Amine-terminated derivative

Another approach uses reactive alkyl halogen compounds containing a terminal carboxylate group on the other end to form spacer arms off the dextran polymer from each available hydroxyl. In this manner, Brunswick et al. (1988) used chloroacetic acid to modify the hydroxyl groups to form the carboxymethyl derivative. The carboxylates then were aminated with ethylene diamine to create an amine-terminal derivative (Inman, 1985). Finally, the amines were modified with iodoacetate to form a sulfhydryl-reactive polymer (Figure 25.14). 

Several chemical approaches may be used to form the amine- or carboxyl-terminal dextran derivative. The simplest procedure may be to prepare polyaldehyde dextran according to the procedure of Section 2.1, and then make the spacer arm derivative by reductively animating an amine-containing organic compound onto it. For instance, short diamine compounds such as ethylene diamine or diaminodipropylamine (3,3 -iminotepropylamine) can be coupled in excess to polyaldehyde dextran to create an amine-terminal derivative. Carboxyl-terminal derivatives may be prepared similarly by coupling molecules such as 6-aminocaproic acid or p-alanine to polyaldehyde... 

Figure 388 An amine terminal derivative of dextran may be prepared through a two-step process involving the reaction of chloroacetic acid with the hydroxyl groups of the polymer to create carboxylates. Next, ethylene diamine is coupled using a carbodiimide-mediated reaction to give the primary amine functional groups.

Studies of metal ion binding [Cu(II), Ni(II), Fe(III), Mn(II), Ag(I), Au(III), Pd(II), Pt(II), Ru(III)] by different OH- and NHj-terminated PAMAM derivatives in aqueous solution show that these metal ions are bound to the branching tertiary amine functions with high capacity, with the observed uptake clearly dependent on the number of generations and on the pH. In the case of amine-terminated derivatives, the metal ions can also bind to these end groups, resulting in a further increase in uptake [8]. 

Acylation reactions can be done at the nucleophilic sites on pyrimidines using activated forms of carboxylic acids. Acylation of functional groups in nucleotides typically is used for protection during synthesis (Reese, 1973). However, for bioconjugate applications, the reactivity of native groups on pyrimidines is not as great as that obtained using an amine-terminal spacer derivative, such as those described in Chapter 27, Section 2.1. Yields and reaction rates are typically low for direct acylation or alkylation of pyrimidine bases, especially in aqueous environments. 

Dextran derivatives containing carboxyl- or amine-terminal spacer arms may be prepared by a number of techniques. These derivatives are useful for coupling amine- or carboxylate-containing molecules through a carbodiimide-mediated reaction to form an amide bond (Chapter 3, Section 1). Amine-terminal spacers also can be used to create secondary reactive groups by modification with a heterobifunctional crosslinking agent (Chapter 5). 

In a somewhat similar scheme, Noguchi et al. (1992) prepared a carboxylate spacer arm by reacting 6-bromohexanoic acid with a dextran polymer. The carboxylate then was aminated with ethylene diamine to form an amine-terminal spacer (Figure 25.15). This dextran derivative finally was reacted with N-Succinimidyl 3-(2-pyridyldithio)propionate (SPDP) (Chapter 5, Section 1.1) to create the desired sulfhydryl-reactive polymer (Section 2.4, this chapter). The SPDP-activated polymer then could be used to prepare an immunoconjugate composed of an antibody against human colon cancer conjugated with the drug mitomycin-C. 

Figure 27.4 Reaction of guanine bases with N-bromosuccinimide causes bromination at the C-8 position of the ring. Amine nucleophiles can be coupled to this active derivative by nucleophilic displacement. Reaction of diamine compounds results in amine-terminal spacers that can be further modified to contain detectable components.

Figure 27.5 Oligonucleotides containing a 5 -phosphate group can be reacted with EDC in the presence of imidazole to form an active phosphorimidazolide intermediate. This derivative is highly reactive with amine nucleophiles, forming a phosphoramidate linkage. Diamines reacted with the phosphorimidazolide result in amine-terminal spacers that can be modified with detectable components.

The uniformity of these hyperbranched PAA grafts on PE films was studied by forming derivatives with visible and fluorescent dyes. These hyperbranched films were modified by treating an activated 3-PAA/PE film with an amine terminated p-methyl red dye (MR) 9 or with a dansyl amine 10 to form MR/3-PAA/PE or dansyl/3-PAA/PE films, respectively. Visual inspection under a light or fluorescence microscope showed that the methyl red-labeled and fluorescently labeled films were uniform in color and fluorescence. The methyl red/3-PAA/PE film derivafive showed a responsive color change wifh change in pH. The MR labeled 3-PAA/PE film was red after immersion in an acidic ethanol solution and yellow after treatment with a basic ethanol solution. 

Hirao, et al., 3411 have described a very useful method for the animation of living anionic polymers. Polymeric anions were reacted with a trimethylsilyl derivative of an aldimine ( >) which generated the primary amine-terminated polymers after quenching with dilute acid (Eq. (83)). 

Noguchi et al. (1992) used an amine-terminal spacer arm derivative of dextran to react with SPDP (Chapter 5, Section 1.1) in the creation of a pyridyldisulfide-activated polymer (Fig. 391). Brunswick etal. (1988) used a different amine-terminal spacer arm derivative of dextran and subsequently coupled iodoacetate to form a sulfhydryl-reactive polymer (Fig. 392). Heindel et al. (1991) used a unique approach. They... 

Reaction of various primary amine-terminated dendrimers with either inorganic or organic acids allows the preparation of a wide variety of crystalline derivatives. One such intermediate was implicated in the development of lyotropic phases [156] when octanoic acid was combined with Starburst poly(ethylenimine) (generation-3). 

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