A compound of formula (I): wherein: ▪ A represents a linear or branched (C 1 -C 6 ) alkyl chain; ▪ R 1 represents: • a hydrogen atom, • a halogen atom, • an acyl group CO-R 7 or a sulfonyl group SO 2 -R 7 , wherein R 7 represents a (C 1 -C 6 ) alkyl group, • a sulfonamide group SO 2 -NR 8 R 9 wherein R 8 and R 9 independently represent a hydrogen atom, or a (C 1 -C 6 ) alkyl group, or • a (C 1 -C 6 ) alkyl, (C 1 -C 6 ) alkoxy, (C 1 -C 6 ) alkylmercapto, thio-(C 1 -C 6 )alkyl or (C 1 -C 6 ) alkylsulfonyl group, said groups being optionally substituted by at least one halogen atom; ▪ R 1 ' represents a hydrogen atom or a hydroxyl group, preferably a hydrogen atom; ▪ R 2 , R 3 , R 4 and R 5 are identical or different and each represents a hydrogen atom or a (C 1 -C 6 ) alkyl group ; and ▪ R 6 represents: • a hydrogen atom, • a (C 1 -C 6 ) alkyl group, optionally substituted by at least one hydroxyl group at the end of the alkyl chain, • a (C 1 -C 4 ) alkylacyloxy group, • a (C 1 -C 4 ) alkyl-ORio group, wherein R 10 represents: - a (C 1 -C 4 ) alkyl group, optionally substituted by at least one hydroxyl group at the end of the chain, - or a COR 11 group, R 11 being a (C 1 -C 6 ) alkyl group optionally substituted by an amino group at end of the alkyl chain; or one of its pharmaceutically acceptable salts, for a use for treating spasticity. ▪ A represents a linear or branched (C 1 -C 6 ) alkyl chain; ▪ R 1 represents: • a hydrogen atom, • a halogen atom, • an acyl group CO-R 7 or a sulfonyl group SO 2 -R 7 , wherein R 7 represents a (C 1 -C 6 ) alkyl group, • a sulfonamide group SO 2 -NR 8 R 9 wherein R 8 and R 9 independently represent a hydrogen atom, or a (C 1 -C 6 ) alkyl group, or • a (C 1 -C 6 ) alkyl, (C 1 -C 6 ) alkoxy, (C 1 -C 6 ) alkylmercapto, thio-(C 1 -C 6 )alkyl or (C 1 -C 6 ) alkylsulfonyl group, said groups being optionally substituted by at least one halogen atom; • a hydrogen atom, • a halogen atom, • an acyl group CO-R 7 or a sulfonyl group SO 2 -R 7 , wherein R 7 represents a (C 1 -C 6 ) alkyl group, • a sulfonamide group SO 2 -NR 8 R 9 wherein R 8 and R 9 independently represent a hydrogen atom, or a (C 1 -C 6 ) alkyl group, or • a (C 1 -C 6 ) alkyl, (C 1 -C 6 ) alkoxy, (C 1 -C 6 ) alkylmercapto, thio-(C 1 -C 6 )alkyl or (C 1 -C 6 ) alkylsulfonyl group, said groups being optionally substituted by at least one halogen atom; ▪ R 1 ' represents a hydrogen atom or a hydroxyl group, preferably a hydrogen atom; ▪ R 2 , R 3 , R 4 and R 5 are identical or different and each represents a hydrogen atom or a (C 1 -C 6 ) alkyl group ; and ▪ R 6 represents: • a hydrogen atom, • a (C 1 -C 6 ) alkyl group, optionally substituted by at least one hydroxyl group at the end of the alkyl chain, • a (C 1 -C 4 ) alkylacyloxy group, • a (C 1 -C 4 ) alkyl-ORio group, wherein R 10 represents: - a (C 1 -C 4 ) alkyl group, optionally substituted by at least one hydroxyl group at the end of the chain, - or a COR 11 group, R 11 being a (C 1 -C 6 ) alkyl group optionally substituted by an amino group at end of the alkyl chain; • a hydrogen atom, • a (C 1 -C 6 ) alkyl group, optionally substituted by at least one hydroxyl group at the end of the alkyl chain, • a (C 1 -C 4 ) alkylacyloxy group, • a (C 1 -C 4 ) alkyl-ORio group, wherein R 10 represents: - a (C 1 -C 4 ) alkyl group, optionally substituted by at least one hydroxyl group at the end of the chain, - or a COR 11 group, R 11 being a (C 1 -C 6 ) alkyl group optionally substituted by an amino group at end of the alkyl chain; - a (C 1 -C 4 ) alkyl group, optionally substituted by at least one hydroxyl group at the end of the chain, - or a COR 11 group, R 11 being a (C 1 -C 6 ) alkyl group optionally substituted by an amino group at end of the alkyl chain; <EOS>