article 14 purine nucleoside 12 nonhuman 10 Escherichia coli 6 Nucleoside phosphorylases 6 Purine Nucleosides 6 catalysis 6 drug synthesis 6 Aspergillus 4 Catalysis 4 Glycosylation 4 Nucleosides 4 antiviral activity 4 biocatalyst 4 deprotection reaction 4 drug structure 4 enzyme synthesis 4 glycosylation 4 hydrolysis 4 nucleoside 4 nucleoside derivative 4 pyrimidine nucleoside 4 unclassified drug 4 2 amino 6 chloropurine riboside 2 2-amino-6-chloropurine riboside 2 6 chloropurine ribonucleoside 2 6-chloropurine riboside 2 Acylase I 2 Adenosine deaminase 2 Amidohydrolases 2