Abstract: Compound of formula (I): wherein: R1 represents hydrogen or wherein A is as defined in the description, R2 and R3 each independently represents alkyl, cycloalkyl, heterocycloalkyl, optionally substituted aryl, optionally substituted heteroaryl, cycloalkylalkyl, heterocycloalkylalkyl, optionally substituted arylalkyl, optionally substituted heteroarylalkyl,or optionally substituted aminoalkyl or R2 and R3, together with the carbon atom carrying them, form cycloalkyl or monocyclic heterocyclic group, substituted or unsubstituted, R40 represents hydrogen or a group selected from optionally substituted alkyl, optionally substituted alkenyl and optionally substituted alkynyl or Q or —V—Q wherein V represents alkylene, alkenylene or alkynylene and Q represents optionally substituted cycloalkyl, optionally substituted aryl, optionally substituted heterocycloalkyl,or optionally substituted heteroaryl, R41 and R5 together form a bond or each represents hydrogen, R6,