The present article comprehensively reviews the macromolecular synthesis using enzymes as catalysts. Among the six main classes of enzymes, the three classes, oxidoreductases, transferases, and hydrolases, have been employed as catalysts for the in vitro macromolecular synthesis and modification reactions. Appropriate design of reaction including monomer and enzyme catalyst produces macromolecules with precisely controlled structure, similarly as in vivo enzymatic reactions. The reaction controls the product structure with respect to substrate selectivity, chemo-selectivity, regio-selectivity, stereoselectivity, and choro-selectivity. Oxidoreductases catalyze various oxidation polymerizations of aromatic compounds as well as vinyl polymerizations. Transferases are effective catalysts for producing polysaccharide having a variety of structure and polyesters. Hydrolases catalyzing the bond-cleaving of macromolecules in vivo, catalyze the reverse reaction for bond forming in vitro to give various polysaccharides and functionalized polyesters. The enzymatic polymerizations allowed the first in vitro synthesis of natural polysaccharides having complicated structures like cellulose, amylose, xylan, chitin, hyaluronan, and chondroitin. These polymerizations are "green" with several respects; nontoxicity of enzyme, high catalyst efficiency, selective reactions under mild conditions using green solvents and renewable starting materials, and producing minimal byproducts. Thus, the enzymatic polymerization is desirable for the environment and contributes to "green polymer chemistry" for maintaining sustainable society.
New double stimuli-responsive poly(α-N-substituted γ-glutamine) has been developed, which was synthesized by the reaction of poly(γ-glutamic acid) with amino alcohols. Appropriate combinations of the amino alcohols provided the biodegradable poly(amino acid) exhibiting a sharp lower critical solution temperature (LCST) in water. Furthermore, the phase transition temperature was highly sensitive to pH changes.
A chitin−chitosan hybrid polysaccharide (2) having a β(1→4)-linked alternating structure of an N-acetyl-d-glucosamine (GlcNAc) unit and a d-glucosamine (GlcN) unit was synthesized via chitinase-catalyzed polymerization of an oxazoline derivative of a GlcNβ(1→4)GlcNAc monomer (1). Monomer 1 was designed as a transition-state analogue substrate (TSAS) monomer for chitinase catalysis, which belongs to the glycoside hydrolase family 18. Monomer 1 was effectively polymerized by the catalysis of enzymes from Bacillus sp., Serratia marcescens and Streptomyces griseus, under weak alkaline conditions, giving rise to a water-soluble hybrid polysaccharide (2) in good yields. Molecular weights of 2 reached 2020 with using chitinase from Serratia marcescens, which corresponds to 10−12 saccharide units.
Abstract Introduction Historical Outline Ring‐opening Polymerization of Cyclic Monomers Polymerization of Lactones Polymerization of Other Cyclic Monomers Copolymerization of Cyclic Monomers Single‐step Synthesis of End‐functionalized Polyesters Polymerization of Dicarboxylic Acid Derivatives and Glycols Polyester Synthesis from Dicarboxylic Acids Polyester Synthesis from Dicarboxylic Acid Esters Polyester Synthesis from Acid Anhydride Derivatives Polycarbonate Synthesis by Enzymatic Polycondensation Polycondensation of Hydroxyacid Derivatives Lipase‐catalyzed Modification of Polymers Relevant Patents Outlook and Perspectives
Peroxidase-catalyzed oxidative polymerization of fluorine-containing phenols has been performed in a mixture of a water-miscible organic solvent and buffer at room temperature under air. The monomers used were 2,6-difluorophenol, 3- and 4-fluorophenols. In the polymerization of 2,6-diflurophenol catalyzed by horseradish peroxidase (HRP), effects of an organic solvent, buffer pH, and their mixed ratio have been systematically investigated with respect to the polymer yield and molecular weight. The resulting polymer was soluble in common polar organic solvents and showed good water repellent property. From NMR and IR data, it was supposed that the polymer was of mainly 2,6-difluoro-1,4-oxyphenylene unit. Elemental analysis showed that the elimination of a small amount of the fluorine atom took place during the polymerization. HRP catalysis induced the polymerization of 3- and 4-fluorophenols, yielding a new class of fluorine-containing polyphenols.
Abstract Racemic compounds containing a phosphorus or a sulfur atom as a chiral center were resolved by high-performance liquid chromatography on optically active (+)-poly(triphenylmethyl methacrylate). The resolved compounds include insecticides such as O-ethyl O-(4-nitrophenyl) phenylphosphonothionate (EPN), O-(4-cyanophenyl)-O-ethyl phenylphosphonothionate (cyanofenfos), and 2-methoxy-4H-1,3,2-benzo-dioxaphosphorin 2-sulfide (salithion).
Abstract Enzymatic ring-opening polymerization of a 13-membered lactone, 12-dodecanolide (DDL), was performed in the presence of acyclic esters in bulk by using lipase catalyst. The acyl group was introduced at the terminal by adding a fatty acid vinyl ester. Effects of the chain length and concentration of the vinyl ester on the introduced ratio (functionality) and molecular weight of the polymer have been examined. The quantitative acylation of the terminal was achieved by using lipases derived from Pseudomonas family under appropriate reaction conditions. Methacryl- and ω-alkenyl-type polyester macromonomers were synthesized by the polymerization of DDL in the presence of vinyl methacrylate and vinyl 10-undecenoate, respectively. This process could be extended to single-step synthesis of polyester telechelics. The polymerization in the presence of divinyl sebacate produced a telechelic polymer having a carboxylic acid group at each end. In using a fatty acid ethyl ester or an acetic acid alkyl ester as additive, on the other hand, the quantitative introduction of the corresponding acyl group was not achieved.
