Evidence for an iterative module in chain elongation on the azalomycin polyketide synthase

• Hui Hong,
• Yuhui Sun,
• Yongjun Zhou,
• Emily Stephens,
• Markiyan Samborskyy and
• Peter F. Leadlay

Beilstein J. Org. Chem. 2016, 12, 2164–2172, doi:10.3762/bjoc.12.206

• also neatly explains how the diversity of naturally-occurring complex polyketides is generated by a common biosynthetic mechanism, and provides clues to the evolution of these multienzymes through duplication, capture, deletion, and rearrangement of modules or individual domains [5]. It has both

• ) animal fatty acid synthases and that on bacterial modular polyketide synthases, and it also hints at what could be a major mechanism for the evolution of these processive systems. Nevertheless, the highly repetitive nature of the genes encoding modular PKS makes it easy to misassemble sequence data, and

Comparing blends and blocks: Synthesis of partially fluorinated diblock polythiophene copolymers to investigate the thermal stability of optical and morphological properties

• Pierre Boufflet,
• Sebastian Wood,
• Jessica Wade,
• Zhuping Fei,
• Ji-Seon Kim and
• Martin Heeney

Beilstein J. Org. Chem. 2016, 12, 2150–2163, doi:10.3762/bjoc.12.205

• before rapid quench cooling. The evolution of the thin film UV–visible absorption spectra with increasing annealing temperature (see Figure 5) partly reflects the thermal behavior of the samples as observed by DSC. In all cases, the low energy shoulder decreases in intensity with increasing annealing

• absorption spectroscopy, we performed in situ Raman spectroscopy measurements, similar to those previously carried out on P3OT and F-P3OT [42] in order to observe the evolution of intramolecular order with temperature, and compare the block copolymers with the polymer blends. The room temperature Raman

Effect of the π-conjugation length on the properties and photovoltaic performance of A–π–D–π–A type oligothiophenes with a 4,8-bis(thienyl)benzo[1,2-b:4,5-b′]dithiophene core

• Ni Yin,
• Lilei Wang,
• Yi Lin,
• Jinduo Yi,
• Lingpeng Yan,
• Junyan Dou,
• Hai-Bo Yang,
• Xin Zhao and
• Chang-Qi Ma

Beilstein J. Org. Chem. 2016, 12, 1788–1797, doi:10.3762/bjoc.12.169

• presents the evolution of VOC, JSC, FF and PCE of un-encapsulated COOP-nHT-TBDT:PC61BM cells tested in N2 atmosphere under continuous illumination. To fully simulate the degradation behaviour of solar cells under working conditions, an external load to match the maximum power output point (mpp) was

Mutagenic activity of quaternary ammonium salt derivatives of carbohydrates

• Barbara Dmochowska,
• Karol Sikora,
• Anna Woziwodzka,
• Jacek Piosik and
• Beata Podgórska

Beilstein J. Org. Chem. 2016, 12, 1434–1439, doi:10.3762/bjoc.12.138

• Faculty of Biotechnology, University of Gdańsk and Medical University of Gdańsk, Antoniego Abrahama 58, 80-307 Gdańsk, Poland Department of Molecular Evolution, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk, Poland 10.3762/bjoc.12.138 Abstract This paper presents a study on a series of quaternary

Synthesis of ferrocenyl-substituted 1,3-dithiolanes via [3 + 2]-cycloadditions of ferrocenyl hetaryl thioketones with thiocarbonyl S-methanides

• Grzegorz Mlostoń,
• Róża Hamera-Fałdyga,
• Anthony Linden and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2016, 12, 1421–1427, doi:10.3762/bjoc.12.136

• mixture was heated at 45 °C until the evolution of N2 ceased. Then, the solvent was evaporated and the crude products were purified by CC (SiO2, hexane/ethyl acetate 95:5). The major product was isolated using diethyl ether (precipitation). 4-Ferrocenyl-5,5-diphenyl-4-(selenophen-2-yl)-1,3-dithiolane (5c

Ring-whizzing in polyene-PtL₂ complexes revisited

• Oluwakemi A. Oloba-Whenu,
• Thomas A. Albright and
• Chirine Soubra-Ghaoui

Beilstein J. Org. Chem. 2016, 12, 1410–1420, doi:10.3762/bjoc.12.135

• , therefore, 6 can always interact with it. On the other hand, the LUMO in the π system may not always have the correct symmetry to interact with the b2 orbital on ML2 and it is the evolution of this overlap that has an important impact on the reaction path and activation energy. We will also have an occasion

Diradical reaction mechanisms in [3 + 2]-cycloadditions of hetaryl thioketones with alkyl- or trimethylsilyl-substituted diazomethanes

• Grzegorz Mlostoń,
• Paulina Pipiak and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2016, 12, 716–724, doi:10.3762/bjoc.12.71

• assumption that they occur via diradical intermediates [13][14][15]. Reactions of aromatic thioketones with diazomethane are well established. For example, in the case of thiobenzophenone (1a), the reaction performed at –65 ºC occurs without evolution of N2 and the in situ formed 2,2-diphenyl-1,3,4

• -thiadiazoline 2a can be subsequently used as a precursor of the reactive thiobenzophenone S-methanide (a thiocarbonyl ylide) 3a at ca. −45 °C, when the evolution of N2 takes place [16][17][18][19][20]. An analogous course of the reaction with diazomethane was observed in the case of thiofluorenone (1b, Scheme 1

• -oxathiolanes, 1,3-dithiolanes, etc. Results and Discussion The first experiment performed with thiobenzophenone (1a) and 2-diazopropane (7a) at ca. −75 °C in THF led to a change of the blue color of the solution without evolution of N2. The addition of the solution of 7a was continued until the color of the

Elucidation of a masked repeating structure of the O-specific polysaccharide of the halotolerant soil bacteria Azospirillum halopraeferens Au4

• Elena N. Sigida,
• Yuliya P. Fedonenko,
• Alexander S. Shashkov,
• Nikolay P. Arbatsky,
• Evelina L. Zdorovenko,
• Svetlana A. Konnova,
• Vladimir V. Ignatov and
• Yuriy A. Knirel

Beilstein J. Org. Chem. 2016, 12, 636–642, doi:10.3762/bjoc.12.62

• calibration. Two-dimensional NMR experiments were performed using standard Bruker software. Spin lock time in TOCSY experiments and mixing time in ROESY experiments were set to 60 and 200 ms, respectively. The HMBC spectrum was recorded with a 60-ms delay for evolution of long-range couplings. Samples were

Biosynthesis of α-pyrones

• Till F. Schäberle

Beilstein J. Org. Chem. 2016, 12, 571–588, doi:10.3762/bjoc.12.56

• biosynthesis of these mostly polyketide-derived structures exist, thus it is assumed that the route towards α-pyrones has been developed several times in evolution. They can be built up by the catalytic activities of the different types of polyketide synthase (PKS) systems, and especially the final ring

Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions

• Rajeev S. Menon,
• Akkattu T. Biju and
• Vijay Nair

Beilstein J. Org. Chem. 2016, 12, 444–461, doi:10.3762/bjoc.12.47

• electrophiles (nitroso compounds) are some of the developments that revamped the synthetically unattractive, monotonous image of benzoin condensations. The driving force behind this remarkable evolution of benzoin reaction is NHC-catalysis. Benzoin chemistry is well-set to benefit, in the near future, from new

Dynamic behavior of rearranging carbocations – implications for terpene biosynthesis

• Stephanie R. Hare and
• Dean J. Tantillo

Beilstein J. Org. Chem. 2016, 12, 377–390, doi:10.3762/bjoc.12.41

• have pointed to the possibility that inherent dynamical tendencies of reactive intermediates may play important roles in enzyme evolution. Here we review key studies on the dynamical behavior of carbocations. First we provide an introduction to dynamical behavior and how it is examined using modern

Art, auto-mechanics, and supramolecular chemistry. A merging of hobbies and career

• Eric V. Anslyn

Beilstein J. Org. Chem. 2016, 12, 362–376, doi:10.3762/bjoc.12.40

• /kandinsky) , with orbitals computed by John Stanton (personal communication). Collage created by EVA. A potpourri of chemical receptor designs that influenced our group’s work 1, 2, 5, 6, 7, 8), along with a few of our own (3 and 4) [34][35][36][37][38][39][40][41][42][43][44][45]. Evolution of design of

Natural products from microbes associated with insects

• Christine Beemelmanns,
• Huijuan Guo,
• Maja Rischer and
• Michael Poulsen

Beilstein J. Org. Chem. 2016, 12, 314–327, doi:10.3762/bjoc.12.34

• Christine Beemelmanns Huijuan Guo Maja Rischer Michael Poulsen Leibniz Institute for Natural Product Research and Infection Biology e.V., Beutenbergstrasse 11a, 07745 Jena, Germany Centre for Social Evolution, Section for Ecology and Evolution, Department of Biology, University of Copenhagen

• light on the ecology and evolution of defensive associations. Keywords: biosynthesis; chemical ecology; natural products; secondary metabolism; structure elucidation; symbiosis; Introduction Although natural products represent the most consistently successful drug leads [1][2], many pharmaceutical

• studies also place the natural products into a genomic, regulatory, functional, and ecological context, and might allow drawing more general conclusions about the biosynthetic origins, the ecology and evolution of symbiotic associations. However, even in this ecological context natural product chemistry

My maize and blue brick road to physical organic chemistry in materials

• Anne J. McNeil

Beilstein J. Org. Chem. 2016, 12, 229–238, doi:10.3762/bjoc.12.24

• . Relationship between dissolution enthalpies and intermolecular interactions. Gelators exhibit (on average) larger ΔHdiss than nongelators, suggesting stronger solid-state interactions and weaker solvent interactions. Evolution of our design strategy for identifying new gelators. New gelator scaffolds

A journey in bioinspired supramolecular chemistry: from molecular tweezers to small molecules that target myotonic dystrophy

• Steven C. Zimmerman

Beilstein J. Org. Chem. 2016, 12, 125–138, doi:10.3762/bjoc.12.14

• therapeutic agents for myotonic dystrophy using a rational design approach that heavily relies on principles of supramolecular chemistry. How this work was influenced by that of others in the field and the evolution of each area of research is highlighted with selected examples. Keywords: catenanes

Versatile deprotonated NHC: C,N-bridged dinuclear iridium and rhodium complexes

• Albert Poater

Beilstein J. Org. Chem. 2016, 12, 117–124, doi:10.3762/bjoc.12.13

• nearly completely the geometry features for complexes 3–6. Bearing rhodium complex 3H-T is again more stable than 3H-H, even 0.2 kcal/mol more stable. To sum up, no change of behaviour between iridium and homologous rhodium complexes was observed. On the other hand, the evolution from H-T to H-H

• species. Steric maps confirm that the H-T is preferred since the metal centres are less sterically hindered, thus revealing the relatively unstable kinetic H-H isomers with respect to the H-T ones. However, screening the evolution from complex 3 to 6, going through complexes 4 and 5, the relative

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

• evolution of the CP intensity I(t) as a function of the contact time t [38]. The intensity behavior is dictated by two different time constants: TCH and T1ρ, the former affecting the initial part of the curve, the latter driving the final decay. When the two relaxation times deviate by at least two orders

Smart molecules for imaging, sensing and health (SMITH)

• Bradley D. Smith

Beilstein J. Org. Chem. 2015, 11, 2540–2548, doi:10.3762/bjoc.11.274

• and self-assembly processes that are crucial for cell growth and signaling. These precisely controlled association systems have been refined over billions of years of evolution. The selective recognition is driven by protein–protein interactions that operate at an interface with a surface area that is

N-Heterocyclic carbenes

• Steven P. Nolan

Beilstein J. Org. Chem. 2015, 11, 2474–2475, doi:10.3762/bjoc.11.268

• through detailed mechanistic work, which permits the design of ever-better performing catalytic systems. This design/mechanistic study/redesign cycle will ensure the continued evolution of the field. The area of NHC-based research is a worldwide effort, as exemplified by contributions in this NHC-focused

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

• boundary conditions (PBC). While MM methods involve energy minimizations of the simulated systems with respect to all the atomic coordinates, the MD methods describe the time evolution of the whole system at the chosen temperature, according to Newton’s equation of motion, thus following the kinetics of a

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

• ]. In the O2-rich environments in which it operates, this property makes RuBisCO a particularly inefficient biocatalyst and a major bottleneck to C3 carbon fixation. Through evolution, RuBisCO has adapted to rising oxygen concentrations by developing higher specifities for CO2 at the expense of

• overcome these limitations [74][75]. Though these studies have resulted in the recombinant expression of RuBisCO in useful hosts such as E. coli [75], development of improved selection systems for directed evolution [74], and further elucidation of RuBisCO properties [76], little progress has been made

• . Within this limited space, it appears that the various wild-type enzymes have been optimised through evolution to operate within their respective environments. Point-mutations in the protein itself are therefore unable to lead to great improvements in enzyme efficiency. A more promising strategy may be

Self-assemblies of γ-CDs with pentablock copolymers PMA-PPO-PEO-PPO-PMA and endcapping via atom transfer radical polymerization of 2-methacryloyloxyethyl phosphorylcholine

• Jing Lin,
• Tao Kong,
• Lin Ye,
• Ai-ying Zhang and
• Zeng-guo Feng

Beilstein J. Org. Chem. 2015, 11, 2267–2277, doi:10.3762/bjoc.11.247

• architecture of the resulting PPRs, the second in situ ATRP of 2-methacryloyloxyethyl phosphorylcholine (MPC) was conducted to endcap them into the same conformational PR-based multiblock copolymers. A schematic description on the self-assembly evolution of varying amounts of γ-CDs with PMA-PPO-PEO-PPO-PMA and

• matched the feed values, demonstrating the good inclusion complexation ability between γ-CD and pentablock polymers. As a typical example, the self-assembly evolution of PEP100M15CD is shown in Figure 1. When an aqueous solution of saturated γ-CD was mixed with a preset amount of PMA-PPO-PEO-PPO-PMA, the

• different polymer segments. Surprisingly, a white gel was formed after the turbid mixture was stored at 6–8 °C for at least 24 h. The turbidity evolution and hydrogel formation were observed in other PPR samples, except that PEP15CD was rapidly precipitated from the mixture. To endcap PPRs into PRs, the

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

• Abstract Kinetic experiments based on the measurement of nitrogen evolution in the reaction of ethyl diazoacetate (N2CHCO2Et, EDA) and styrene or methanol catalyzed by the [IPrAu]+ core (IPr = 1,3-bis(diisopropylphenyl)imidazole-2-ylidene) have provided evidence that the transfer of the carbene group

• section have provided the following statements: (i) there is only a slight effect of the nature of the substrate, styrene or methanol, in the rate of evolution of N2, and (ii) the reaction rate is affected by the relative substrate:catalyst ratio, both magnitudes being directly correlated. Scheme 5

• originates the immediate evolution of N2, the gold–carbene intermediate must form from 2 or 3. Also, this must be the rate determining step, efforts to detect such intermediates having proven unsuccessful. The commonly accepted pathway (route A, Scheme 5) would suppose an exchange of the substrate ligand

Olefin metathesis in air

• Lorenzo Piola,
• Fady Nahra and
• Steven P. Nolan

Beilstein J. Org. Chem. 2015, 11, 2038–2056, doi:10.3762/bjoc.11.221

• metathesis, the evolution of metathesis catalysts towards air stability has become an area of significant interest. In this fascinating area of study, beginning with early systems making use of high oxidation state early transition metal centers that required strict exclusion of water and air, advances have

• ][49][50]. To date, only one example is reported where catalyst 15 is used in air (see following section). Hoveyda–Grubbs catalyst The next notable evolution in terms of higher catalyst stability came from the Hoveyda group in 1999 [51]. While performing metathesis in the presence of isopropoxystyrene

Effective ascorbate-free and photolatent click reactions in water using a photoreducible copper(II)-ethylenediamine precatalyst

• Redouane Beniazza,
• Natalia Bayo,
• Florian Molton,
• Carole Duboc,
• Stéphane Massip,
• Nathan McClenaghan,
• Dominique Lastécouères and
• Jean-Marc Vincent

Beilstein J. Org. Chem. 2015, 11, 1950–1959, doi:10.3762/bjoc.11.211

• Cambridge Crystallographic Data Centre as deposition CCDC 1414149 for 4, and CCDC 1410011 for 1. Evolution of the UV–vis spectra of deaerated (freeze-pump-thaw degassed, sealed quartz cuvettes) THF (left) or water (right) solutions (3 mL) of complex 1 (2 mM) under irradiation at 365 nm using a TLC lamp

• placed at ≈1 cm from the cuvette. Evolution of the EPR spectra (X band, 298 K) of solutions of 1 under continuous irradiation (280–400 nm). A spectrum is recorded in the dark (black), then the light is switched on and the spectra (scanning time = 15 s) recorded during irradiation at times 0 s (blue), 50