Exploiting Enzyme Chemoselectivity and Regioselectivity

Chemoselectivity and regioselectivity are enzymatic properties of significant synthetic interest [1]. Their common feature is the fact that the enzymatic preference toward one of the several functional groups present on a substrate molecule is dictated by its accessibility to the protein active site (steric effect) and not necessarily by its chemical reactivity. 

These findings, together with other previously collected information on the regioselectivity of hydrolases toward alcohols, monosaccharides, and polyhydrox-ylated steroids dissolved in organic solvents [3-6], have since been extended and exploited by several research groups as a protective step in a synthetic sequence [7] or as an efficient way to obtain specific compounds with potential applications 

Organic Synthesis with Enzymes in Non-Aqueous Media. Edited by Giacomo Carrea and Sergio Riva Copyright 2008 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 978-3-527-31846-9 

Chemoselectivity is the preferential reaction of a chemical reagent with one functional group in the presence of other similar functional groups [1]. 

The above-described acylation of the sugar moiety of the nucleotide adenosine (3) [2] has been followed by a series of papers reporting on the chemoselec-tive enzymatic modification of natural compounds carrying both hydroxyl and amino groups. In addition to the extensive work on nucleosides developed by Gotor and coworkers [8], the biocatalyzed esterification of the hydroxylated alkaloids castanospermine (4) and 1-deoxynojirimidn (5) should be mentioned. Both compounds were selectively acylated at their C-6 and/or C-2 OH by the protease subtilisin, despite the presence of a potentially more reactive amino functions [9]. 

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