Compounds of formula (I):wherein: R1represents a hydrogen atom or a group of formula COR4, or R1represents a group of formula (A):R2represents a group of formula NR5R6, or R2represents a nitrogen-containing heterocyclic group, an aryl group or a heteroaryl group, R3represents a hydrogen atom or an alkyl group, m represents an integer between 1 and 6 inclusive, n represents 0, 1 or 2, their optical isomers, and also addition salts thereof with a pharmaceutically acceptable acid. Medicaments.本發明係關於式(I)化合物:其中:R1代表氫原子或式COR4之基團,或R1代表式(A)之基團:R2代表式NR5R6之基團,或R2代表含氮雜環基團、芳基或雜芳基,R3代表氫原子或烷基,m代表介於包括1與6間之整數,n代表0、1或2,其光學異構體,以及其與醫藥上可接受酸之加成鹽。藥劑。