Synthesis and Self-assembly of Amphiphilic Hetero-arm Molecular Brushes

2011 ◽  
Vol 64 (8) ◽  
pp. 1100 ◽  
Author(s):  
Waled Hadasha ◽  
Mpho Mothunya ◽  
Niels Akeroyd ◽  
Bert Klumperman
Keyword(s):  
Self Assembly ◽  
Ring Opening ◽  
Alkyl Chain ◽  
Ring Closure ◽  
Molecular Brushes ◽  
Alkyl Amines ◽  
Ring Opening Reaction ◽  
Grafting From ◽  
Chain Lengths

We report the synthesis of amphiphilic hetero-arm molecular brushes (AMBs), which were prepared by a combination of ‘grafting from’ and ‘grafting onto’ methodologies. First, styrene-terminated polyethylene glycol macromonomer (VB-PEG12, ∼666 g mol–1) was copolymerized with maleic anhydride (MAnh) to yield a polymer containing hydrophilic PEG chains and reactive (MAnh) groups. Subsequently, the reactive MAnh units in the obtained polymer were modified via a ring-opening reaction using primary alkyl amines, with different alkyl chain lengths, as the nucleophile. In situ ring closure yielded the styrene–maleimide-based AMB. The amphiphilic character of the AMBs was used for their self-assembly in different solvents. The effect of the ratio in hydrophilic to hydrophobic graft length on the morphology of the assemblies was studied using scanning electron microscopy.

First Total Synthesis of a Fluorinated Calystegin

2010 ◽  
Vol 65 (4) ◽  
pp. 445-451 ◽  
Author(s):  
René Csuk ◽  
Erik Prell ◽  
Stefan Reißmann ◽  
Claudia Korb
Keyword(s):  
Total Synthesis ◽  
Ring Opening ◽  
Competitive Inhibitor ◽  
Ring Closure ◽  
Target Compound ◽  
Metathesis Reaction ◽  
Grubbs Catalyst ◽  
Ring Opening Reaction ◽  
Ultrasound Assisted ◽  
Key Steps

A straightforward chiral pool synthesis for the first fluorinated calystegin is described. Key steps of this synthesis include an ultrasound-assisted Zn-mediated tandem ring opening reaction followed by a Grubbs’ catalyst-mediated ring closure metathesis reaction. The target compound is a selective and competitive inhibitor for a β -glycosidase.

Preparation and Characterization of Zein-Based Nanoparticles via Ring-Opening Reaction and Self-Assembly as Aqueous Nanocarriers for Pesticides

2020 ◽  
Vol 68 (36) ◽  
pp. 9624-9635
Author(s):  
Li Hao ◽  
Guanquan Lin ◽  
Haoguang Wang ◽  
Chuanggeng Wei ◽  
Long Chen ◽  
...  
Keyword(s):  
Self Assembly ◽  
Ring Opening ◽  
Ring Opening Reaction

Thermal intramolecular reactions of Δ1-1,2,4-triazolines with extended exocyclic unsaturation

1988 ◽  
Vol 66 (3) ◽  
pp. 385-390 ◽  
Author(s):  
Adrian L. Schwan ◽  
John Warkentin
Keyword(s):  
Ring Opening ◽  
Hydrolysis Product ◽  
Sigmatropic Rearrangement ◽  
Membered Ring ◽  
Ring Closure ◽  
Experimental Results ◽  
First Order ◽  
Ring Opening Reaction ◽  
Intramolecular Reactions

Fumaratotriazoline (1) and amidotriazoline (3) undergo thermal first-order transformations in solution at 65 °C. The former affords the isomeric pyrrole 5 and its hydrolysis product 6. A mechanism involving opening of the initial five-membered ring to form 8, followed by closure to a new five-membered ring (9), is proposed. Amidotriazoline (3) loses N2 on heating to form 19. The experimental results are best accommodated in terms of a novel mechanism involving an electrocyclic ring closure, a [3 + 2] cycloreversion to form an ylide, a sigmatropic rearrangement of the ylide, and, finally, an electrocyclic ring-opening reaction.

Growth of Double-Chained Cationic Surfactant Films on Mica

2006 ◽  
Vol 59 (6) ◽  
pp. 381 ◽  
Author(s):  
Annabelle Blom ◽  
Gregory G. Warr ◽  
Erica J. Wanless
Keyword(s):  
Atomic Force Microscopy ◽  
Alkyl Chain ◽  
Effect Of Temperature ◽  
Equilibration Time ◽  
Force Microscopy ◽  
Atomic Force ◽  
The Difference ◽  
Chain Lengths ◽  
Gel Transition

The evolution of adsorbed dialkyl chained quaternary ammonium surfactant films with different alkyl chain lengths has been observed in situ using atomic force microscopy (AFM). Both di-C12DAB and di-C14DAB form a cohesive bilayer immediately, which is observed to strengthen with equilibration time. The slow equilibrium of di-C16DAB allows examination of the film at less than saturated coverage and reveals growth of the bilayer through the nucleation and coalescence of patches. The difference in height between higher and lower regions is insufficient for bilayer and monolayer regions and the postulated structure is that of regions of bilayer with different packing densities. The effect of temperature on film morphologies near the gel transition is also examined.

Enantioselective ring opening of tropinone. A new entry into tropane alkaloids

1997 ◽  
Vol 75 (6) ◽  
pp. 754-761 ◽  
Author(s):  
Marek Majewski ◽  
Ryszard Lazny ◽  
Agnieszka Ulaczyk
Keyword(s):  
Ring Opening ◽  
Stereoselective Synthesis ◽  
Tropane Alkaloids ◽  
Amine Hydrochloride ◽  
Lithium Amides ◽  
Ring Opening Reaction ◽  
Alkyl Chloroformates ◽  
Optically Pure ◽  
Enantioselective Deprotonation

The lithium enolate of tropinone reacts with alkyl chloroformates to give 6-N-carboalkoxy-N-methyl-2-cycloheptenones (4). These compounds can be produced enantioselectively, in up to 95% ee, if chiral lithium amides (derived from optically pure amines 5–7) are used for deprotonation of tropinone in the presence of additives. The effect of additives such as LiCl, LiBr, LiF, LiClO4, CeCl3, ZnCl2, LiOH, TMEDA, HMPA, and DMPU on enantioselectivity of this deprotonation–ring opening sequence varies from slight to very large depending on the chiral amide – additive combination. Especially large increases in enantioselectivity are observed when the chiral, C2 symmetrical, lithium bis-α,α′-methylbenzylamide (Li-5a) is used with one equivalent of LiCl. This reagent is best generated in situ from the corresponding amine hydrochloride and n-BuLi (2 equiv.). The ring-opening reaction combined with transposition of the carbonyl group (via Wharton reaction or allylic oxidation) provides a new method of stereoselective synthesis of tropane alkaloids having a protected hydroxyl at C-6 or C-7 (6β- and 7β-acetoxytropanes 14a, b) and physoperuvine (19). Keywords: enantioselective deprotonation, tropane alkaloids.

Intermediates from ring-opening reactions. Reactions of 2-chloro-5-nitropyridine and 2-chloro-3-nitropyridine with deuteroxide ion in selected solvents

1984 ◽  
Vol 62 (6) ◽  
pp. 1120-1123 ◽  
Author(s):  
John D. Reinheimer ◽  
Nicolas Sourbatis ◽  
Robert L. Lavallee ◽  
Douglas Goodwin ◽  
George L. Gould
Keyword(s):  
Ring Opening ◽  
Pyridine Ring ◽  
Ring Closure ◽  
Polar Solvents ◽  
Open Chain ◽  
Decomposition Products ◽  
Aqueous Sodium ◽  
Ring Opening Reaction ◽  
Ring Opening Reactions ◽  
Kinetics Of

Open chain intermediates from the ring-opening reaction of aqueous sodium deuteroxide (2 mol) with 2-chloro-5-nitropyridine (1 mol) and 2-chloro-3-nitropyridine (1 mol) were isolated. These intermediates were purified, analyzed for elemental composition, and characterized by various spectrophotometric techniques. The intermediate formed from 2-chloro-5-nitropyridine and two equivalents of deuteroxide ion reacts with additional deuteroxide in D2O in various polar solvents to reclose the pyridine ring. The kinetics of the ring closure reaction are reported and are supplemented with observations of salt and solvent effects upon the rate of closure. In addition, a mechanism for the ring closure is presented. The intermediate formed from 2-chloro-3-nitropyridine did not undergo a similar ring closure when reacted with additional deuteroxide, but instead formed various decomposition products. A reason for the failure of this ring closure is suggested.

scholarly journals Photoresponsive supramolecular coordination polyelectrolyte as smart anticounterfeiting inks

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Zhiqiang Li ◽  
Xiao Liu ◽  
Guannan Wang ◽  
Bin Li ◽  
Hongzhong Chen ◽  
...  
Keyword(s):  
Self Assembly ◽  
Ring Opening ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Ring Closure ◽  
New Class ◽  
Supramolecular Coordination ◽  
Ligand Coordination ◽  
Information Patterns ◽  
New Generation

AbstractWhile photoluminescence printing is a widely applied anticounterfeiting technique, there are still challenges in developing new generation anticounterfeiting materials with high security. Here we report the construction of a photoresponsive supramolecular coordination polyelectrolyte (SCP) through hierarchical self-assembly of lanthanide ion, bis-ligand and diarylethene unit, driven by metal-ligand coordination and ionic interaction. Owing to the conformation-dependent photochromic fluorescence resonance energy transfer between the lanthanide donor and diarylethene acceptor, the ring-closure/ring-opening isomerization of the diarylethene unit leads to a photoreversible luminescence on/off switch in the SCP. The SCP is then utilized as security ink to print various patterns, through which photoreversible multiple information patterns with visible/invisible transformations are realized by simply alternating the irradiation with UV and visible light. This work demonstrates the possibility of developing a new class of smart anticounterfeiting materials, which could be operated in a noninvasive manner with a higher level of security.

scholarly journals PhSeZnCl in the Synthesis of Steroidal β-Hydroxy-Phenylselenides Having Antibacterial Activity

2019 ◽  
Vol 20 (9) ◽  
pp. 2121 ◽  
Author(s):  
Jastrzebska ◽  
Mellea ◽  
Salerno ◽  
Grzes ◽  
Siergiejczyk ◽  
...  
Keyword(s):  
Antibacterial Activity ◽  
Biofilm Formation ◽  
Ring Opening ◽  
Antibacterial Properties ◽  
Multidrug Resistant ◽  
Bacterial Biofilm ◽  
Resistant Bacteria ◽  
Multidrug Resistant Bacteria ◽  
Ring Opening Reaction

We report here the reaction of in situ prepared PhSeZnCl with steroid derivatives having an epoxide as an electrophilic functionalization. The corresponding ring-opening reaction resulted to be regio- and stereoselective affording to novel phenylselenium-substituted steroids. Assessment of their antibacterial properties against multidrug-resistant bacteria, such as Pseudomonas aeruginosa Xen 5 strain, indicates an interesting bactericidal activity and their ability to prevent bacterial biofilm formation.

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