Graft active ester method

Carboxyethyl derivatives of the nucleic acid bases were grafted onto poly-L-lysine by using the activated ester method ( ). 

The poly-L-lysine derivatives containing pendant nucleic add bases can be prepared alternatively by using a polymer modification reaction69 (Scheme 19). Carboxyethyl derivatives of the bases were grafted onto poly-L-lysine by using the activated ester method . Poly-L-lysine was allowed to react in this case as trifluoroacetate71. ... 

Acenaphthalene 119-122, 128, 134 Acrylates, activated 1, 3 -, reactivity ratios 7 -, -, suspension copolymerization 13 Acrylic groups 49, 53 A-Acryloxy derivatives 37 Active ester method, graft copolymers 29 Alkyl esters, aminolysis 14 Aminolysis, alkyl esters 14 Amphigels, polymer-solvent compatibility 24... 

The grafting of nucleic acid base derivatives with a hydroxyl group onto poly(ethyleneimine) polymer backbone was also carried out by the activated ester method. Since the reactivity of the lactone is low, the direct reaction of the lactone derivative with poly(ethyleneimine) was not effective. Therefore, the lactone derivatives were at first hydrolyzed to the 3-hydroxybutyric acid derivatives, followed by condensation with poly(ethyleneimine) using the activated ester method. The grafting reaction was carried out in N,N-dimethylformamide, where a small amount of 4-pyrrolidinopyridine was added as an effective catalyst. Nucleic acid base contents of the polymers were determined by UV spectroscope of hydrolyzed samples. A quantitative calculations were made by using the corresponding carboxyethyl derivatives as standards. The nucleic acid base units (unit mol%) on the polymer are tabulated in Table 1. 

There are in general two ways to synthesize side chain polymers, polymerization of peptide-functional monomers or introduction of the peptide moiety afterwards, by grafting. The latter technique is based on the synthesis of polymers containing some form of functionality in the side chain, normally an activated ester moiety, which can further react with a peptide. The most commonly used method for the polymerization of monomers containing active esters is free radical polymerization. In particular many activated acrylate esters have been polymerized in this manner [12] (Table 1) for use in a wide variety of applications, from the preparation of polymer drug conjugates [13,14] to supports for solid phase peptide synthesis [15,16]. 

This review introduces the method of active ester mtheris, and discusses its application to the preparation of a variety erf specialty polymers, including amphiphilic gels, graft copolymers, and side chain reactive and liquid crystalline polymers. The polymerization and copolymerization of activated acrylates by solution and suspension techniques are discussed, and polymer properties such as comonomer distribution, molecular weights, C-NMR spectra and gel morphology are reviewed. Potential applications of these polymers are also highlighted, and the versatility of active ester synthesis as a new dimension of creativity in macromolecular chemistry is emphasized. 

Batch instruments are generally compatible with both Fmoc//Bu and Bck/ Bzl methods as well as polystyrene, polyethylene glycol-polystyrene graft (PEG-PS). and polyethylene oxide-polystyrene (PEO-PS) supports (for recent reviews see refs 31 and 32). For amino acid activation, protocols have been developed to include carbodiimide, aminium and phosphonium salts, and active esters (pcntafluorophenyl esters and acid halides). For batch instruments designed to monitor the Fmoc function, UV or conductivity detectors are used. 

Organometallic compounds and alkoxides add to activated double bonds and to functional groups such as ketones, esters, nitriles, and aldehydes. Many workers have taken advantage of this tendency and have attempted to prepare graft polymers by this method (2). A detailed description of these techniques and others like it is given in a recent review by Heller (3). 

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