Bicyclic compounds and their use as ligands in integrin receptors.

A compound of formula ** ** wherein R1 represents optionally substituted aryl or optionally substituted heteroaryl; R2 represents hydrogen, halogen, C1-4 alkyl or C1-4 alkoxy; R3 is an alkylene chain, a chain alkenylene or alkynylene chain; R5 represents hydrogen or C1-4 alkyl; R13 is selected from acyl, acylamino, alkoxy, alkoxycarbonyl, alkylenedioxy, alkylsulfinyl, alkylsulfonyl, alkylthio, aroyl, aroylamino, aryl, arylalkyloxy, arylalkyloxycarbonyl, arylalkylthio, aryloxy, aryloxycarbonyl, arylsulfinyl, arylsulfonyl, arylthio, carboxy, cyano, halo, heteroaroyl, heteroaryl, heteroarylalkyloxy, heteroaroylamino, heteroaryloxy, hydrogen, hydroxy, nitro, trifluoromethyl, Y1Y2N-, Y1Y2NCO-, Y1Y2NSO2-, Y1Y2N-C2-6 alkylene-Z1-, alkyl- C (= O) -Y1N-, alkyl-SO2- Y1N- or C1-15 alkyl optionally substituted with aryl, heteroaryl, hydroxy, or Y1Y2N-; L2 represents an alkylene or alkenylene linkage where each is optionally substituted with R6 (wherein R6 represents C1-15 alkyl, alkenyl, alkynyl, aryl, arylalkyl, arylalkenyl, arylalkynyl, cycloalkyl, cycloalkylalkyl, cycloalkylalkenyl, cycloalkylalkynyl, cycloalkenyl, cycloalkenylalkyl, heteroaryl, heteroarylalkyl, heteroarylalkenyl, heteroarylalkynyl, heterocycloalkyl or heterocycloalkylalkyl).