9 research outputs found
Self-interrupted synthesis of sterically hindered aliphatic polyamide dendrimers
Hydrolytically and enzymatically stable nanoscale synthetic constructs, with well-defined structures that exhibit antimicrobial activity, offer exciting possibilities for diverse applications in the emerging field of nanomedicine. Herein, we demonstrate that it is the core conformation, rather than periodicity, that ultimately controls the synthesis of sterically hindered aliphatic polyamide dendrimers. The latter self-interrupt at a predictable low generation number due to backfolding of their peripheral groups, which in turn leads to well-defined nanoarchitectures
Synthesis of 뱉Aminonitriles with Benzimidazolic and Theophyllinic Backbones Using the Strecker Reaction
An example of the
application of the Strecker reaction in the synthesis
of a new class of α-aminonitriles with benzimidazole and theophylline
backbones has been developed. For the synthesis of these compounds,
first 4-hydroxybenzaldehyde was reacted with 1,3- and 1,5-dibromides/epibromohydrin
to produce the corresponding bromo-substituted aldehydes. Then, benzimidazole/theophylline
was reacted with the latter to generate the related benzimidazolic/theophyllinic
aldehydes. Finally, the Strecker reactions of the synthetic benzimidazolic
and theophyllinic aldehydes with different amines afforded the target
products
Asymmetric fluorination reactions promoted by chiral hydrogen bondingâbased organocatalysts
Fluorinated compounds can exhibit interesting biological properties. The importance of these species has made that the chemistry of fluorine has experienced a great development. On this review, the recent advances on asymmetric fluorination reactions promoted by chiral hydrogen bondingâbased organocatalysts are discussed. Hence, examples using phosphoric acid, carboxylic acid, (thio)urea and squaramide derivatives are illustrated. The growth of this field is amazing. We have only considered pivotal works in which direct fluorination takes place using a fluorinating agent, leaving aside the reactions where a fluorine atom is incorporated from the beginning as part of other reactants. Herein, the scarce existing examples on this field of research have been compiled.The authors thank Ministerio de EconomĂa, Industria y Competitividad (MINECOâFEDER CTQ2016â75816âC2â1âP, CTQ2017â88091âP and PID2019â104379RBâC21) and Gobierno de AragĂłnâFondo Social Europeo (Research Group E07_20R) for financial support of our research.Peer reviewe
Silica Sulfuric Acid (SSA) as a Highly Efficient Heterogeneous Catalyst for Persilylation of Purine and Pyrimidine Nucleobases and Other N
Self-interrupted synthesis of sterically hindered aliphatic polyamide dendrimers
2,2-Bis(azidomethyl)propionic acid was prepared in four steps and 85% yield from the commercially available 2,2-bis(hydroxymethyl) propionic acid and used as the starting building block for the divergent, convergent, and double-stage convergent-divergent iterative methods for the synthesis of dendrimers and dendrons containing ethylenediamine (EDA), piperazine (PPZ), and methyl 2,2- bis(aminomethyl)propionate (COOMe) cores. These cores have the same multiplicity but different conformations. A diversity of synthetic methods were used for the synthesis of dendrimers and dendrons. Regardless of the method used, a self-interruption of the synthesis was observed at generation 4 for the dendrimer with an EDA core and at generation 5 for the one with a PPZ core, whereas for the COOMe core, self-interruption was observed at generation 6 dendron, which is equivalent to generation 5 dendrimer. Molecular modeling and molecular-dynamics simulations demonstrated that the observed self-interruption is determined by the backfolding of the azide groups at the periphery of the dendrimer. The latter conformation inhibits completely the heterogeneous hydrogenation of the azide groups catalyzed by 10% Pd/carbon as well as homogeneous hydrogenation by the Staudinger method. These self-terminated polyamide dendrimers are enzymatically and hydrolytically stable and also exhibit antimicrobial activity. Thus, these nanoscale constructs open avenues for biomedical applications
Self-interrupted synthesis of sterically hindered aliphatic polyamide dendrimers
2,2-Bis(azidomethyl)propionic acid was prepared in four steps and 85% yield from the commercially available 2,2-bis(hydroxymethyl)propionic acid and used as the starting building block for the divergent, convergent, and double-stage convergentâdivergent iterative methods for the synthesis of dendrimers and dendrons containing ethylenediamine (EDA), piperazine (PPZ), and methyl 2,2-bis(aminomethyl)propionate (COOMe) cores. These cores have the same multiplicity but different conformations. A diversity of synthetic methods were used for the synthesis of dendrimers and dendrons. Regardless of the method used, a self-interruption of the synthesis was observed at generation 4 for the dendrimer with an EDA core and at generation 5 for the one with a PPZ core, whereas for the COOMe core, self-interruption was observed at generation 6 dendron, which is equivalent to generation 5 dendrimer. Molecular modeling and molecular-dynamics simulations demonstrated that the observed self-interruption is determined by the backfolding of the azide groups at the periphery of the dendrimer. The latter conformation inhibits completely the heterogeneous hydrogenation of the azide groups catalyzed by 10% Pd/carbon as well as homogeneous hydrogenation by the Staudinger method. These self-terminated polyamide dendrimers are enzymatically and hydrolytically stable and also exhibit antimicrobial activity. Thus, these nanoscale constructs open avenues for biomedical applications