scholarly journals Domino ring-opening–ring-closing enyne metathesis vs enyne metathesis of norbornene derivatives with alkynyl side chains. Construction of condensed polycarbocycles

2018 ◽  
Vol 14 ◽  
pp. 2708-2714 ◽  
Author(s):  
Ritabrata Datta ◽  
Subrata Ghosh
Keyword(s):  
Ring Opening ◽  
Functional Group ◽  
Domino Reaction ◽  
Side Chain ◽  
Side Chains ◽  
Enyne Metathesis ◽  
Substrate Structure ◽  
Norbornene Derivatives

The metathesis of norbornene derivatives with alkynyl side-chain with Grubbs’ ruthenium alkylidine as catalyst has been investigated with the objective of constructing condensed polycyclic structures. This investigation demonstrated that the generally observed domino reaction course involving a ring-opening metathesis of the norbornene unit and a ring-closing enyne metathesis is influenced to a great extent by the nature of the functional group and the substrate structure and may follow a different reaction course than what is usually observed. In cases where ROM–RCEYM occurred, the resulting 1,3-diene reacts in situ with the dienophile to provide condensed tetracyclic systems.

Highly photoluminescent poly(norbornene)s carrying platinum-acetylide complex moieties in the side chain: evaluation of oxygen sensing and TTA–UC

2021 ◽  
Author(s):  
Taichi Sotani ◽  
Toshiko Mizokuro ◽  
Tatsuo Yajima ◽  
Hiromitsu Sogawa ◽  
Fumio Sanda
Keyword(s):  
Ring Opening ◽  
Oxygen Sensing ◽  
Polymeric Materials ◽  
Side Chain ◽  
Thermally Stable ◽  
Ring Opening Metathesis Polymerization ◽  
Metathesis Polymerization ◽  
Norbornene Derivatives

Ring-opening metathesis polymerization (ROMP) of norbornene derivatives is useful for preparing thermally stable and transparent polymeric materials with good moldability. This study deals with ROMP of norbornene monomer 1 bearing...

Diversifying Polyhydroxyalkanoates – End-Group and Side-Chain Functionality

2017 ◽  
Vol 14 (6) ◽  
pp. 757-767 ◽  
Author(s):  
Michal Michalak ◽  
Iwona Kwiecien ◽  
Michal Kwiecien ◽  
Grazyna Adamus ◽  
Karin Odelius ◽  
...  
Keyword(s):  
Functional Groups ◽  
Polymer Chain ◽  
Ring Opening ◽  
Functional Group ◽  
Side Chain ◽  
Natural Origin ◽  
Polymer Formation ◽  
End Groups ◽  
Group Diversity ◽  
End Group

Background: Polyhydroxyalkanoates (PHAs) are a natural origin biodegradable polyesters consisted of various 3- and 4-hydroxyacid derived repeating units produced by microorganisms as energy storage. PHAs have been intensively studied due to their biodegradability and biocompatibility enabling their use both in packaging and agriculture as well as in medicine and pharmacy. PHAs obtained via biotechnological routes can possess various functional groups in their side chains. However, the diversity in their functionality is limited due to issues of conservation of functional groups during the polymer formation. Objective: The review focuses on recent progress in the area of synthesis of PHAs functionalized with various reactive as well as bioactive end and side groups. Conclusion: A potent route to resolve the problem of functional group diversity in natural origin PHAs involves post-polymerization modification, where the desired side groups can be created. On the contrary, synthetically produced PHA analogs obtained directly via ring-opening polymerization of β-lactones offer various functionalities at different position throughout the polymer chain. The desired α- and ω-end groups can be introduced into the polymer chain using specific polymerization, initiation or termination strategies, respectively. The preferred side chain functionality is obtained by choosing the appropriate β-lactone monomers bearing respective functional groups. All functional groups may also be subjected to additional chemical modification. The degradation of PHA as a method for producing functional polymers as well as their possible further applications are also discussed.

Mesophase and Optical Properties of Side Chain Copolyacrylate with Mesogens and OLLA Segments Side Chains

2011 ◽  
Vol 181-182 ◽  
pp. 397-400
Author(s):  
Ya Ping Liu ◽  
Zhuo Hua Li ◽  
Ling Min Sun ◽  
Run Tao Dong ◽  
Hong Ru Chen ◽  
...  
Keyword(s):  
Ring Opening ◽  
Optical Rotation ◽  
Helical Structure ◽  
Ring Opening Polymerization ◽  
Side Chain ◽  
Side Chains ◽  
Induce Effect ◽  
Phase Structures ◽  
Acrylate Esters ◽  
Phase Behaviors

Thermal properties and phase behaviors of series of newly synthesized copolyacrylate esters with oligomeric-L-LA (OLLA) segments (DP = 10-40) and mesogens as side chains were characterized. The OLLAs prepared by ring opening polymerization of L-LA with active HO-group were modified to form polymerizable acrylate esters and then copolymerized with polymerizable mesogens. The thermal behaviors of these copolyacrylate esters were studied by DSC and POM measurements and phase structures by XRD measurements. The mesogens showed very good induce effect on the formation of layered structures. CD measurements were used to determine the helical structure and the optical rotation power of the side chain copolyacrylate esters.

Hierarchical superstructures of norbornene-based polymers depending on dendronized side-chains

2016 ◽  
Vol 7 (33) ◽  
pp. 5304-5311 ◽  
Author(s):  
Dae-Yoon Kim ◽  
Dong-Gue Kang ◽  
Suyong Shin ◽  
Tae-Lim Choi ◽  
Kwang-Un Jeong
Keyword(s):  
Self Assembly ◽  
Ring Opening ◽  
Main Chain ◽  
The Self ◽  
Side Chain ◽  
Side Chains ◽  
Ring Opening Metathesis Polymerization ◽  
Metathesis Polymerization ◽  
Main Chain Polymers

For understanding the self-assembly behaviours of norbornene-based main-chain polymers depending on side-chain pendants, a series of polynorbornenes containing the programmed dendrons is newly designed and successfully synthesized via ring opening metathesis polymerization.

The Synthesis of the Dimer and Trimer Ether-Linked Components of Hematoporphyrin Derivative

1990 ◽  
Vol 43 (11) ◽  
pp. 1889 ◽  
Author(s):  
CJ Byrne ◽  
IK Morris ◽  
AD Ward
Keyword(s):  
Spectral Properties ◽  
Hydrogen Bromide ◽  
Coupling Reaction ◽  
Side Chain ◽  
Side Chains ◽  
Hematoporphyrin Derivative ◽  
Acetyl Group ◽  
Porphyrin Dimer

The preparation is described of all of the likely dimer and trimer ether-linked components of the anticancer material known as hematoporphyrin derivative. The hydroxyethyl side chain of one porphyrin, related to hematoporphyrin, reacts readily with a bromoethyl system derived from the same, or similar, hematoporphyrin -derived porphyrin to form a diporphyrin ether. The coupling reaction can be controlled to occur in situ, allowing the preparation of a symmetrical ether-linked dimer , or separately to provide an asymmetrically substituted porphyrin dimer . The bromoethyl groups can be formed from either the hydroxyethyl groups or, more slowly, from a vinyl side chain by using hydrogen bromide in dichloromethane. Ether-linked porphyrin trimers can be prepared by reacting a dibromoethyl system with 2 equiv. of a hydroxyethyl -containing porphyrin or by further reaction of an initially formed dimer. Hydroxyethyl side chains in the dimers and trimers are best obtained by reduction of an acetyl group. Some spectral properties of the products are described.

scholarly journals Dioxygen Activation with Molybdenum Complexes Bearing Amide-Functionalized Iminophenolate Ligands

Molecules ◽  
2019 ◽  
Vol 24 (9) ◽  
pp. 1814 ◽  
Author(s):  
Niklas Zwettler ◽  
Madeleine A. Ehweiner ◽  
Jörg A. Schachner ◽  
Antoine Dupé ◽  
Ferdinand Belaj ◽  
...  
Keyword(s):  
General Structure ◽  
Aerobic Oxidation ◽  
Molecular Structures ◽  
Side Chain ◽  
Side Chains ◽  
X Ray Diffraction ◽  
Subsequent Reaction ◽  
Internal Hydrogen ◽  
Internal Hydrogen Bond

Two novel iminophenolate ligands with amidopropyl side chains (HL2 and HL3) on the imine functionality have been synthesized in order to prepare dioxidomolybdenum(VI) complexes of the general structure [MoO2L2] featuring pendant internal hydrogen bond donors. For reasons of comparison, a previously published complex featuring n-butyl side chains (L1) was included in the investigation. Three complexes (1–3) obtained using these ligands (HL1–HL3) were able to activate dioxygen in an in situ approach: The intermediate molybdenum(IV) species [MoO(PMe3)L2] is first generated by treatment with an excess of PMe3. Subsequent reaction with dioxygen leads to oxido peroxido complexes of the structure [MoO(O2)L2]. For the complex employing the ligand with the n-butyl side chain, the isolation of the oxidomolybdenum(IV) phosphino complex [MoO(PMe3)(L1)2] (4) was successful, whereas the respective Mo(IV) species employing the ligands with the amidopropyl side chains were found to be not stable enough to be isolated. The three oxido peroxido complexes of the structure [MoO(O2)L2] (9–11) were systematically compared to assess the influence of internal hydrogen bonds on the geometry as well as the catalytic activity in aerobic oxidation. All complexes were characterized by spectroscopic means. Furthermore, molecular structures were determined by single-crystal X-ray diffraction analyses of HL3, 1–3, 9–11 together with three polynuclear products {[MoO(L2)2]2(µ-O)} (7), {[MoO(L2)]4(µ-O)6} (8) and [C9H13N2O]4[Mo8O26]·6OPMe3 (12) which were obtained during the synthesis of reduced complexes of the type [MoO(PMe3)L2] (4–6).

Influence of Flexible Side-Chains on the Breathing Phase Transition of Pillared Layer MOFs: A Force Field Investigation

2020 ◽  
Author(s):  
Julian Keupp ◽  
Johannes P. Dürholt ◽  
Rochus Schmid
Keyword(s):  
First Principles ◽  
Good Accuracy ◽  
Field Investigation ◽  
Square Lattice ◽  
Side Chain ◽  
Second Step ◽  
Side Chains ◽  
Dynamics Simulations ◽  
Complex Phenomena ◽  
Closed Pore

The prototypical pillared layer MOFs, formed by a square lattice of paddle-<br>wheel units and connected by dinitrogen pillars, can undergo a breathing phase<br>transition by a “wine-rack” type motion of the square lattice. We studied this not<br>yet fully understood behavior using an accurate first principles parameterized force<br>field (MOF-FF) for larger nanocrystallites on the example of Zn 2 (bdc) 2 (dabco) [bdc:<br>benzenedicarboxylate, dabco: (1,4-diazabicyclo[2.2.2]octane)] and found clear indi-<br>cations for an interface between a closed and an open pore phase traveling through<br>the system during the phase transformation [Adv. Theory Simul. 2019, 2, 11]. In<br>conventional simulations in small supercells this mechanism is prevented by periodic<br>boundary conditions (PBC), enforcing a synchronous transformation of the entire<br>crystal. Here, we extend this investigation to pillared layer MOFs with flexible<br>side-chains, attached to the linker. Such functionalized (fu-)MOFs are experimen-<br>tally known to have different properties with the side-chains acting as fixed guest<br>molecules. First, in order to extend the parameterization for such flexible groups,<br>1a new parametrization strategy for MOF-FF had to be developed, using a multi-<br>structure force based fit method. The resulting parametrization for a library of<br>fu-MOFs is then validated with respect to a set of reference systems and shows very<br>good accuracy. In the second step, a series of fu-MOFs with increasing side-chain<br>length is studied with respect to the influence of the side-chains on the breathing<br>behavior. For small supercells in PBC a systematic trend of the closed pore volume<br>with the chain length is observed. However, for a nanocrystallite model a distinct<br>interface between a closed and an open pore phase is visible only for the short chain<br>length, whereas for longer chains the interface broadens and a nearly concerted trans-<br>formation is observed. Only by molecular dynamics simulations using accurate force<br>fields such complex phenomena can be studied on a molecular level.

The Total Synthesis of Rhabdastrellic Acid A

2018 ◽  
Author(s):  
Yaroslav Boyko ◽  
Christopher Huck ◽  
David Sarlah
Keyword(s):  
Total Synthesis ◽  
Late Stage ◽  
Cross Coupling ◽  
Side Chains ◽  
General Strategy ◽  
Modular Approach ◽  
Linear Sequence ◽  
Generating Sequence ◽  
First Time

<div>The first total synthesis of rhabdastrellic acid A, a highly cytotoxic isomalabaricane triterpenoid, has been accomplished in a linear sequence of 14 steps from commercial geranylacetone. The prominently strained <i>trans-syn-trans</i>-perhydrobenz[<i>e</i>]indene core characteristic of the isomalabaricanes is efficiently accessed in a selective manner for the first time through a rapid, complexity-generating sequence incorporating a reductive radical polyene cyclization, an unprecedented oxidative Rautenstrauch cycloisomerization, and umpolung 𝛼-substitution of a <i>p</i>-toluenesulfonylhydrazone with in situ reductive transposition. A late-stage cross-coupling in concert with a modular approach to polyunsaturated side chains renders this a general strategy for the synthesis of numerous family members of these synthetically challenging and hitherto inaccessible marine triterpenoids.</div>

scholarly journals Effects of Amino Acid Side-Chain Length and Chemical Structure on Anionic Polyglutamic and Polyaspartic Acid Cellulose-Based Polyelectrolyte Brushes

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1789
Author(s):  
Dmitry Tolmachev ◽  
George Mamistvalov ◽  
Natalia Lukasheva ◽  
Sergey Larin ◽  
Mikko Karttunen
Keyword(s):  
Glutamic Acid ◽  
Chain Length ◽  
Chemical Structure ◽  
Side Chain ◽  
Side Chains ◽  
Side Chain Length ◽  
Polyelectrolyte Brushes ◽  
Grafting Density ◽  
The Difference ◽  
Cellulose Surface

We used atomistic molecular dynamics (MD) simulations to study polyelectrolyte brushes based on anionic α,L-glutamic acid and α,L-aspartic acid grafted on cellulose in the presence of divalent CaCl2 salt at different concentrations. The motivation is to search for ways to control properties such as sorption capacity and the structural response of the brush to multivalent salts. For this detailed understanding of the role of side-chain length, the chemical structure and their interplay are required. It was found that in the case of glutamic acid oligomers, the longer side chains facilitate attractive interactions with the cellulose surface, which forces the grafted chains to lie down on the surface. The additional methylene group in the side chain enables side-chain rotation, enhancing this effect. On the other hand, the shorter and more restricted side chains of aspartic acid oligomers prevent attractive interactions to a large degree and push the grafted chains away from the surface. The difference in side-chain length also leads to differences in other properties of the brush in divalent salt solutions. At a low grafting density, the longer side chains of glutamic acid allow the adsorbed cations to be spatially distributed inside the brush resulting in a charge inversion. With an increase in grafting density, the difference in the total charge of the aspartic and glutamine brushes disappears, but new structural features appear. The longer sides allow for ion bridging between the grafted chains and the cellulose surface without a significant change in main-chain conformation. This leads to the brush structure being less sensitive to changes in salt concentration.

scholarly journals Unusual Structural Features in the Adduct of Dirhodium Tetraacetate with Lysozyme

2021 ◽  
Vol 22 (3) ◽  
pp. 1496
Author(s):  
Domenico Loreto ◽  
Giarita Ferraro ◽  
Antonello Merlino
Keyword(s):  
Anticancer Agents ◽  
Structural Features ◽  
Side Chain ◽  
Side Chains ◽  
Valuable Insight ◽  
Experimental Conditions ◽  
Egg White Lysozyme ◽  
Potential Applications ◽  
Model Protein ◽  
Hen Egg White

The structures of the adducts formed upon reaction of the cytotoxic paddlewheel dirhodium complex [Rh2(μ-O2CCH3)4] with the model protein hen egg white lysozyme (HEWL) under different experimental conditions are reported. Results indicate that [Rh2(μ-O2CCH3)4] extensively reacts with HEWL:it in part breaks down, at variance with what happens in reactions with other proteins. A Rh center coordinates the side chains of Arg14 and His15. Dimeric Rh–Rh units with Rh–Rh distances between 2.3 and 2.5 Å are bound to the side chains of Asp18, Asp101, Asn93, and Lys96, while a dirhodium unit with a Rh–Rh distance of 3.2–3.4 Å binds the C-terminal carboxylate and the side chain of Lys13 at the interface between two symmetry-related molecules. An additional monometallic fragment binds the side chain of Lys33. These data, which are supported by replicated structural determinations, shed light on the reactivity of dirhodium tetracarboxylates with proteins, providing useful information for the design of new Rh-containing biomaterials with an array of potential applications in the field of catalysis or of medicinal chemistry and valuable insight into the mechanism of action of these potential anticancer agents.

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