Enzymic Synthesis of Glycosides

Obviously, the presence of a high concentration of alcohol facilitates the synthesis and high concentration of water the hydrolysis. In the Fischer method for the synthesis of the glycosides (Chapter IV), the catalyst is an acid, but, as shown by the excellent work of Bourquelot, H4rissey, and Bridel, enzymes also may be employed with some advantages over the use of acids. When acids are used, all the various isomers are formed, and the equilibrium is very complex although certain constituents predominate under the equilibrium conditions. The enzymes are very much more selective in their catalysis. Almond emulsin catalyzes the sjmthesis and hydroly- 

For the synthesis of jS-glucosides, the reactive form of glucose is jS-glucose the concentration of this form determines the reaction rate and the position of the equilibrium 75). The equilibrium constants for the synthesis of several glucosides are as follows  

The in vivo synthesis of glycosides, as discussed earlier in this chapter (and Chapter IX), probably occurs by transglycosidation, because of the smaller changes in free energy. The glycosidases presumably are purely hydrolytic in their natural function or act as transglycosidases.  

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