ABSTRACT
References .......................................................................................................................... 523
502 Biocatalysis in the Pharmaceutical and Biotechnology Industries
Many synthetic compounds structurally related to natural nucleosides are characterized by
biopharmacological effects that include anticancer [1,2] or antiviral [3,4] activities. Several
compounds are effective against viruses that are causative agents of severe infections, such as
the human immunodeficiency virus (HIV) [5,6]. Synthetic antiviral compounds that are struc-
turally related to nucleosides may be characterized by modifications in the carbohydrate or base
moiety, while substitution of the furanose ring with an analogous cyclopentane system generates
carbocyclic nucleosides. In these compounds, the problem associated with the presence of the
b-N-glycosidicbond,makingnucleoside structure vulnerable tochemicalor enzymatic hydrolysis and favoring loss of pharmacological activity in a nucleosidic drug, is eliminated. Only a few
carbocyclonucleosides are naturally occurring, such as aristeromycin and neplanocin that have
been isolated from microbial fermentation [7,8]. In general, carbocyclonucleosides are prepared
by chemical total synthesis that sometimes uses chemoenzymatic methodologies [9-11]. Many
synthetic acyclic analogs of nucleosides (acyclonucleosides) also present important antiviral
activity and for the synthesis of two leading products such as acyclovir and ganciclovir chemical
and chemoenzymatic procedures have already been reviewed [12].
