Biocatalytic separation of N-7/N-9 guanine nucleosides

Vorbroggen coupling of trimethylsilylated 2-N-isobutanoylguanine with peracetylated pentofuranose derivatives to generally yield inseparable N-7/N-9 glycosyl mixtures is described. The two isomers could be separated biocatalytically by Novozyme-435-mediated selective deacetylation of the 5'-O-acetyl group of peracetylated N-9 guanine nucleosides.