Compound of the formula (I) in which X represents an oxygen atom or an =N-OH group and R represents a group selected from (II) or one of its esters and/or its addition salts with pharmaceutically acceptable acids, particularly as a cytoprotective, preferably cardioprotective and/or neuroprotective, medicament; the compounds of formula I in which R is R2, R3, R4, R5 or R6, as new compounds; and also their preparation process, and the use.