kohsuke Yonejima,
• Keijiroh Tansei and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2014, 10, 1808–1816, doi:10.3762/bjoc.10.190

• further separated between H2O (200 mL) and n-BuOH (200 mL × 3). The most active aqueous MeOH layer (422.9 mg) was subjected to silica gel chromatography with a stepwise elution by n-hexane/EtOAc 4:1, 2:1, 1:1, 1:2, 1:4, chloroform/MeOH 99:1, 97:3, 95:5, 9:1, and chloroform/MeOH/H2O 6:4:1 to give ten

Theoretical study of the adsorption of benzene on coinage metals

• Werner Reckien,
• Melanie Eggers and
• Thomas Bredow

Beilstein J. Org. Chem. 2014, 10, 1775–1784, doi:10.3762/bjoc.10.185

• atoms. Potential curves are obtained on the basis of single-point calculations with the PBE-D3, PBE-D3(BJ), PBE-D3(ABC), RPBE-D3, RevPBE-D3(BJ) and RPBE-D3 approaches. We stepwise altered the distance between the benzene molecule and the unrelaxed surface from 2.5 Å to 5.0 Å. Since d1 and d2 do not

• the scope of the present study. We also checked that the orientation of the flat lying molecules with respect to the underlying surfaces has no significant influence to the adsorption energies and geometries: A stepwise rotation of the molecule around the z-axis changes Eads by less than 1 kJ/mol in

Convergent synthetic methodology for the construction of self-adjuvanting lipopeptide vaccines using a novel carbohydrate scaffold

• Vincent Fagan,
• Istvan Toth and
• Pavla Simerska

Beilstein J. Org. Chem. 2014, 10, 1741–1748, doi:10.3762/bjoc.10.181

• previously reported carbohydrate-based vaccine constructs [11] were prepared by a divergent approach, where the carbohydrate core was coupled to the resin-bound LCP adjuvanting moiety, followed by stepwise synthesis of the B cell epitopes using solid-phase peptide synthesis (SPPS). Using this divergent

• and RP-HPLC (Supporting Information File 1). After the successful synthesis of vaccine candidate 10, further complexity was introduced into this system. In this case, following the synthesis of LLCP, stepwise SPPS was continued in order to incorporate a T-helper epitope (Pan DR Epitope; PADRE

Aryl substitution of pentacenes

• Andreas R. Waterloo,
• Anna-Chiara Sale,
• Dan Lehnherr,
• Frank Hampel and
• Rik R. Tykwinski

Beilstein J. Org. Chem. 2014, 10, 1692–1705, doi:10.3762/bjoc.10.178

• -substituted pentacenes, we were interested in the influence of different aryl moieties directly linked to the pentacene core. In this work we present a simple synthetic approach to unsymmetrically substituted pentacenes via stepwise functionalization of pentacenequinone, using a nucleophilic aryl group

Photoswitchable precision glycooligomers and their lectin binding

• Daniela Ponader,
• Sinaida Igde,
• Marko Wehle,
• Katharina Märker,
• Mark Santer,
• David Bléger and
• Laura Hartmann

Beilstein J. Org. Chem. 2014, 10, 1603–1612, doi:10.3762/bjoc.10.166

• the combination of solid phase polymer synthesis and tailor-made building blocks [7][8][9]. Through a stepwise assembly of our functional building blocks, we can now control the kind, number, and spacing of sugar ligands along a monodisperse scaffold. Thus, our precision glycomacromolecules allow for

• %/70% MeCN/H2O in 60 min) tR = 14.1 min; ESIMS [M + 2H]2 calcd for C87H148N24O36, 1053.5; found, 1053.8, [M + 3H]3+ 702.7; found, 702.8, [M + 4H]4+ 527.3; found, 527.4, [M + 5H]5+ 422.0; found, 422.2. Synthesis of photoswitchable precision glycooligomers via stepwise addition of building blocks on