Metallo-organic systems with high

Metallo-organic Systems with High Thermal Stability... 

Institute for Industrial Research of Oslo, Norway. A unique metallo-organic catalyst system has been discovered which enables the selective trimerization of ethylene to 3-methyl-2-pentene. High temperature de-methanation of this compound results in the formation of isoprene in good yields. Similarly, since 1-butene and 2-butene are dimers of ethylene, they react with ethylene selectively in the liquid phase to produce 3-methyl-2-pentene. 

Another example of a protease-catalyzed commercial process, which in this case uses the enzyme in a synthetic mode, is the completely regio- and stereoselective production of the low-caloric sweetener aspartame developed by DSM-TOSOH [15] (Fig. 7.9). Aspartame is a dipeptide consisting of the amino acids phenylalanine and aspartic acid, which are coupled by the enzyme thermolysin from Bacillus thermoproteolyticus. For an efficient coupling, relatively high temperatures are required and the amount of water in the system must be kept low to drive the reaction in the desired direction. Thermolysin, which is a metallo-endoprotease, meets these two requirements. It is thermostable, and it works in an organic solvent, which is required to keep the water activity low. In practice, however, organic solvents were not necessary, since the product aspartame forms an insoluble complex with unreacted D-Phe-OMe, which crystallizes out of the aqueous medium. 

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