A compound of the formula [I - b]: or compound of formula enantiómeUn [I - b]: or enantiómeUn compound of the formula [I - b]: or its enantiomer ß-L or a pharmaceutically acceptable salt Mro ß-L or a pharmaceutically acceptable salt Mro ß-L or a pharmaceutically acceptable salt thereof, wherein: D is hydrogen W1 is CH W2 is Nismo, wherein: D is hydrogen W1 is CH W2 is Nismo, wherein: D is hydrogen W1 is CH W2 is N each X1 and X2 is independently hydrogen, hal each X1 and X2 is independently hydrogen, hal each X1 and X2 is independently hydrogen, halogen (F, Cl, Br or I), NH2, NHR4 or NR4R4 R2 is hógeno (F, Cl, Br or I), NH2, NHR4 or NR4R4 R2 is hógeno (F, Cl, Br or I), NH2, NHR4 or NR4R4 R2 is hydrogen, halogen (F, Cl, Br or I) or OH R2 is hiidrógeno, halogen (F, Cl, Br or I) or OH R2 is hiidrógeno, halogen (F, Cl, Br or I) or OH R2 is hydrogen, Cl, Br, I or OH, R3 is hydrogen, halógenodrógeno, Cl, Br, I or OH, R3 is hydrogen, halógenodrógeno, Cl, Br, I or OH, R3 is hydrogen, halogen (F, Cl , Br or I) or OH R3 is hydrogen, Cl, Br or (F, Cl, Br or I) or OH R3 is hydrogen, Cl, Br or (F, Cl, Br or I) or OH R3 is hydrogen, Cl, Br or I each R4 and R4 is independently hydrogen, I each R4 and R4 is independently hydrogen, I each R4 and R4 is independently hydrogen, lower alkyl, lower alkenyl, aryl, or lower arylalkyl, lower alkenyl, aryl, or lower arylalkyl, lower alkenyl, aryl, or arylalkyl of formaque for nucleoside fórmullalquilo of formaque for nucleoside fórmullalquilo of formaque for the nucleoside of the general formula (I - b) at least one of R2 and R2 is generally hydra (I - b) at least one of R2 and R2 is generally hydra (I - b) at least one of R2 and R2 is hydrogen and at least one of R3 and R3 is hydrogen in dógeno and at least one of R3 and R3 is hydrogen in dógeno and at least one of R3 and R3 is hydrogen wherein "lower alkyl" refers to a group alquonde "lower alkyl" refers to a group alquonde "lower alkyl" refers to a saturated linear alkyl, branched or c
