Enzyme inhibition

Claim 1

Polypeptide analogues of the formula: ##STR27## where X=H or an N-protective group: F, Cl, Br, I, --CF 3 , --OH, --OR or --R (R=C 1 -C 6 alkyl) or R--O--CO-- where R═t-butyl, benzyl, 2,2,2-trichloroethyl or R 6 --SO 2 -- where R 6 =Ph, α-naphthyl β-naphthyl or one or more amino acyl residues as such or in N-protected form bearing a group X above; Y=absent, or glycine, or D- or L-phenylalanine or a lipophilic amino acid residue selected from the group consisting of Phg, Cha, α-Nal, β-Nal and p-iodophenylalanyl; Z=L- or D-proline or a ring homologue selected from the group consisting of azetidine-2-carboxylic acid and piperidine-2-carboxylic acid, or L- or D-valine, or N-methyl-alanine, or glycine; or Y and Z are as: ##STR28## where the peptide bond --CO--NH-- between Y and Z has been reduced (and protected) to give --CH 2 --N(X)--, X being a protective group as defined above; A= ##STR29## where: (i) ##STR30## (ii) R 2 =H, lower alkyl (C 1 -C 4 ) or 1-hydroxy-ethyl, (iii) R 3 =a protective group as defined above; (iv) configuration at the asymmetric centres* is either R or S Arg or both Pro and Arg may be absent, Pro or Pro substituted with hydroxy-proline and Arg or Arg substituted with Z, Tos or --NO 2 B=D- or L-valine or D- or L-proline or --NH--(CH 2 ) n --CO--, where n=0-5, or absent W=(i) --OR 4 , where R 4 is hydrogen or an O-protecting group; or (ii) --NHR 5 or --N(R 5 ) 2 where each R 5 is hydrogen or an N-protecting group; or (iii) a group with one or more further amino acyl residues or B-W represents an aminoalcohol derivative of B as such or in protected form, and where further in said compounds of Formula I the two terminals are optionally linked by a peptide bond to form a cyclic structure.