Role of Temperature in Suppression of the Formation of Pummerer's Type Ketone in Enzymatic Polymerization of 4-Propylphenol: An in-Situ Variable Temperature 1H NMR Study

Enzymes as Green Catalysts for Precision Macromolecular Synthesis

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.

Synthesis of Novel Halogen-Free Phenol Based Polymers and their utilization as Flame Retardant in Polypropylene system

Increasing awareness of toxicity of halogenated flame retardants (FRs) has resulted in stringent regulations that require the elimination of their use in plastics. Consequently, there is considerable interest for the development of new varieties of high performance FRs. Here, we report the synthesis of new class of polyphenol based FR additives. Preliminary investigations indicate that these FR materials can possibly work through a combination of radical scavenging and char-formation. The thermal stability and char yield of polyphenol samples were investigated by thermogravimetric analysis (TGA). Thermal characterization indicated that these polymers produce significant amount of carbonaceous char upon combustion.

A strategy for the synthesis of the fargenone/fargenin family of natural products: synthesis of the tricyclic core

A synthesis of the core ring structure of the fargenin/fargenone family of natural products is presented. The general strategy is based upon biosynthetic speculation and exploits a cascade reaction, which transforms a spirocyclic dienone into the core ring system via a deprotonation-oxy-Michael-Wittig olefination sequence. This study represents the first synthesis work towards this family of natural products.