Polyamidoamine ethylenediamine core

A bifunctional ligand was attached to different generation of ethylenediamine cored polyamidoamine dendrimer (PAMAM). Then Gl, G2 or G4 PAMAM dendrimer (8, 16 or 64 terminal primary amines) were mixed in water with an equimolecular amount of DOaAP 295c per number of primary amine (Scheme 62). Gd(III) and Gd(III)/Y(lll) complexes were prepared by mixing 2 equiv. of metal cation per thiourea function and removing the excess by washing with disodium EDTA [226, 227]. The reaction was extended to the fourth... 

Eig. 33. Ethylenediamine-core polyamidoamine-dendrimers 96 and 97. Redrawn, with permission, after Kobayashi... 

The first true dendrimers were the polyamidoamines (PAMAMs). They are also known as starburst dendrimers, and the term starburst is a trademark of the Dow Chemical Company, who have commercialized these materials for a range of applications. These dendrimers use ammonia as the core molecule, and this is reacted with methyl acrylate in the presence of methanol, after which ethylenediamine is added. This is shown in Scheme 9.2. 

The divergent method is illustrated in Fig. 2-22 for the synthesis of polyamidoamine (PAMAM) dendrimers [Tomalia et al., 1990]. A repetitive sequence of two reactions are used—the Michael addition of an amine to an a,P-unsaturated ester followed by nucleophilic substitution of ester by amine. Ammonia is the starting core molecule. The first step involves reaction of ammonia with excess methyl acrylate (MA) to form LXIII followed by reaction with excess ethylenediamine (EDA) to yield LXIV. LXV is a schematic representation of the dendrimer formed after four more repetitive sequences of MA and EDA. 

Starburst polyamidoamine (PAMAM) synthesis [2, 77-81, 83] may begin with either a nucleophilic or an electrophilic core. In the case of nucleophilic cores such as ammonia or amine, step A in Scheme 21 involves exhaustive Michael addition to methyl acrylate. This addition occurs very rapidly and in high yield with essentially complete selectively and no amidation at room temperature. Step B requires addition of this triester intermediate to a large excess of ethylenediamine at room temperature to produce the terminal triamine core cell shown in Fig. 2 and Scheme 21. Repeating the sequence of steps A and B leads, via a hexaester... 

The poly(imine) dendrimers form a special type of polymer. The dendrimers have different physical properties from linear polymers, and some have been used for biomedical applications. Dendrimers typically start with a core molecule. Ammonia can be used for this purpose. In the presence of methanol, ammonia reacts with methyl acrylate forming N(CH2CH2COOCH3)3. The resulting molecule can react further with ethylenediamine or other diamines forming N(CH2CH2CONHCH2CH2NH2)3- At the end of each branch is a free amino group that can react with two methyl acrylate monomers and further with two ethylenediamine molecules. The continuation of the process leads to a dendrimer (polyamidoamine or PAMAM) [2]. A different dendrimer is poly(propylene imine), which has butylenediamine as a core molecule. 

---