Anti-viral nucleosides

A compound of formula I

• wherein:
• R1, R2, R3 and R4 are independently selected from the group consisting of hydrogen, COR5, C(═O)OR5, C(═O)SR5, C(═O)NHR5 and COCH(R6)NHR7;
• R5 is independently selected from the group consisting of C1-8 unbranched or branched alkyl, C1-18 unbranched or branched alkenyl, C1-18 unbranched or branched alkynyl, C1-18 lower haloalkyl, C3-8 cycloalkyl, C3-8 cycloalkyl-C1-3 alkyl, phenyl optionally substituted with one to three substituents independently selected from the group consisting of halo, C1-6 alkyl, C1-6 lower alkoxy, C1-6 lower thioalkyl, C1-6 lower alkyl sulfinyl, C1-6 lower alkyl sulfonyl, nitro and cyano, CH2Ph wherein in phenyl ring is optionally substituted as described above, and CH2OPh wherein in phenyl ring is optionally substituted as described above;
• R6 is independently selected from the group consisting of the side chains of naturally occurring amino acids and C1-5 unbranched or branched alkyl;
• R7 is selected from the group consisting of hydrogen and R5OCO;
• or,
• R6 and R7 taken together are (CH2)3;
• and,
• hydrates, solvates, clathrates and acid addition salts thereof.