PHARMACEUTICALS

摘要

Preparation of the anti-viral agents penciclovir or famciclovir comprises: (a) forming a purine by closing an imidazole or pyrimidine ring; (b) reacting the purine with a precursor with a suitable side-chain in position 9; (c) converting the side-chain into (i) 4-hydroxy-3-hydroxymethylbutyl or (ii) 4-acetoxy-3-acetoxymethylbutyl; (d) converting the purine into guanine (using (i) or 2-aminopurine (using (ii)). The purine is of formula (I). R1 = halo, OH or a sulphonate; R2 = a side-chain in position 9; X1 = H, OH or precursor. Converting R1 into an amino gives the anti-viral agents.