In order to gain information on structure activity relationships of peptidic inhibitors of Zn-dependent metalloproteinases "hemorrhagins", the conformationally restricted model N-(2-furoyl)-(Z)-alpha,beta-didehydroleucyl-L-tryptophan 2 was synthesized and its activity compared to that of related previously studied substrates. The new model 2 exhibits an inhibitory activity on proteinase II from Crotalus Adamanteus snake venom, sensibly lower than that of related substrates. This result indicates that the reduction of the conformational space due to the presence of the alpha,beta-didehydro-amino acid residue in 2 does not favour the fitting and binding at the enzyme active site.