Bicyclic nucleosides and nucleotides as therapeutic agents

A compound of the formula (I) which may be a D-or L-nucleoside or nucleotide, or a salt thereof;

• wherein:
• each R is independently selected from the group consisting of H, CF3, optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, optionally substituted aryl, optionally substituted acyl, optionally substituted cycloalkyl, optionally substituted cycloalkenyl, optionally substituted heteroaryl, optionally substituted heterocyclyl, and optionally substituted arylalkyl;
• or C-5 monophosphate, diphosphate and triphosphate derivatives thereof, or C-5 mono, di or triphosphate mimics;
• B is a group of formula (II)
• wherein, if Z is a participant in a π bond (double bond), Z is independently selected from N or C-G;
• or, if Z is not a participant in a π bond (double bond), Z is independently selected from O, S, Se, NR, NOR, NNR2, CO, CS, CNR, SO, S(O)2, SeO, Se(O)2 or C(G)2, wherein each G is independently selected from the group consisting of H, halogen, OR, SR, NR2, NROR, N3, COOR, CN, CONR2, C(S)NR2, C(═NR)NR2, and R;
• and
• where any two adjacent Z are not both selected from O, S, and Se, or not both selected from CO, CS, CNR, SO, S(O)2, SeO, and Se(O)2;
• wherein, if X is a participant in a π bond (double bond), X is C;
• or if X is not a participant in a π bond (double bond), X is CR or N;
• wherein, if R″ is a participant in a π bond (double bond), R″ is O, S, Se, NR, NOR, and NNR2;
• or if R″ is not a participant in a π bond (double bond), R″ is OR, SR, F, Cl, R, or SeR;
• and
• dashed lines (- - -) indicate a possible π or double bond.