Convenient syntheses of 9-[4-hydroxy-3-(hydroxymethyl)butyl]guanine (penciclovir) and 9-[4-acetoxy-3-(acetoxymethyl)butyl]-2-amino-9h-purine (famciclovir)

Article abstract of DOI:10.1016/S0040-4020(99)00169-6

Guanine 11 was converted, in a one pot reaction, into 2-amino-6-[(4- chlorophenyl)sulfanyl]purine 9a in 88% isolated yield. 4-Acetoxy-3- (acetoxymethyl)butanol 123 was prepared from 2-chloroethanol in five steps and in 46% overall yield. The mesylate ester of compound 23 reacted with 9a in the presence of potassium carbonate with a high degree of regioselectivity (89%) to give the N-9 alkylated product 26 which was isolated in 80% yield. Acidic hydrolysis of the latter compound 26 gave penciclovir 4 in virtually quantitative yield. Penciclovir 4 and famciclovir 5 were prepared from 2- amino-6-[(4-chlorophenyl)sulfanyl]purine 9a in four and five steps, respectively, by procedures involving initial alkylation with 1,2- dibromoethane. The overall yields obtained were 65 and ca. 60%, respectively.