Aminoacid derivs. which are tachykinin antagonists

Aminoacid derivs. of formula (I) and their diastereomers and salts are new. In (I), A = 1,2-cyclopentylene or -(HC(asterisk)R6); asterisk indicates L or D configuration; R6 = H, opt. branched 1-4C alkyl (opt. substd.) or Ph; R1 = H or 1-3C alkyl (opt. substd.); R2 = H, Ph (opt. substd.), pyridyl, 1-5C alkyl (opt. substd.) by linear 1-4C alkyl (opt. substd.), phenyl(2-3C)alkyl (opt. substd.) or NR1R2 ; R3 = H, 1-4C alkyl (opt. substd.) linear 1-4C alkyl (substd. in position 2, 3 or 4), aminocarbonyl(1-2C)alkyl (opt. substd.), where, unless otherwise stated, in R3, all the alkyl and alkaroyl gps. contain 1-3 C atoms and the alkoxy contain 1-4 C atoms; R4 = H or 1-3C alkyl (opt. substd.); R5 = e.g. amino protecting gp., 1-8C alkyl (opt. substd. in position 1, 2, 3 or 4), 2-10C alkanoyl (opt. mono-substd.), phenylcarbonyl or Me (substd. by e.g. diphenylmethane, phenyloxyphenyl etc.); X = 2H, O or S; In R1-R6, Ph gps. is opt. mono or di-substd. by F, Cl, Br, Me, OH or MeO; the amino protecting gps. are e.g. phenyl(1-3C)alkoxycarbonyl (opt. mono substd. on the Ph ring with halogen, NO2 or Ph or opt. disubstd. on the Ph ring with MeO), 2-5C alkoxycarbonyl or fluoren-9-yl methoxycarbonyl.