Branch cells construction

Figure 1.13 Overview of synthetic strategies for (a) branch cell construction, (b) dendron construction and (c) dendrimer construction annotated with discovery scientists...

PAMAM dendrimers are synthesized by the divergent approach. This methodology involves the in situ branch cell construction in stepwise, iterative stages (i.e. generation = 1, 2, 3. ..) around a desired core to produce mathemat-... 

Poly(amidoamine)-(PAMAM-Starburst)-Monodendrons Among the first Starburst (Cascade) syntheses we performed in the early 1980s [83] involved partially masked (differentiated) initiator cores. For example dodecyl-amine, hydroxyalkyl amines or partially protected alkylene diamines were used as initiator cores and submitted to sequential (a) Michael addition with methyl acrylate followed by (b) reaction with an excess of ethylene diamine to give in situ branch cell construction in a divergent manner. The resulting products were core functionalized monodendrons as shown below ... 

Figure 27.1 Hierarchy of empirical construction components (A) monomers, (B) branch cells, (C) dendrons and (D) dendrimers leading to (E) core-shell tecto(dendrimers)...

Time sequenced, step growth of branch cells and dendrimer structure Self replication of branch cells throughout dendrimer construction Structural proliferation of dendrimers with exponential amplification of branch cells" and surface functionality as a function of generation... 

Construction and control of branch cell segment lengths 1. 

Tam and co-workers [105-107] produced related dendrons on a Merrifield resin oilowed by surface functionalization with various antigenic polypeptide sequences. comparison of molar mass, number of terminal groups, and dimensions as a function of generation for the Denkewalter dendrons is shown in Table 1. Unlike ill the other dendron examples reported, the branch cells in this system are lnsymmetrical since they are constructed from unequal branchcell-segments as iescribed in Sect. 4.3.2. 

In a second dendritic series, Frechet et al. [117] selected 4,4-bis (4 -hydroxy-phenyl)pentanol 42 as the branch cell reagent unit for construction of a more flexible dendron. This synthetic sequence is illustrated in Scheme 13-1, 2. 

Fig. 22. Arylacetylenic branch cell reagent (A) suitable for the construction of arylacetylic mondendron (B)...

Fig. 24. Various oligonucleotide branch cell reagents [ A), (B), (C), (D)] suitable for constructing DNA/RNA dendrons and dendrimers...

Shinkai and coworkers (see Ref. 200) recently synthesized very fascinating azacrown ether linked dendrons by utilizing a branch cell reagent derived from 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane. These dendrons were constructed via the controlled convergent strategy and advanced to generation = 2. Tri-dendrons were constructed as described in Sect. 5.2.2.4. 

Divergent Initiator Core Method 5.23.1 In Situ Construction of Branch Cells... 

The reactive branch cell reagent tris(4-methoxymethylphenyl)phosphine (74) was used to construct dendrimers with up to 40 cationic sites within the infrastructure of the molecule. Simply advancing the valency of the central core phosphorous atom, produced tri-, and tetradendron dendrimers. In most of these poly(phosphonium) dendrimers, separate 31P-NMR signals for the core and peripheral phosphonium ion sites could be observed thus illustrating the hierarchial nature of the branch cells within these molecules. 

Dendritic macromolecules constructed from small-molecule monomers incorporate three major components a core, repeating branch cell units, and a corona or outer shell. The branch cells (BC), also known as repeating units (RU), are defined in terms of a branching angle. 

STRUCnjRE Dendrimers are three-dimensional macromolecules consisting of three major architectural components a core, branch cells, and terminal groups. These products are constructed from repeat units called branch cells [e.g.,... 

The conventional synthesis of dendrimers involves the divergent method, in which branch cells are constructed in situ arotmd the initiator core or preformed branch cells are attached to the core. Successive generations are then built. On the other hand, in the convergent method [131-133] the dendritic fragments are prepared by starting firom firag-... 

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