The invention relates to the novel materials of formula (I), where: R is an optionally substituted L-aryl or L-heteroaryl, such that L is a single bond, alkyl, CO, or CO-alk, or L-X, with L being an alkyl and X being O or S; R is H or alkyl; R is an alkyl optionally substituted by Hal; and R is Hou Hal, wherein said materials are in any isomeric form and the salts thereof, to be used as drugs.