Incorporation of Functional Guest Molecules into an Internally Functionalizable Dendrimer through Olefin Metathesis

Internally Functionalized Dendrimers Based on Fully Substituted 1,2,3-Triazoles

Being one important class in dendrimer chemistry, internally functionalized dendrimers (IFDs) are still exiguous. Here we demonstrate the first construction of IFDs involving fully substituted 1,2,3-triazole rings as interior functionality carriers. Through divergent or convergent synthetic protocols established on the efficient iridium-catalyzed annulation of internal 1-thioalkynes with organic azides (IrAAC), sequence-controlled heterolayered dendrimers with different branched structures are achieved in a convenient manner. ¹ H NMR, MS and SEC characterizations well identify their architecture and high purity. This article is protected by copyright. All rights reserved.

Chiral Imidazolidin-4-one with catalytic amount of Dicationic ionic liquid act as a recoverable and reusable Organocatalyst for asymmetric Diels-Alder reaction

Imidazolidin-4-one is used as a recoverable organocatalyst for the asymmetric Diels-Alder reaction in the presence of catalytic amount of dicationic ionic liquid and trifluoroacetic acid as a co-catalyst. The Diels-Alder reaction between model substrate cyclopentadiene and crotonaldehyde gave the product in 95% conversion and 87% ee of the endo-product. The catalyst was shown better reusability when the 20 mol% of dicationic ionic liquid was used and catalyst was reused upto 5 cycles, conversion remains upto 3 recycles but ee of endo-9 was slightly droped.

Convergent dendrimer synthesis by olefin metathesis and studies toward glycoconjugation

The synthesis of novel hyperbranched monodisperse linear dendrimers, based on 2,2-bis-(hydroxymethyl)-propionic acid (bis-MPA), has been achieved by convergent metathesis-mediated coupling between the alkene-terminated focal point of bis-MPA dendrons. On their surface, dendrimers present 4, 8 and 16 functional groups. Glycodendrimers exposing multiple saccharide moieties have also been obtained. To the best of our knowledge, this is the first example of the use of metathesis for focal point coupling.

Olefin cross metathesis and ring-closing metathesis in polymer chemistry

The use of olefin cross metathesis in preparing functional polymers, through either pre-functionalisation of monomers or post-polymerisation functionalisation is growing in both scope and breadth, as discussed in this review article.

Magnetic Fe3O4 nanoparticles supporting Macmillan with controlled shell structure as an efficient and reusable catalyst for asymmetric reaction

Magnetic nanoparticles grafted with chiral polymer brushes offer an effective way to bridge the gap between heterogeneous and homogeneous catalysis.

Synthesis of MacMillan catalyst modified with ionic liquid as a recoverable catalyst for asymmetric Diels–Alder reaction

MacMillan catalyst was modified with imidazolium ionic liquid by ester linkage and acts as recoverable and reusable catalyst for asymmetric Diels–Alder reactions.

An emerging interface between life science and nanotechnology: present status and prospects of reproductive healthcare aided by nano-biotechnology

Among the various applications of nano-biotechnology, healthcare is considered one of the most significant domains. For that possibility to synthesize various kind of nanoparticles (NPs) and the ever-increasing ability to control their size as well as structure, to improve surface characteristics and binding NPs with other desired curing agents has played an important role. In this paper, a brief sketch of various kinds of nanomaterials and their biomedical applications is given. Despite claims of bio-nanotechnology about to touch all areas of medical science, information pertaining to the role of nanotechnology for the betterment of reproductive healthcare is indeed limited. Therefore, the various achievements of nano-biotechnology for healthcare in general have been illustrated while giving special insight into the role of nano-biotechnology for the future of reproductive healthcare betterment as well as current achievements of nanoscience and nanotechnology in this arena.

Strain-promoted alkyne azide cycloaddition for the functionalization of poly(amide)-based dendrons and dendrimers

Functionalization of a poly(amido)-based dendron with ethylene glycol chains (PEG) using copper-catalyzed alkyne azide cycloaddition (CuAAC) afforded dendrons with significant levels of copper contaminations, preventing the use of such materials for biological applications. We suggest that the presence of amide, PEG, and triazole functional groups allows for copper complexation, thereby preventing the separation of the copper catalyst from the final dendron. To minimize this problem, synthetic variations on CuAAC including the addition of "click" additives for copper sequestering as well as the use of copper wire as the copper source were investigated. None of these strategies, however, resulted in copper-free products. In contrast, we developed a copper-free strain-promoted alkyne azide cycloaddition (SPAAC) strategy that functionalized poly(amide)-based dendrons and dendrimers with PEG chains quantitatively under mild reaction conditions without any metal contamination. The SPAAC products were characterized by (1)H and (13)C NMR, 2D HSQC and COSY NMR, mass spectrometry, and elemental analysis. This is the first report on the use of SPAAC for dendrimer functionalization, and the results obtained here show that SPAAC is an important tool to the dendrimer and more general biomaterials community for the functionalization of macromolecular structures due to the mild and metal-free reaction conditions, no side products, tolerance toward functional groups, and high yields.

Amino acid-functionalized dendrimers with heterobifunctional chemoselective peripheral groups for drug delivery applications

Dendrimers have emerged as multifunctional carriers for targeted drug delivery, gene delivery and imaging. Improving the functional versatility at the surface for carrying multiple conjugation reactions is becoming vital. Typically, generation four polyamidoamine (G4-PAMAM) dendrimers bear approximately 64 symmetrical end groups, often requiring different spacers to conjugate various functional groups (drugs and targeting moities), increasing the synthetic steps. In the present study, a simple one-step synthesis to convert each symmetrical end group of G4-PAMAM dendrimers into two reactive, distinct orthogonal and chemoselective groups is described. A near-complete end-capping of the dendrimers (87-93%) with amino acids results in heterobifunctional G4-PAMAM dendrimers bearing a very high (> or = 110) diverse peripheral end groups (OH+NHBoc, OH+COOMe, SH+NHBoc, and COOH+NHBoc). Postfunctionalization ability of these dendrimers was evaluated. The heterobifunctional groups at the dendrimer periphery could be chemoselectively conjugated to multiple moities such as drugs (indomethacin and dexamethasone) and drugs and imaging agents (dexamethasone and FITC). These conjugations could be achieved in immediate succession without functional group conversions, eliminating the additional elaborate synthetic steps traditionally required to append specific linkers. Furthermore, one of the two functional handles at periphery was used to develop in situ forming hydrogels, whereas the other handle could be used for conjugating the drugs (e.g., dexamethasone). The heterobifunctional dendrimers with either "NH(2) or SH (thiopyridyl protected form)" terminations showed in situ hydrogel formation by cross-linking with N-hydroxysuccinimide or thiol-terminated multiarm polyethylene glycol (20 kDa). The choice of amino acids as versatile linkers would enable biocompatible dendrimer scaffolds for use in drug delivery. Zeta-potential measurements showed drastic lowering of the charge on G4-PAMAM-NH(2) dendrimers by end-capping with amino acids, whereas in the case of neutral G4-PAMAM-OH dendrimers, the charge did not increase or decrease substantially. The in vitro cytotoxicity and hemolysis assay showed that the heterobifunctional dendrimers were noncytotoxic in the 100 ng/mL to 1 mg/mL concentration range. With this study, we demonstrate the development of biocompatible dendrimers bearing multiple orthogonal surface groups, enabling the attachment of drugs, imaging agents, and gel formation using minimal synthetic steps.

Bifunctional dendrimers: from robust synthesis and accelerated one-pot postfunctionalization strategy to potential applications

A fourth wheel: Two sets of bifunctional AB(2)C dendrimers having internal acetylene/azides and external hydroxy groups were constructed utilizing benign synthetic protocols. An in situ postfunctionalization strategy was successfully carried out to illustrate the chemoselective nature of these dendrimers. The dendrimers were also transformed into dendritic nanoparticles or utilized as dendritic crosslinkers for the fabrication hydrogels.