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Itaru Hamachi - One of the best experts on this subject based on the ideXlab platform.

  • Design of peptide-based bolaamphiphiles exhibiting heat-set hydrogelation via Retro-Diels–Alder Reaction
    Journal of materials chemistry. B, 2014
    Co-Authors: Rika Ochi, Masato Ikeda, Takashi Nishida, Itaru Hamachi
    Abstract:

    Supramolecular hydrogels have attracted much attention as smart soft materials. To install various stimuli-responsive functions in the supramolecular hydrogels, skilful utility of chemical Reactions for triggering the change in molecular structure of hydrogelators or their precursor in response to external stimuli is a promising strategy. We have recently developed a unique heat-set supramolecular hydrogel, which was triggered by rationally designed molecular conversion of a glycolipid-based bolaamphiphile into a hydrogelator via Retro-Diels–Alder Reaction. Here we designed new bolaamphiphiles based on short peptide-based hydrogelators as a scaffold to accelerate the heat-set hydrogelation process and also demonstrated the flexible molecular design of such bolaamphiphiles.

  • heat induced morphological transformation of supramolecular nanostructures by Retro diels alder Reaction
    Chemistry: A European Journal, 2012
    Co-Authors: Masato Ikeda, Rika Ochi, Darrin J. Pochan, Yushi Kurita, Itaru Hamachi
    Abstract:

    Controlling the morphology of supramolecular nanostructures in response to external stimuli is an important challenge in the development of functional soft materials. Here we show that a morphological transformation from 2D nanosheets to a network of 1D nanofibers is triggered by heating, which induces molecular conversion of a bolaamphiphile to a hydrogelator by means of a Retro-Diels-Alder Reaction, thereby producing a new heat-set supramolecular hydrogel. We anticipate that our design will be a starting point for more sophisticated supramolecular systems that integrate the thermodynamics of molecular assembly and the kinetics of chemical Reactions to create complex supramolecular nanostructures.

  • Heat‐Induced Morphological Transformation of Supramolecular Nanostructures by Retro‐Diels–Alder Reaction
    Chemistry (Weinheim an der Bergstrasse Germany), 2012
    Co-Authors: Masato Ikeda, Rika Ochi, Yu‐shi Kurita, Darrin J. Pochan, Itaru Hamachi
    Abstract:

    Controlling the morphology of supramolecular nanostructures in response to external stimuli is an important challenge in the development of functional soft materials. Here we show that a morphological transformation from 2D nanosheets to a network of 1D nanofibers is triggered by heating, which induces molecular conversion of a bolaamphiphile to a hydrogelator by means of a Retro-Diels-Alder Reaction, thereby producing a new heat-set supramolecular hydrogel. We anticipate that our design will be a starting point for more sophisticated supramolecular systems that integrate the thermodynamics of molecular assembly and the kinetics of chemical Reactions to create complex supramolecular nanostructures.

Masato Ikeda - One of the best experts on this subject based on the ideXlab platform.

  • Design of peptide-based bolaamphiphiles exhibiting heat-set hydrogelation via Retro-Diels–Alder Reaction
    Journal of materials chemistry. B, 2014
    Co-Authors: Rika Ochi, Masato Ikeda, Takashi Nishida, Itaru Hamachi
    Abstract:

    Supramolecular hydrogels have attracted much attention as smart soft materials. To install various stimuli-responsive functions in the supramolecular hydrogels, skilful utility of chemical Reactions for triggering the change in molecular structure of hydrogelators or their precursor in response to external stimuli is a promising strategy. We have recently developed a unique heat-set supramolecular hydrogel, which was triggered by rationally designed molecular conversion of a glycolipid-based bolaamphiphile into a hydrogelator via Retro-Diels–Alder Reaction. Here we designed new bolaamphiphiles based on short peptide-based hydrogelators as a scaffold to accelerate the heat-set hydrogelation process and also demonstrated the flexible molecular design of such bolaamphiphiles.

  • heat induced morphological transformation of supramolecular nanostructures by Retro diels alder Reaction
    Chemistry: A European Journal, 2012
    Co-Authors: Masato Ikeda, Rika Ochi, Darrin J. Pochan, Yushi Kurita, Itaru Hamachi
    Abstract:

    Controlling the morphology of supramolecular nanostructures in response to external stimuli is an important challenge in the development of functional soft materials. Here we show that a morphological transformation from 2D nanosheets to a network of 1D nanofibers is triggered by heating, which induces molecular conversion of a bolaamphiphile to a hydrogelator by means of a Retro-Diels-Alder Reaction, thereby producing a new heat-set supramolecular hydrogel. We anticipate that our design will be a starting point for more sophisticated supramolecular systems that integrate the thermodynamics of molecular assembly and the kinetics of chemical Reactions to create complex supramolecular nanostructures.

  • Heat‐Induced Morphological Transformation of Supramolecular Nanostructures by Retro‐Diels–Alder Reaction
    Chemistry (Weinheim an der Bergstrasse Germany), 2012
    Co-Authors: Masato Ikeda, Rika Ochi, Yu‐shi Kurita, Darrin J. Pochan, Itaru Hamachi
    Abstract:

    Controlling the morphology of supramolecular nanostructures in response to external stimuli is an important challenge in the development of functional soft materials. Here we show that a morphological transformation from 2D nanosheets to a network of 1D nanofibers is triggered by heating, which induces molecular conversion of a bolaamphiphile to a hydrogelator by means of a Retro-Diels-Alder Reaction, thereby producing a new heat-set supramolecular hydrogel. We anticipate that our design will be a starting point for more sophisticated supramolecular systems that integrate the thermodynamics of molecular assembly and the kinetics of chemical Reactions to create complex supramolecular nanostructures.

Ferenc Fulop - One of the best experts on this subject based on the ideXlab platform.

  • Continuous-flow Retro-Diels-Alder Reaction: an efficient method for the preparation of pyrimidinone derivatives.
    Beilstein journal of organic chemistry, 2018
    Co-Authors: Imane Nekkaa, Marta Palko, Istvan M Mandity, Ferenc Fulop
    Abstract:

    The syntheses of various pyrimidinones as potentially bioactive products by means of the highly controlled continuous-flow Retro-Diels-Alder Reaction of condensed pyrimidinone derivatives are presented. Noteworthy, the use of this approach allowed us to rapidly screen a selection of conditions and quickly confirm the viability of preparing the desired pyrimidinones in short Reaction times. Yields typically higher than those published earlier using conventional batch or microwave processes were achieved.

  • a domino ring closure followed by Retro diels alder Reaction for the preparation of pyrimido 2 1 a isoindole enantiomers
    European Journal of Organic Chemistry, 2016
    Co-Authors: Beata Fekete, Marta Palko, Istvan M Mandity, Matti Haukka, Ferenc Fulop
    Abstract:

    A simple method was developed to prepare pyrimido[2,1-a]isoindole derivatives by using di-endo- and di-exo-ethyl 3-aminobicyclo[2.2.1]hept-5-ene-2-carboxylate enantiomers as chiral sources. The method is based on a domino ring-closure Reaction of norbornene 2-aminohydroxamic acid followed by microwave-induced Retro-Diels–Alder Reaction. In the case of enantiomeric starting substances, the chirality is transferred from norbornene derivatives to pyrimido[2,1-a]isoindoles. The configurations of the synthesized compounds were determined by 1D and 2D NMR spectroscopy [based on 2D NOE cross-peaks and 3JH,H coupling constants] and X-ray crystallography.

  • A Domino Ring-Closure Followed by Retro-Diels–Alder Reaction for the Preparation of Pyrimido[2,1-a]isoindole Enantiomers
    European Journal of Organic Chemistry, 2016
    Co-Authors: Beata Fekete, Marta Palko, Istvan M Mandity, Matti Haukka, Ferenc Fulop
    Abstract:

    A simple method was developed to prepare pyrimido[2,1-a]isoindole derivatives by using di-endo- and di-exo-ethyl 3-aminobicyclo[2.2.1]hept-5-ene-2-carboxylate enantiomers as chiral sources. The method is based on a domino ring-closure Reaction of norbornene 2-aminohydroxamic acid followed by microwave-induced Retro-Diels–Alder Reaction. In the case of enantiomeric starting substances, the chirality is transferred from norbornene derivatives to pyrimido[2,1-a]isoindoles. The configurations of the synthesized compounds were determined by 1D and 2D NMR spectroscopy [based on 2D NOE cross-peaks and 3JH,H coupling constants] and X-ray crystallography.

Jonathan M. White - One of the best experts on this subject based on the ideXlab platform.

  • Applying the Structure Correlation Principle to Retro Diels Alder Reactions
    Acta Crystallographica Section A Foundations and Advances, 2014
    Co-Authors: Brett R. Pool, Rachel Goh, Jesse Roth-barton, Jonathan M. White
    Abstract:

    The early stages of molecular rearrangements are often apparent in the crystal structures of molecules susceptible to that rearrangement. For example, if a particular bond is broken, or if a particular group migrates during the rearrangement, then deviations of bond distances and angles from their `standard values' along the Reaction coordinate are often observed. This is the structure correlation principle,1 which holds provided the molecule exists in the ground state, in a geometry, which is similar to the transition state geometry for the Reaction. In this geometry the frontier orbitals whose interactions facilitate the Reaction, can mix in the ground state. This paper discusses the application of this principle to pericyclic fragmentation Reactions related to the Retro Diels Alder Reaction, using low temperature X-ray structural analysis of a range of model substrates. The substrates can be classified on the basis of this data into three groups: (i) those that undergo a synchronous Retro Diels Alder Reaction, (2) those that undergo an asynchronous Retro Diels Alder Reaction, and (3) those that react via a 2-step process. Examples of molecules falling into these three categories are given below.

  • Structure Correlation Study of Some Diels–Alder Cycloadducts of Anthracene
    Australian Journal of Chemistry, 2009
    Co-Authors: Yit Wooi Goh, Jonathan M. White
    Abstract:

    Crystal structures of some Diels–Alder cycloadducts of anthracene and a variety of dienophiles reveal structural effects consistent with the manifestation of the early stages of the Retro Diels–Alder Reaction in the ground state structure. The symmetrical cycloadducts 3 and 4 reveal a qualitative relationship between structure and reactivity, whereas the cycloadducts of 9-methoxyanthracene show structural effects suggestive of the early stages of an asynchronous Retro Diels–Alder Reaction.

  • Structural Investigations into the Retro-Diels-Alder Reaction. Experimental and Theoretical Studies.
    Journal of the American Chemical Society, 2002
    Co-Authors: David M. Birney, Brett R. Pool, Tang Kuan Lim, Joanne H. P. Koh, Jonathan M. White
    Abstract:

    The manifestations of the Retro-Diels Alder Reaction in the ground-state structures of a range of cyclopentadiene and cyclohexadiene cycloadducts 9−15 have been investigated by a combination of techniques. These include low-temperature X-ray crystallography, density functional calculations (B3LYP/6-31G(d,p)) on both the ground states and transition states, and the measurement of 13C−13C coupling constants. We have found that the carbon−carbon bonds (labeled bonds a and b), which break in the rDA, are longer in the cycloadducts 9−15 than in their corresponding saturated analogues 9s−15s, which cannot undergo the rDA Reaction. The degree of carbon−carbon bond lengthening appears to be related to the reactivity of the cycloadduct, thus the more reactive benzoquinone cycloadducts 5b and 13 have longer carbon−carbon bonds. Those cycloadducts 14 and 15 which are predicted to undergo asynchronous Reactions show differing degrees of carbon−carbon bond lengthening, reflecting the differing degrees of bond breaking...

  • Structural Manifestations of the Retro Diels−Alder Reaction
    Organic letters, 2000
    Co-Authors: Brett R. Pool, Jonathan M. White
    Abstract:

    Examination of selected cyclohexene derivatives which are fixed into the boat conformation reveals structural deviations from “normal” C−C bond distances consistent with the early stages of the Retro Diels−Alder Reaction.

Shriniwas D Samant - One of the best experts on this subject based on the ideXlab platform.