Bifunctional reagents advantage

Crystals constitute the most concentrated form of enzyme and they can therefore be attractive as catalysts. In the crystallisation of a crude enzyme preparation a considerable purification of the enzyme can be achieved which is a further advantage. In order to stabilise the enzyme crystals to make them useful catalysts they are often crosslinked with bifunctional reagents such as glutaraldehyde. Very high catalytic activity and stability has been reported for these crosslinked enzyme crystals, some of which are commercially available (Margolin, 1996). 

It is also worthwhile to outline at this place the immobilization procedure that was used for the preparation of type I CSPs A bifunctional linker with a terminal isocyanate on one side and a triethoxysilyl group on the other end (3-isocyanatopropyl triethoxysilane) was reacted with the native cinchona alkaloids quinine and quinidine and subsequently the resultant carbamate derivative in a second step with silica [30], Remaining silanols have been capped with silane reagents, yet, are less detrimental for acidic solutes because of the repulsive nature of such electrostatic interactions. CSPs prepared in such a way lack the hydrophobic basic layer of the thiol-silica-based CSPs mentioned earlier, which may be advantageous for the separation of certain analytes. 

Another relatively simple system for the epoxidation of tri- and c/r-disubstituted olefins is formamide-hydrogen peroxide in an aqueous medium. This reagent has the advantage of being pH-independent, which makes it attractive for biochemically mediated transformations. No reaction was observed in the case of /ran.v-disubstituted and terminal olefins. With bifunctional alkenes, the more reactive double bond is selectively epoxidized [95TL4015]. 

In the following case a carbonate could not be removed in the presence of the diolide using hydrolytic conditions. It was found that treatment with the bifunctional Grignard reagent cleaved the carbonate in 65% yield by taking advantage of the intramolecularity of the second addition. ... 

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