Polydisperse methyl β-cyclodextrin–epichlorohydrin polymers: variable contact time ¹³C CP-MAS solid-state NMR characterization

• Isabelle Mallard,
• Davy Baudelet,
• Franca Castiglione,
• Monica Ferro,
• Walter Panzeri,
• Enzio Ragg and
• Andrea Mele

Beilstein J. Org. Chem. 2015, 11, 2785–2794, doi:10.3762/bjoc.11.299

• atoms in the molecular frame and whether regions of morphological heterogeneity exist or not. At this stage, it is important to stress two points: i) T1ρ describes the relaxation time of the 1H nuclei, and thus it is sensitive to hydrogen parameters only, including, as an example, the hydration state

Aggregation behaviour of amphiphilic cyclodextrins: the nucleation stage by atomistic molecular dynamics simulations

• Giuseppina Raffaini,
• Antonino Mazzaglia and
• Fabio Ganazzoli

Beilstein J. Org. Chem. 2015, 11, 2459–2473, doi:10.3762/bjoc.11.267

• secondary rim so as to maximize the P-chain hydration. It should also be noted that there is a small cluster of five water molecules trapped into the cavity, and quite isolated from the bulk water, with a pattern rather similar to what found in the native β-CD [46]. Interestingly, also in this case there is

• groups significantly cluster so as to minimize the contact with the environment, whereas the hydrophilic P groups show a marked opening to enhance their hydration. The ellipsoidal distortion of the macrocycle caused by the above mentioned interactions should also be noted. As a result, in water the

• for the tight clustering of the H groups to minimize the hydrated surface and for the wide opening of the P groups to maximize their hydration. In conclusion, even though one could denote this arrangement as a 2 + 1 + 1 aggregate, it is best described as a 3 + 1 aggregate. There is a further

Biocatalysis for the application of CO₂ as a chemical feedstock

• Apostolos Alissandratos and
• Christopher J. Easton

Beilstein J. Org. Chem. 2015, 11, 2370–2387, doi:10.3762/bjoc.11.259

• minimised [25][27]. By balancing thermodynamic feasibililty and a low requirement in NADH and ATP or equivalents, Milo and coworkers [25] were able to computationally predict the most efficient synthetic CO2 fixation pathways, using all known natural enzymes. Aqueous solubility and hydration of CO2 A

• . [117] were able to prove that this FDH utilises CO2, rather than HCO3−, as the active species, through experiments carried out at low temperatures where CO2 hydration is slow. The enzyme from Clostridium carboxidivorans was recombinantly expressed in E. coli and shown to display higher CO2 reducing

Evidencing an inner-sphere mechanism for NHC-Au(I)-catalyzed carbene-transfer reactions from ethyl diazoacetate

• Manuel R. Fructos,
• Juan Urbano,
• M. Mar Díaz-Requejo and
• Pedro J. Pérez

Beilstein J. Org. Chem. 2015, 11, 2254–2260, doi:10.3762/bjoc.11.245

• functionalization; olefin cyclopropanation; Introduction The discovery of the catalytic capabilities of soluble gold(I) species toward the hydration of alkynes by Teles and co-workers [1] is considered as the rising of the golden era for the use of this metal in homogeneous catalysis [2][3]. A number of

Influence of bulky yet flexible N-heterocyclic carbene ligands in gold catalysis

• Alba Collado,
• Scott R. Patrick,
• Danila Gasperini,
• Sebastien Meiries and
• Steven P. Nolan

Beilstein J. Org. Chem. 2015, 11, 1809–1814, doi:10.3762/bjoc.11.196

• selected: alkyne hydration, nitrile hydration, and the synthesis of homoallylic ketones. To place these results into context, [Au(IPr)(NTf2)] (10) [46] was also tested under the same conditions. Alkyne hydration Alkyne hydration is an attractive transformation to generate ketones from alkynes with high

• (10–1000 ppm) [51][52][53][56] have been achieved and the transformation has been successfully performed in aqueous media [54][57]. Due to its relevance and importance, the hydration of phenylacetylene was selected as a model transformation to explore the different activity of complexes 7–9. The

• obtained in all cases (Table 1, entries 5–8). However, the best conversion was observed when complex 10 bearing the IPr ligand was used (Table 1, entry 5). Complexes 7–9 afforded lower conversions, with [Au(IHept)(NTf2)] (8) being the most efficient amongst them (Table 1, entries 6–9). Nitrile hydration

Fates of imine intermediates in radical cyclizations of N-sulfonylindoles and ene-sulfonamides

• Hanmo Zhang,
• E. Ben Hay,
• Stephen J. Geib and
• Dennis P. Curran

Beilstein J. Org. Chem. 2015, 11, 1649–1655, doi:10.3762/bjoc.11.181

• Hanmo Zhang E. Ben Hay Stephen J. Geib Dennis P. Curran Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA 10.3762/bjoc.11.181 Abstract Two new fates of imine intermediates formed on radical cyclizations of ene-sulfonamides have been identified, reduction and hydration

• -dihydropyrroles also presumably form spiro-imines as primary products. However, the lactam carbonyl group facilitates the ring-opening of these cyclic imines by a new pathway of hydration and retro-Claisen-type reaction, providing rearranged 2-(2'-formamidoethyl)oxindoles. Keywords: ene-sulfonamide; imine

• substrates were chosen to provide imines with spirocyclic indoline and indolone substituents. We discovered that these imines are rather reactive, being either reduced or undergoing an unusual hydration and retro-Claisen-type reaction of an amide. Here we report the results of these experiments, which add to

Azobenzene-based inhibitors of human carbonic anhydrase II

• Leander Simon Runtsch,
• David Michael Barber,
• Peter Mayer,
• Michael Groll,
• Dirk Trauner and
• Johannes Broichhagen

Beilstein J. Org. Chem. 2015, 11, 1129–1135, doi:10.3762/bjoc.11.127

• ). Azobenzenes 1a and 1d have been synthesized and tested previously (with a CO2 hydration assay), and the Ki values determined in the previous work are one order of magnitude higher than in our findings (Ki (1a) = 665 nM or 29.7; Ki (1d) = 106 nM or 30.7) towards hCAII [6]. Interestingly, in our studies the

• hCAII. a) hCAII (pdb: 2vva [7]) catalyzes the hydration of carbon dioxide to bicarbonate and a proton (left) as well as the hydrolysis of pNPA to acetate and a colored phenolate (λmax = 400 nm). b) Aryl sulfonamide-containing pharmacophores of hCAII. c) Aryl sulfonamide merged to azobenzenes. Crystal

Terminal lipophilization of a unique DNA dodecamer by various nucleolipid headgroups: Their incorporation into artificial lipid bilayers and hydrodynamic properties

• Emma Werz and
• Helmut Rosemeyer

Beilstein J. Org. Chem. 2015, 11, 913–929, doi:10.3762/bjoc.11.103

• 12-mer DNA sequence using the Avogadro or the RasMol software. Half of the diameter corresponds to the half axis, b. Because nucleic acids bind water molecules and are, therefore, covered by a hydration shell, 2.8 Å is added to the radius b which is the diameter of a water molecule. The mean value of

• experimental and the calculated diffusion coefficients (Table 5, last column) is 1.45 ± 0.09 on average. Our data are comparable with those reported by Fernandes et al. in 2002 [23], which was also determined for DNA 12mers (1.22 and 1.45 × 10−6 cm2 s−1). Hydration of the lipo-oligonucleotides In an aqueous

• environment, water molecules form a hydration shell around the nucleic acid. Consequently, the surface of the nucleic acid chain is smoothed, and the partial volume of the hydrated molecule (Vhyd) is increased by the volume of the water shell. By determining the Vhyd of the LONs, one can calculate the degree

The Shono-type electroorganic oxidation of unfunctionalised amides. Carbon–carbon bond formation via electrogenerated N-acyliminium ions

• Alan M. Jones and
• Craig E. Banks

Beilstein J. Org. Chem. 2014, 10, 3056–3072, doi:10.3762/bjoc.10.323

• ]. The proposed formation of a bicyclic intermediate 18 resulting from a cycloaddition reaction would enhance the diastereoselectivity of the hydration step compared to an acyclic intermediate that would be formed in the step-wise mechanism to 18. The authors’ suggest the step-wise mechanism does play a

• role in reducing the diastereoselectivity of the reaction when the alkene is aryl- or alkyl-substituted. The hydration step can occur via pathway a or b to afford 17 (dr ca. 3:2). The N-acyliminium ions formed during an anodic oxidation of a silyl auxiliary can be coupled to a radical pathway using a

First chemoenzymatic stereodivergent synthesis of both enantiomers of promethazine and ethopropazine

• Paweł Borowiecki,
• Daniel Paprocki and
• Maciej Dranka

Beilstein J. Org. Chem. 2014, 10, 3038–3055, doi:10.3762/bjoc.10.322

• the active conformation of the enzyme molecule by destabilizing electrostatic interactions, and even strip off the essential water layer (water of hydration) leading to loss of the biocatalytic activity. In turn, more lipophilic organic solvents positively interact with the enzyme protein enhancing

Copper-promoted hydration and annulation of 2-fluorophenylacetylene derivatives: from alkynes to benzo[b]furans and benzo[b]thiophenes

• Yibiao Li,
• Liang Cheng,
• Xiaohang Liu,
• Bin Li and
• Ning Sun

Beilstein J. Org. Chem. 2014, 10, 2886–2891, doi:10.3762/bjoc.10.305

• Yibiao Li Liang Cheng Xiaohang Liu Bin Li Ning Sun School of Chemical & Environmental Engineering, Wuyi University, Jiangmen, Guangdong Province, 529090, China BASF Catalyst, 23800 Mercantile Road, Beachwood, Ohio 44124, USA 10.3762/bjoc.10.305 Abstract An efficient copper-promoted hydration

• reaction and its application in the synthesis of benzo[b]furan and benzo[b]thiophene derivatives is presented starting from readily available 2-fluorophenylacetylene derivatives. The key annulation step involves the hydration of the C–F bond of 2-fluorophenylacetylene derivatives followed by an

• product (Table 1, entry 1). The usage of CuCl and 1,10-phenanthroline (1,10-phen) as a ligand in CH3CN at 80 °C showed that 2a could be isolated in 35% yield (Table 1, entry 2). The screening of the various solvents revealed that the solvent played an important role in this hydration and annulation

Binding mode and free energy prediction of fisetin/β-cyclodextrin inclusion complexes

• Bodee Nutho,
• Wasinee Khuntawee,
• Chompoonut Rungnim,
• Piamsook Pongsawasdi,
• Peter Wolschann,
• Alfred Karpfen,
• Nawee Kungwan and
• Thanyada Rungrotmongkol

Beilstein J. Org. Chem. 2014, 10, 2789–2799, doi:10.3762/bjoc.10.296

• . From the atom–atom interaction RDF analysis, among all six oxygen atoms of fisetin in three complexes, no peak appeared within ~3 Å of the O1 atom, suggesting that this atom on the chromone ring has a relatively low water accessibility or very weak hydration interaction. Along the simulation this atom

• always seems to stay inside the hydrophobic cavity. Differentially, the other oxygen atoms show the first sharp peak centered at ~2.8 Å corresponding to a highly possible hydration and the first minimum at ~4 Å accounting for the time when a water molecule remains on the first solvation shell. On the

• -CD through the B-ring fitting at the narrow rim (complexes II–III), only the O7 atom on the A-ring was significantly higher solvated. The further discussion on the hydration of fisetin in complexation with β-CD is summarized as follows. Low hydration on the O3 atom (I–III: ~1.5, ~0.8 and ~0.6) was

Anomalous diffusion of Ibuprofen in cyclodextrin nanosponge hydrogels: an HRMAS NMR study

• Monica Ferro,
• Franca Castiglione,
• Carlo Punta,
• Lucio Melone,
• Walter Panzeri,
• Barbara Rossi,
• Francesco Trotta and
• Andrea Mele

Beilstein J. Org. Chem. 2014, 10, 2715–2723, doi:10.3762/bjoc.10.286

• , such as the chemical compositions of the nanosponge (e.g., CDNSPMA, CDNSEDTA are swellable, CDNSDPC are not) and the cross-linker to CD mole ratio n [17]. Recently, we demonstrated that the CDNS hydrogels undergo phase transitions by changing the hydration level h = m(H2O)/mCDNS by a complex interplay

Phosphinocyclodextrins as confining units for catalytic metal centres. Applications to carbon–carbon bond forming reactions

• Matthieu Jouffroy,
• Rafael Gramage-Doria,
• David Sémeril,
• Dominique Armspach,
• Dominique Matt,
• Werner Oberhauser and
• Loïc Toupet

Beilstein J. Org. Chem. 2014, 10, 2388–2405, doi:10.3762/bjoc.10.249

• , 2JC,P = 22.8 Hz, CO) ppm; 31P{1H} NMR (161.9 MHz, CDCl3, 25 °C) δ 40.5 (d, 1JP,Rh = 172 Hz) ppm; IR: 2086 (vs, CO), 2026 (vs, CO), 2004 (s, CO) cm−1; We do not provide microanalytical data for this compound because of strong hydration; MS (ESI–TOF): m/z (%): 1799.44 (70) [M – Cl]+, 1857.40 (100) [M

Pyrrolidine nucleotide analogs with a tunable conformation

• Lenka Poštová Slavětínská,
• Dominik Rejman and
• Radek Pohl

Beilstein J. Org. Chem. 2014, 10, 1967–1980, doi:10.3762/bjoc.10.205

• alternate between A, B and Z forms depending on the hydration and the type and concentration of metal ions, which is also reflected in the conformation of the sugar part. Finally, the conformation of ribose or its mimics also significantly predetermines the binding of a nucleoside, nucleotide or an analog

Synthesis of trifluoromethyl-substituted pyrazolo[4,3-c]pyridines – sequential versus multicomponent reaction approach

• Barbara Palka,
• Angela Di Capua,
• Maurizio Anzini,
• Gyté Vilkauskaité,
• Algirdas Šačkus and
• Wolfgang Holzer

Beilstein J. Org. Chem. 2014, 10, 1759–1764, doi:10.3762/bjoc.10.183

• the corresponding ketones. The hydration of C–C triple bonds under the influence of various catalytic systems, including also Pd-based catalysts, is a well-known reaction [21][22]. It should be emphasized that NMR investigations with compounds 8a,c unambiguously revealed the methylene group adjacent

The search for new amphiphiles: synthesis of a modular, high-throughput library

• George C. Feast,
• Thomas Lepitre,
• Xavier Mulet,
• Charlotte E. Conn,
• Oliver E. Hutt,
• G. Paul Savage and
• Calum J. Drummond

Beilstein J. Org. Chem. 2014, 10, 1578–1588, doi:10.3762/bjoc.10.163

• layer of amphiphile prior to hydration of the material. The microscope slide was placed into a Linkam PE94 hot stage (Linkam Scientific Instruments Ltd.; Surrey, England) and a water drop added at the side of the cover slip to flood the sample and create a concentration gradient as water was absorbed

Molecular recognition of surface-immobilized carbohydrates by a synthetic lectin

• Melanie Rauschenberg,
• Eva-Corrina Fritz,
• Christian Schulz,
• Tobias Kaufmann and
• Bart Jan Ravoo

Beilstein J. Org. Chem. 2014, 10, 1354–1364, doi:10.3762/bjoc.10.138

• as drugs in various therapies and as recognition units in diagnostics and sensing. However, the development of synthetic lectins poses a phenomenal challenge for supramolecular chemistry [37] because a carbohydrate receptor in order to be useful must not only compete with the strong hydration of

Staudinger ligation towards cyclodextrin dimers in aqueous/organic media. Synthesis, conformations and guest-encapsulation ability

• Malamatenia D. Manouilidou,
• Yannis G. Lazarou,
• Irene M. Mavridis and
• Konstantina Yannakopoulou

Beilstein J. Org. Chem. 2014, 10, 774–783, doi:10.3762/bjoc.10.73

• both β-CD cavities (Figure 3d) are the least stable by PM3(COSMO) (in the presence of water), although highly favorable by PM3 (in the absence of solvent). This was attributed to insufficient hydration of the primary hydroxy groups due to steric crowding around the primary sides of the two β-CD tori

Integration of enabling methods for the automated flow preparation of piperazine-2-carboxamide

• Richard J. Ingham,
• Claudio Battilocchio,
• Joel M. Hawkins and
• Steven V. Ley

Beilstein J. Org. Chem. 2014, 10, 641–652, doi:10.3762/bjoc.10.56

• treatment of tuberculosis – and its reduced derivative piperazine-2-carboxamide. Keywords: automation; flow chemistry; hydration; hydrogenation; sustainable processing; Introduction Enabling synthesis technologies such as flow chemistry are becoming commonplace in modern laboratories (for recent reviews

• explored the possibility of developing a machine-automated synthesis of this compound which might later be extended to analogous structures. For the facile machine-assisted synthesis of 1 we devised and optimised the fully continuous sequential hydration of nitrile 3 to amide 2 and hydrogenation of

• pyrazine 2 to piperazine 1 (Figure 2b). Both of these steps involve flowing through heterogeneous catalysts, a metal oxide for the hydration of the nitrile and a supported precious metal for the hydrogenation of the heteroaromatic ring. Furthermore, both steps involve the addition of a volatile small

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

Ambient gold-catalyzed O-vinylation of cyclic 1,3-diketone: A vinyl ether synthesis

• Yumeng Xi,
• Boliang Dong and
• Xiaodong Shi

Beilstein J. Org. Chem. 2013, 9, 2537–2543, doi:10.3762/bjoc.9.288

• as essential tools in organic synthesis. Generally with the unique reactivity and mild reaction conditions, this type of transformation has found widespread applications in complex molecule synthesis [10][11]. Among those reactions, the gold-catalyzed hydration of alkynes is regarded as one of the

• signature reactions in the field (known as Teles hydration) [12]. This reaction usually utilized the combination of methanol and water, wherein methanol served as the nucleophile to attack the triple bond, forming the vinyl ether intermediate. This vinyl ether then collapsed to give a ketone as the final

• 1,3-diketones with unactivated alkynes at ambient temperature. Results and Discussion As indicated in Scheme 1, the main challenge for the intermolecular O-nucleophile addition to alkynes is the competitive hydration side reaction. Although, theoretically, strictly anhydrous conditions shall prevent

Recent advances in transition metal-catalyzed Csp²-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation

• Grégory Landelle,
• Armen Panossian,
• Sergiy Pazenok,
• Jean-Pierre Vors and
• Frédéric R. Leroux

Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287

• fluorine, its hydration and thus reduced nucleophilicity [21]. The importance of this developing research field is reflected by the various review articles which have been published dealing with transition metal mediated or catalyzed fluorination [22][23][24], difluoromethylation [24], and

The chemistry of isoindole natural products

• Klaus Speck and
• Thomas Magauer

Beilstein J. Org. Chem. 2013, 9, 2048–2078, doi:10.3762/bjoc.9.243

• condensation of primary amines with o-diacylbenzene 19 (Scheme 2) [13]. After initial formation of 20, isomerization to 21 and 22 can occur through a sequential dehydration–hydration process. Dimerization of 21 and 22 generates 23, the substrate for a formal retro-Aldol reaction. Loss of formaldehyde gives 24

A concise enantioselective synthesis of the guaiane sesquiterpene (−)-oxyphyllol

• Martin Zahel and
• Peter Metz

Beilstein J. Org. Chem. 2013, 9, 2028–2032, doi:10.3762/bjoc.9.239

• the total synthesis of the anticancer guaiane (−)-englerin A. A regio- and diastereoselective Co(II)-catalyzed hydration of the olefin and a transannular epoxide opening were used as the key reactions. Keywords: asymmetric synthesis; hydration; natural products; terpenes; transannular epoxide opening

• completion of the synthesis of (−)-oxyphyllol (1) from 4. To our delight, a direct regio- and diastereoselective Co(II)-catalyzed hydration [12] of the olefin in 4 succeeded to give the required α-stereoisomer 3 in 58% isolated yield after chromatographic separation of the minor β-alcohol. Compared to the