Patent ID: 7666856

Claim:
A compound of formula I wherein: R 1 , R 2 and R 3 are independently selected from the group consisting of hydrogen, COR 4 , C(═O)OR 4 and C(═O)CHR 5 NHR 6 ; or R 1 and R 3 are H and R 2 is the monophosphate, diphosphate or triphosphate ester; R 4 is independently selected from the group consisting of (a) C 1-18 unbranched or branched alkyl, (b) C 1-18 haloalkyl, (c) C 3-8 cycloalkyl, (d) C 1-10 heteroalkyl and (e) phenyl said phenyl optionally substituted with one to three groups independently selected from C 1-3 alkyl, C 1-3 alkoxy, halogen, cyano or nitro; R 5 is hydrogen, C 1-10 alkyl, phenyl or C 1-3 phenylalkyl said phenyl optionally substituted with one to three groups independently selected from the group consisting of halogen, hydroxy, C 1-3 alkoxy, C 1-3 alkyl, cyano and nitro; R 6 is hydrogen or C 1-6 alkoxy; or, acid addition salts thereof.