Substrate specificity of fucosyl transferase III: An efficient synthesis of sialyl Lewis(x)-, sialyl Lewis(a)-derivatives and mimetics thereof

Fucosyl transferase III (FucT III) has previously been characterized as the most general enzyme of the FucT family, as judged from its ability to cata lyze the transfer of fucose to both Gal beta(1-3)GlcNAc and Gal beta(1-4)Gl cNAc. In order to explore the synthetic potential of FucT III for the enzym atic synthesis of sialyl Lewis(x) and sialyl Lewis(a) derivatives, its subs trate specificity has been probed using a number of natural substrate mimet ics. A remarkable range of acceptor substrates was found when N-acetyl gluc osamine was replaced by D-glucal, (R,R)-1,2-cyclohexanediol and (R,R)-butan -2,3-diol. Although the reaction rates were low compared to the reaction wi th the natural substrates, they proved to be sufficient for the synthesis o f preparative amounts.