Abstract: The present invention comprises fibrinogen receptor antagonist compounds, compositions containing them and methods for using them to inhibit fibrinogen binding to blood platelets. Compounds of the invention have the following formula ##STR1## wherein Z is ##STR2## X is COOH, CH.sub.2 SH or SH; R.sup.1 is Y--R.sup.3, wherein R.sup.3 is alkyl and Y is amino, pyridinyl, pyrimidinyl or piperidinyl;R.sup.2 is H, alkyl, aryl, or arylalkyl; andR.sup.4 is alkyl, heteroalkyl, aryl or heteroaryl, wherein the aryl or heteroaryl group can be mono- or bi-cyclic.