| 1. |
- Caraballo, Rémi, 1982-
(författare)
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Dynamic Sulfur Chemistry : Screening, Evaluation and Catalysis
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with the design, formation and evaluation of dynamic systems constructed by means of sulfur-containing reversible reactions, in organic and aqueous media and under mild conditions. In a first part, the synthesis of thioglycoside derivatives, constituting the biologically relevant starting components of the dynamic systems, is described. In addition, the pD-profile of the mutarotation process in aqueous media for a series of 1-thioaldoses is reported and revealed an astonishing beta-anomeric preference for all the carbohydrate analogs under acidic or neutral conditions. In a second part, the phosphine-catalyzed or -mediated disulfide metathesis for dynamic system generation in organic or aqueous media is presented, respectively. The direct in situ 1H STD-NMR resolution of a dynamic carbohydrate system in the presence of a target protein (Concanavalin A) proved the suitability and compatibility of such disulfide metathesis protocols for the discovery of biologically relevant ligands. In a third part, hemithioacetal formation is demonstrated as a new and efficient reversible reaction for the spontaneous generation of a dynamic system, despite a virtual character of the component associations in basic aqueous media. The direct in situ 1H STD-NMR identification of the best dynamic beta-galactosidase inhibitors from the dynamic HTA system was performed and the results were confirmed by inhibition studies. Thus, the HTA product formed from the reaction between 1-thiogalactopyranose and a pyridine carboxaldehyde derivative provided the best dynamic inhibitor. In a fourth and final part, a dynamic drug design strategy, where the best inhibitors from the aforementioned dynamic HTA system were used as model for the design of non-dynamic (or “static”) beta-galactosidase inhibitors, is depicted. Inhibition studies disclosed potent leads among the set of ligands.
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| 2. |
- Vongvilai, Pornrapee, 1978-
(författare)
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Dynamic Covalent Resolution: Applications in System Screening and Asymmetric Synthesis
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Combined thermodynamic/kinetic events amount to a kinetically controlled Dynamic Combinatorial Resolution (DCR) process, where the lability of themolecules/aggregates are used to generate dynamics, and the species experiencing the lowest activation energy is selected via kinetic process. Bothinter- and intramolecular processes can be performed using this concept,resulting in complete resolution and associated amplification of the selected species. When intermolecular processes are resolved using this method, an additional advantage is that only a catalytic amount of selector is required tocontrol the system.In this thesis, the Henry and Strecker reactions were developed as efficient C–C bond-forming routes to single and multi-level dynamic covalent systems.These methods efficiently provided a vast variety of substrates from smallnumbers of starting compounds. These dynamic systems, generated underthermodynamic control at mild conditions, were coupled in one-pot processes with kinetically controlled lipase-mediated transacylation. The enzym emediated resolution of the dynamic nitroaldol system led to enantiomericallypure β-nitroacetates in high yield. Furthermore, combination of multi-leveldynamic Strecker systems and lipase-mediated acylation resulted in theresolution of specific α-aminonitriles from the pool.In addition, the asymmetric synthesis of discrete β-nitroalkanol derivatives wassimply achieved, resulting in high yields and high enantiomeric purities through the direct one-pot procedure. Moreover, racemase type activity oflipase enzyme through N-substituted α-aminonitrile structure has been discovered. By use of control experiments together with molecular modeling,the mechanism of the racemization process has been established. Asymmetric synthesis of N-methyl α-aminonitriles was also performed through the dualfunction of lipase, resulting in high yield and good enantio selectivity.
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| 3. |
- Dunér, Gunnar, et al.
(författare)
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Surface-confined photopolymerization of pH-responsive acrylamide/acrylate brushes on polymer thin films
- 2008
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 24:14, s. 7559-7564
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Tidskriftsartikel (refereegranskat)abstract
- Dynamic acrylamide/acrylate polymeric brushes were synthesized at gold-plated quartz crystal surfaces. The crystals were initially coated with polystyrene-type thin films, derivatized with photolabile iniferter groups, and subsequently subjected to photoinitiated polymerization in acrylamide/acrylate monomer feeds. This surface-confined polymerization method enabled direct photocontrol over the polymerization, as followed by increased frequency responses of the crystal oscillations in a quartz crystal microbalance (QCM). The produced polymer layers were also found to be highly sensitive to external acid/base stimuli. Large oscillation frequency shifts were detected when the brushes were exposed to buffer solutions of different pH. The dynamic behavior of the resulting polymeric brushes was evaluated, and the extent of expansion and contraction of the films was monitored by the QCM setup in situ in real time. The resulting responses were rapid, and the effects were fully reversible. Low pH resulted in full contractions of the films, whereas higher pH yielded maximal expansion in order to minimize repulsion around the charged acrylate centers. The surfaces also proved to be very robust because the responsiveness was reproducible over many cycles of repeated expansion and contraction. Using ellipsometry, copolymer layers were estimated to be similar to 220 nm in a collapsed state and similar to 340 nm in the expanded state, effectively increasing the thickness of the film by 55%.
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| 4. |
- REN, Yansong
(författare)
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Dynamic Chemistry for Asymmetric Synthesis, Molecular Motion and Constitutional Exchange
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Living matter is built on complex dynamic systems consisting of numerus biotransformations. By exploiting the adaptive and evolutive behaviors ofmolecular matter, dynamic chemistry has developed as an important tool tounderstand the organization of nonliving matter into complex living systems.This thesis concerns three aspects of dynamic chemistry with a general focus onthe influence of different stimuli on the structures and functions of dynamicsystems.The first section focuses on dynamic kinetic resolution, where enzymes areutilized for asymmetric synthesis of an enantiopure (2R,5R)-1,3-oxathiolane. Byemploying surfactant-treated subtilisin Carlsberg and Candida antarcticalipase B, the absolute configuration of the resulting 1,3-oxathiolane ring couldbe efficiently controlled.The second section addresses the motional dynamics of configurational enamineswitch systems controlled by multiple stimuli. Complete forward and backwardrotation around the enamine C=C bond could be precisely regulated uponaddition of acid/base or metal ions. The enamine switches exhibited specificsensing ability for CuII ions in solution. Moreover, the enamines exhibitedswitchable aggregation-induced emission in the solid state, which could beapplied in the development of sensors as well as fluorescent organogel.Lastly, the enamine switches could readily undergo constitutional exchange withprimary amines under catalytic acidic conditions, resulting in dynamic enaminesystems. However, under basic conditions or in the presence of excessive acid,this process exhibited extremely slow kinetics, leading to an efficient regulationof the exchange process by controlling the switch status with regulation of pHin the system.
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| 5. |
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| 6. |
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| 7. |
- Neranon, Kitjanit, 1985-, et al.
(författare)
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Design, Synthesis and Self-Assembly of Functional Amphiphilic Metallodendrimers
- 2020
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Ingår i: ChemistryOpen. - : John Wiley & Sons. - 2191-1363. ; 9:1, s. 45-52
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Tidskriftsartikel (refereegranskat)abstract
- A new family of alkynylated, amphiphilic dendrimers consisting of amidoamine linkers connected to 5,5 '-functionalized 2,2 '-bipyridine cores has been developed and evaluated in the formation of metallodendrimers of different generations and in self-assembly protocols. A convergent synthetic strategy was applied to provide dumbbell-shaped amphiphilic dendrimers, where the 2,2 '-bipyridine cores could be coordinated to Fe-II centers to afford corresponding metallodendrimers. The ability of the metallic- and non-metallic dendritic structures to self-assemble into functional supramolecular aggregates were furthermore evaluated in aqueous solution. Spherical aggregates with sizes of a few hundred nanometers were generally produced, where controlled disassembly of the metallodendrimers through decomplexation could be achieved.
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| 8. |
- Schaufelberger, Fredrik, et al.
(författare)
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Hydrogen-Bond Catalysis of Imine Exchange in Dynamic Covalent Systems
- 2020
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Ingår i: Chemistry - A European Journal. - : John Wiley & Sons. - 0947-6539 .- 1521-3765. ; 26:67, s. 15581-15588
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Tidskriftsartikel (refereegranskat)abstract
- The reversibility of imine bonds has been exploited to great effect in the field of dynamic covalent chemistry, with applications such as preparation of functional systems, dynamic materials, molecular machines, and covalent organic frameworks. However, acid catalysis is commonly needed for efficient equilibration of imine mixtures. Herein, it is demonstrated that hydrogen bond donors such as thioureas and squaramides can catalyze the equilibration of dynamic imine systems under unprecedentedly mild conditions. Catalysis occurs in a range of solvents and in the presence of many sensitive additives, showing moderate to good rate accelerations for both imine metathesis and transimination with amines, hydrazines, and hydroxylamines. Furthermore, the catalyst proved simple to immobilize, introducing both reusability and extended control of the equilibration process.
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| 9. |
- Xie, Sheng, et al.
(författare)
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Impact of Hydrogen Bonding on the Fluorescence of N-Amidinated Fluoroquinolones
- 2019
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Ingår i: Chemistry - An Asian Journal. - : Wiley-Blackwell. - 1861-4728 .- 1861-471X. ; 14:6, s. 910-916
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Tidskriftsartikel (refereegranskat)abstract
- The fluorescence properties of AIE-active N-amidinated fluoroquinolones, efficiently obtained by a perfluoroaryl azide-aldehyde-amine reaction, have been studied. The fluorophores were discovered to elicit a highly sensitive fluorescence quenching response towards guest molecules with hydrogen-bond-donating ability. This effect was evaluated in a range of protic/aprotic solvents with different H-bonding capabilities, and also in aqueous media. The influence of acid/base was furthermore addressed. The hydrogen-bonding interactions were studied by IR, NMR, UV/Vis and time-resolved fluorescence decay, revealing their roles in quenching of the fluorescence emission. Due to the pronounced quenching property of water, the N-amidinated fluoroquinolones could be utilized as fluorescent probes for quantifying trace amount of water in organic solvents.
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| 10. |
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