Patent ID: 8343937

Claim:
A method for the treatment of a flavivirus or pestivirus infection in a host, comprising contacting a cell infected with a flavivirus or a pestivirus with an anti-virally effective amount of a compound of Formula X, XI or XII: or a phosphate thereof, or a pharmaceutically acceptable salt or ester thereof, wherein: Base is a purine or pyrimidine base as defined herein; R 1 , R 2 and R 3 are independently H; phosphate; monophosphate; diphosphate; triphosphate; or a stabilized phosphate prodrug; acyl; alkyl; lower alkyl; sulfonate ester; alkyl sulfonyl; arylalkyl sulfonyl; methanesulfonyl; and benzyl, wherein the phenyl group is optionally substituted with one or more substituents as described in the definition of aryl given herein; a lipid; a phospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol; or other pharmaceutically acceptable leaving group which when administered in vivo is capable of providing a compound wherein R 1 , R 2 or R 3 is independently H or phosphate; R 6 is alkyl; or cyano; R 7 is OR 3 or hydroxy; and X is O, S, SO 2 or CH 2 .