Compounds of formula wherein - A is selected from the following rings: with each of R6, which may be in position 5, 6, 7, or 8 of the phenyl ring of the naphthoquinone or in position 2, 3, or 4 of the quinoline-5,8-dione, representing independently a hydrogen atom, a halogen atom, a hydroxy group, a linear or branched (C 1 -C 4)alkyl group, a di- or tri-fluoromethyl group, a trifluoromethoxy group, a pentafluorosulfanyl group, n being an integer comprised between 0 and 4 and R7 representing a methyl group, - X represents -C - or -CHY- with Y selected from the group consisting of hydrogen atom, hydroxy group, and (C 3 -C 6)cycloalkyl group, - R1, R2, R3, R4, R5 represent each independently of the others:. a hydrogen atom,. a halogen atom selected from the group consisting of Br, Cl and F,. a hydroxy group,. a linear or branched (C 1 -C 4)alkyl group selected from the group consisting of methyl and t -butyl,. a di- or trifluoromethyl group,. a methoxy group,. a trifluoromethoxy group,. a pentafluorosulfanyl group. - NO 2,. - CN,. -COOR14 with R14 representing hydrogen atom or methyl group,. -CONH(CH 2) 2 CN. -NHBoc,. a group selected from the group consisting of. a phenyl group substituted in para by a t -butyl group, -NO 2, -N(CH 3) 2, or -NHC(CH 3) 3, with the proviso that the compounds of formula are not selected from the group consisting of - A is selected from the following rings: with each of R6, which may be in position 5, 6, 7, or 8 of the phenyl ring of the naphthoquinone or in position 2, 3, or 4 of the quinoline-5,8-dione, representing independently a hydrogen atom, a halogen atom, a hydroxy group, a linear or branched (C 1 -C 4)alkyl group, a di- or tri-fluoromethyl group, a trifluoromethoxy group, a pentafluorosulfanyl group, n being an integer comprised between 0 and 4 and R7 representing a methyl group, - X represents -C - or -CHY- with Y selected from the group consisting of hydrogen atom, hydroxy group, and (C 3 -C 6)cycloalkyl group, - R1, R2, R3, R4, R5 represent each independently of the others:. a hydrogen atom,. a halogen atom selected from the group consisting of Br, Cl and F,. a hydroxy group,. a linear or branched (C 1 -C 4)alkyl group selected from the group consisting of methyl and t -butyl,. a di- or trifluoromethyl group,. a methoxy group,. a trifluoromethoxy group,. a pentafluorosulfanyl group. - NO 2,. - CN,. -COOR14 with R14 representing hydrogen atom or methyl group,. -CONH(CH 2) 2 CN. -NHBoc,. a group selected from the group consisting of. a phenyl group substituted in para by a t -butyl group, -NO 2, -N(CH 3) 2, or -NHC(CH 3) 3, with the proviso that the compounds of formula are not selected from the group consisting of. a hydrogen atom,. a halogen atom selected from the group consisting of Br, Cl and F,. a hydroxy group,. a linear or branched (C 1 -C 4)alkyl group selected from the group consisting of methyl and t -butyl,. a di- or trifluoromethyl group,. a methoxy group,. a trifluoromethoxy group,. a pentafluorosulfanyl group. - NO 2,. - CN,. -COOR14 with R14 representing hydrogen atom or methyl group,. -CONH(CH 2) 2 CN. -NHBoc,. a group selected from the group consisting of. a phenyl group substituted in para by a t -butyl group, -NO 2, -N(CH 3) 2, or -NHC(CH 3) 3,