Polyamine dendrimer

Fig. 8. Polyamine dendrimer of the fifth generation obtained on a kilogram scale...

Combinatorial approach to unsymmetrically tiered macromolecules [214] is a brand new area of research which would allow dendrimerization of materials (e. g., glass, classical polymers, fibers) and thus enable fine tuning of macromole-cular properties. For example, treatment of an amine terminated dendrimer with a mixture of complementary, isocyanate-based monomers [215, 216] affords a heterogeneous surfaced dendrimer. Selective transformation of the surface nitrile moieties via metal-catalyzed reduction to obtain a new polyamine dendrimer allows further combinatorial-based elaboration as illustrated in Fig. 42. 

Commercially available dendrimers are polyamine dendrimers (Astramol ,... 

Follow-on functionalisation with molecular moieties of biological importance, such as anti-tumour agents (e.g. 5-fluorouracil) currently appears particularly attractive. In this context, acetylation is particularly suitable as functionalisation reaction for oligo/polyamine dendrimers. It renders the dendrimers more water soluble, which is essential for biomedical applications [25]. The toxicity of den-... 

Fig. 3.13 Method of local bifunctionalisation of oligo-/polyamine dendrimers...

Monofunctionalisation of polyamine dendrimers with functionalised sulphonyl chlorides. 

Scheme 2 Syntheses of third-generation amidoferrocenyl [34-41] and pentamethylamido-ferrocenyl dendrimers [64,65] from the corresponding DSM polyamine dendrimer G3-dend-(NH2)i6- For analysis and comparison of their behavior as hosts of anions, see [64,65]...

Preparation of the amphipathic peptide modified cascade (38, Scheme 7.9) was facilitated by reaction of the polyamine dendrimer with /V-succinimidyl 3-(2-pyridinyldi-thio)propionate (SPDP 36) to give the polypyridinyldisulfide (37). Subsequent treatment of the pyridinyldisulfide moieties with the GALA peptide possessing a cysteine amino acid afforded the modified cascades (38). 

Using the principle of ion pair formation between ammonium cations and the phosphate anions of lipids, Matile et al.33 prepared 8, an amphiphilic polyamine dendrimer. Rather than acting as a membrane channel, 8 was expected to form reversible membrane defects in the lipid bilayer. The steroid moiety was expected to act as the hydrophobic anchor for bilayer orientation and steric bulk was expected to prevent the polyamine penetrating the bilayer. Proton transport was assessed in unilamellar vesicles using the pH-fluorescence technique in which the external pH was increased to 7.8 relative to the internal pH at 7.4. The results demonstrated that 8 was almost as active as gramicidin, and maximal flux was achieved in ca. 20 s. 

The structures of five protected functionalized isocyanate building blocks AP3-EP3 (94,95) are reported in Fig. 11.18, top. The protected side chains for each building block allowed further increase of ramification and loading (n —> 3n sites after an isocyanate coupling), but above all allowed a combinatorial deprotection/decoration strategy reported for a specific example in Fig. 11.18, bottom. The starting polyamine dendrimer 11.14 (32-PPl, schematically represented as in Fig. 11.18) (96) was treated with a stoichiometeric mixture of isocyanates DP3 and EP3 (0.5 eqs. each, step a. Fig. 

An example of a polyamine dendrimer functionalised by 2-pyridylethyl- substituents is (167).269 The interaction of (167) with copper(II) acceptors gives metal derivatives containing one metal for each bis[2-(2-pyridyl)ethyl]amine moiety. (167) is found to bind approximately 32 Cu ions. Polyamidoamine species containing Cu ions can be reduced in solution to zerovalent copper nanoclusters, providing a metal nanocomposite.270 Such copper(O) solutions are stable for several months, owing to the surface properties of the host dendrimer molecules. 

Figure 8. A polyamine dendrimer bearing planar-chiral cyclophane units (Vogtle et al.)...

Figure 10. Meijer et al. [53] have discovered the dendritic box , a fifth-generation polyamine dendrimer with bulky substituents, that can be used to include various types of guest molecules (amide hydrogen atoms have been omitted in the picture).

The variety of the examples listed above documents that dendrimer chemistry has attained increasing interest. In this compilation of recent results the trend towards functional and application-oriented molecules including biochemically active, photoswitchable, and polymerlike dendrimers is particularly apparent. Dendrimers cross the boundaries of classical organic chemistry and as new materials will penetrate deeper into the topical fields of nanostructures , supramolecules and polymers in the future. Increasing industrial research on dendrimers and the commercial availability of PAMAM and polyamine dendrimers should stimulate further investigations in this field. 

Commercially avaUahle dendrimers are polyamine dendrimers (Astramol, DSM) and poly(amidoamine) dendrimers (Starhurst, Dendritic Nanotechnologies)... 

Preparation of a Third Generation Polyamine Dendrimer Starting from Methyl... 

To a 1-liter flask equipped as in C above and containing 65.1 gm (0.757 mole) of methyl acrylate is added 28.4 gm (0.0272 mole) of the second generation polyamine dendrimer of D above dissolved in 84.6 gm of methanol over a 1.25 hr period. The resulting mixture is allowed to stand for 18 hr at room temperature (25°C) and then the excess methyl acrylate and methanol are removed under reduced pressure (2.0 mm Hg at 50°C) to yield 56.3 gm product (100% yield). 

Dendrimers can be reacted with a variety of compounds to further functionalize them to give them unique characteristics. For example, amine-terminated dendrimer can be reacted with imsaturated nitriles to give a polynitrile dendrimer. In another case the polyamine dendrimer can be reacted with jS-unsat-urated amides to give amide-terminated dendrimer. A whole host of possibilities can be visualized based on the reactivity of the amino group [43]. 

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