Crystal and Molecular Structures of the Antiviral Acyclonucleoside 9-[4-Hydroxy-3-(hydroxymethyl)butyl]guanine (BRL 39123, Penciclovir) and its Prodrug 9-[4-Acetoxy-3-(acetoxymethyl)butyl]-2-aminopurine (BRL 42810, Famciclovir)

Abstract

The crystal and molecular structures of two closely related antiviral purine derivatives are reported. In 9-[4-hydroxy-3-(hydroxymethyl)butyl]guanine (2) the plane of the acyclic N9 substituent is orthogonal to the purine ring. In crystals of 2 there is an extensive network of intermolecular hydrogen bonds. In 9-[4-acetoxy-3-(acetoxymethyl)butyl]-2-aminopurine (3) characteristic changes in the geometry of the pyrimidine ring in comparison with 2 are observed. In crystals of the 2-aminopurine derivative 3 there is an absence of major hydrogen bonding interactions and there are π-π interactions between parallel overlapping pyrimidine moieties.