Derivatives useful as antiviral agents

A compound of general formula (Ia):

• Wherein X is O, S, NOH, N—NH2, or NRx wherein Rx is H or C1-C6Alkyl, R2, R3 are H, CH3, F, Cl, Br, I, NR′R″, OH, C(═O)OH, C6-C10 aryl, or a 5 to 7 membered heterocycle;
• R1b is H or NO2;
• n is 1 or 2;
• is a double bond;
• R1a is a ring system A:
• R4, R5, R6, R7 and R8 are each independently selected from H, Cl, Br, I, F, OH, C1-C6 alkyl, C2-C8 alkenyl, C1-C6 fluoroalkyl, C1-C6 fluoroalkoxy, NO2, and C1-C6 alkoxy, or two of R4, R5, R6, R7, R8 together form with the carbon atoms to which they are attached a 1,3-dioxolane or a 1,4-dioxane;
• when R2 and R3 are CH3, then R1b cannot be NO2;
• and with the exclusion of the compounds of formula (Ia) wherein:
• X is O;
• R1b is H or NO2;
• R2═R3 are H or CH3;
• R1a is m- or p-NO2Ph;
• n is 1;
• and the stereoisomeric forms, mixtures of stereoisomeric forms or pharmaceutically acceptable salts forms thereof.