A compound of formula I ** Formula ** in which R1 represents phenyl that is unsubstituted or mono, di or tri-substituted, in which the substituents are independently selected from the group consisting of halogen, (C1-C4) alkyl and fluoroalkyl (C1-C3)； Z represents hydrogen, (C1-C4) alkyl, cyclopropyl, cyclopropylmethyl, hydroxy (C1-C3) alkyl, carboxyalkyl (C1-C3), cyano-C1-C3 alkyl, P (O) (R6) 2-alkyl (C1-C3), 1H-tetrazol-5-yl-C1-C3 alkyl or benzyl； R2 represents cyano, -COO-, -CONH2, -COOR3, hydroxy (C1-C3) alkyl, (C1-C2) alkoxy (C1-C2) alkyl, carboxy10 (C1-C3) alkyl, 1H-tetrazol-5 -yl or -N-R5； with the proviso that, if R2 represents -COOR3, Z represents carboxy-(C1-C3) alkyl or P (O) (R6) 2-(C1-C3) alkyl； Ra represents hydrogen or methyl； R3 represents (C1-C4) alkyl； R4 represents (C1-C6) alkoxy or benzyloxy； R5 represents hydrogen or tert-butoxycarbonyl； R6 represents hydroxy, (C1-C4) alkoxy, R7-OCH2O- or R8-(C1-C4) -NH- alkyl； R7 represents (C1-C4) alkylcarbonyl or (C1-C4) alkoxycarbonyl； and R8 represents (C1-C4) alkoxycarbonyl； or a salt of said compound.Un compuesto de fórmula I**Fórmula** en la que R1 representa fenilo que está no sustituido o mono, di o tri-sustituido, en el que los sustituyentes se seleccionan independientemente del grupo que consiste en halógeno, alquilo (C1-C4) y fluoroalquilo (C1-C3)； Z representa hidrógeno, alquilo (C1-C4), ciclopropilo, ciclopropilmetilo, hidroxi-alquilo (C1-C3), carboxialquilo (C1-C3), ciano-alquilo (C1-C3), P(O)(R6)2-alquilo (C1-C3), 1H-tetrazol-5-il-alquilo (C1-C3) o bencilo； R2 representa ciano, -COO-, -CONH2, -COOR3, hidroxi-alquilo (C1-C3), alcoxi (C1-C2)-alquilo (C1-C2), carboxi10 alquilo (C1-C3), 1H-tetrazol-5-ilo o -N-R5； con la condición que, si R2 representa -COOR3, Z representa carboxi-alquilo (C1-C3) o P(O)(R6)2-alquilo (C1-C3)； Ra representa hidrógeno o metilo； R3 representa alquilo (C1-C4)； R4 representa alcoxi (C1-C6) o benciloxi； R5 representa hidrógeno o terc-butoxicarbonilo； R6 representa hidroxi,
