The invention provides a method of rearranging a compound of formula (I) wherein R and R' are selected independently from hydrogen and C1-12alkyl; and R1 and R2 are selected independently from hydrogen hydroxy halo C1-12alkyl- or aryl carbonate amino mono- or di-C1-12alkylamino C1-12alkyl- or arylamido C1-12alkyl- or arylcarbonyl C1-12alkyl- or arylcarboxy C1-12alkyl- or arylcarbamoyl C1-12alkyl C2-12alkenyl C2-12alkynyl aryl heteroaryl C1-12alkoxy aryloxy azido C1-12alkyl- or arylthio C1-12alky...

UNA FORMULACION FARMACEUTICA TOPICA ACUOSA O LIPOSOLUBLE PARA EL TRATAMIENTO DE INFECCIONES VIRICAS DE LA PIEL O DE LAS MUCOSAS COMPRENDE AL MENOS UN 30 % DE GLICOL PROPILENO AL MENOS 0\'\'75 % DE PENCICLOVIR Y DE 0\'\'5 % A 1 % DE CETOMACROGOL 1000.

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 positi...