Enzymatic polymerizations

The first report of an enzymatic ROP of 2,5-morpholinediones appeared in 1999, when Hocker, Feng and colleagues showed that alternating polydepsipeptides could be prepared from 2,5-morpholinediones with different alkyl substituents (methyl, isopropyl, seobutyl) at the 3- or 6-position, and using different enzymes. 

The field of enzymatic polymerization has been reviewed in detail (59,60). Enzymes have been industrially established in large-scale synthesis and degradation, such as the use of  

Enz5matic polymerization is an important issue for green polymer chemistry to save energy in production processes and to reduce the formation of undesired by-products since the reaction is mostly selective. In general, an enz5mie catalyzed reaction proceeds much faster than a conventional reaction, by lowering the activation energy. 

T ical Pol5mers that can be synthesized by an in vitro enzymatic catalysis are summarized in Table 1.8. The basic concept of the in 

Oxidoreductases Transferases Polyphenols, polyanilines, vinyl polymers Polysaccharides, cyclic oligosaccharides, polyesters Polysaccharides, polyesters, polycarbonates, polyamides, polyphosphates, polythioesters 

The recent developments in Upase catalyzed synthesis of polyesters have been reviewed (61). A series of diacids, such as succinic add, glutaric acid, adipic acid, and sebacic acid and diols, such as 1,4-but-anediol, 1,6-hexanediol, and 1,8-octanediol have been pol5merized in solution and in bulk using lipase as a catalyst (62,63). 

Both starch and cellulose are prepared in nature by enzymatic, chain growth polymerization reactions of glucose nucleotide monomers [6]. In both cases, the monomer precursor is glucose-1-phosphate, which is enzymatically converted to the nucleotide derivative. The latter, in turn, complexes with an enzyme to form the activated monomer at the active site on the enzyme, which also contains the growing polymer molecule, as schematically illustrated below for the enzymatic polymerization of cellulose  

Lipases catalyze the polymerization of lactones [Duda et al., 2002 Gross et al., 2001 Kobayashi, 1999 Kobayashi et al., 2001]. The reaction mechanism is similar to that for the enzymatic polymerization of hydroxyacids (Sec. 2-17a-2). Lipase reacts with lactone to produce enzyme-activated hydroxyacid and some of the latter reacts with water to produce hydroxyacid (Eqs. 7-81). Hydroxyacid and enzyme-activated hydroxyacid react to initiate polymerization (Eq. 7-82). Propagation proceeds by nucleophilic attack of 

Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Japan 

Enzymes are proteins catalyzing all in vivo biological reactions. Enzymatic catalysis can also be utilized for in vitro reactions of not only natural substrates but some unnatural ones. Typical characteristics of enzyme catalysis are high catalytic activity, large rate acceleration of reactions under mild reaction conditions, high selectivities of substrates and reaction modes, and no formation of byproducts, in comparison with those of chemical catalysts. In the field of organic synthetic chemistry, enzymes have been powerful catalysts for stereo- and regioselective reactions to produce useful intermediates and end-products such as medicines and liquid crystals.  

In the recent decades, an enzyme-catalyzed polymerization ( enzymatic polymerization ) has been of increasing importance as a new trend in macro-molecular science. Enzyme catalysis has provided new synthetic strategy for useful polymers, most of which are difficult to produce by conventional chemical 

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More recently, Heise and coworkers have shown that DKR can be combined with enzymatic polymerization for the synthesis of chiral polyesters from racemic secondary diols in one pot [34] (Figure 4.12). 

Enzymes are generally classified into six groups. Table 1 shows typical polymers produced with catalysis by respective enzymes. The target macromolecules for the enzymatic polymerization have been polysaccharides, poly(amino acid)s, polyesters, polycarbonates, phenolic polymers, poly(aniline)s, vinyl polymers, etc. In the standpoint of potential industrial applications, this chapter deals with recent topics on enzymatic synthesis of polyesters and phenolic polymers by using enzymes as catalyst. 

Five-membered unsubstituted lactone, y-butyrolactone (y-BL), is not polymerized by conventional chemical catalysts. However, oligomer formation from y-BL was observed by using PPL or Pseudomonas sp. lipase as catalyst. Enzymatic polymerization of six-membered lactones, 8-VL and l,4-dioxan-2-one, was reported. 8-VL was polymerized by various lipases of different origins. The molecular weight of the enzymatically obtained polymer was relatively low (less than 2000). 

Enzymatic synthesis of aliphatic polyesters was also achieved by the ringopening polymerization of cyclic diesters. Lactide was not enzymatically polymerized under mild reaction conditions however, poly(lacfic acid) with the molecular weight higher than 1 x 10" was formed using lipase BC as catalyst at higher temperatures (80-130°C). Protease (proteinase K) also induced the polymerization however, the catalytic activity was relatively low. 

Aromatic polyesters were efficiently synthesized from aromatic diacid divinyl esters. Lipase CA induced the polymerization of divinyl esters of isoph-thalic acid, terephthalic acid, and p-phenylene diacetic acid with glycols to give polyesters containing aromatic moiety in the main chain. The highest molecular weight (7.2 x 10 ) was attained from a combination of divinyl isophthalate and 1,10-decanediol. Enzymatic polymerization of divinyl esters and aromatic diols also afforded the aromatic polyesters. ... 

The enzymatic polymerization of 12-hydroxydodecanoic acid in the presence of 11-methacryloylaminoundecanoic acid conveniently produced the methacrylamide-type polyester macromonomer. Lipases CA and CC were active for the macromonomer synthesis. Enzymatic selective monosubstitution of a hydroxy-functional dendrimer was demonstrated. Lipase CA-catalyzed polymerization of 8-CL in the presence of the first generation dendrimer gave the poly(8-CL)-monosubstituted dendrimer. 

As described above, the enzymatic polymerization of phenols was often carried out in a mixture of a water-miscible organic solvent and a buffer. By adding 2,6-di-0-methyl-(3-cyclodextrin (DM-(3-CD), the enzymatic polymerization of water-insoluble m-substituted phenols proceeded in buffer. The water-soluble complex of the monomer and DM-(3-CD was formed and was polymerized by HRP to give a soluble polymer. In the case of phenol, the polymerization took place in the presence of 2,6-di-O-methyl-a-cyclodextrin (DM-a-CD) in a buffer. Only a catalytic amount of DM-a-CD was necessary to induce the polymerization efficiently. Coniferyl alcohol was oxidatively polymerized in the presence of a-CD in an aqueous solution. ... 

R A. Monnard et al. from the laboratory of D. W. Deamer also worked on ice/eutectic phases at 255 K. They studied the influence of solutions of inorganic ions (such as Na+, CD, Mg2+, Ca2+ and Fe2+) both on the formation of vesicles and on non-enzymatic polymerization of activated RNA monomers (Monnard et al., 2002). 

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