Patent ID: 8039501

Claim:
A compound represented by the structural formula (I): wherein: R 1 is —C(═O)—R 4 or —S(═O) 2 —R 4 , R 2 is —C(═O)—R 6 , R 3 is hydrogen, —C(═O)—R 7 , —C(═O)—OR 7 or aryl-C 1-7 alkyl; R 4 is selected from the group consisting of R 5 , —OR 5 , —NHR 5 and —SR 5 , R 5 is selected from the group consisting of hydrogen, C 1-10 alkyl, C 3-10 cycloalkyl, C 2-10 alkenyl, C 2-10 alkynyl, aryl, aryl-C 1-7 alkyl, and saturated, partly unsaturated or aromatic heterocyclic groups, wherein each of said alkyl groups may be substituted with one or more substituents independently selected from the group consisting of amino, hydroxyl, sulfhydryl and methoxy, R 6 is selected from the group consisting of C 2-10 alkyl, C 3-10 cycloalkyl, C 2-10 alkenyl, C 2-10 alkynyl, aryl, arylalkyl, and saturated, partly unsaturated or aromatic heterocyclic groups, wherein each of said alkyl groups may be substituted with one or more substituents independently selected from the group consisting of amino, hydroxyl, sulfhydryl and methoxy, R 7 is selected from the group consisting of C 1-10 alkyl, C 2-10 alkenyl, aryl and aryl-C 1-10 alkyl, wherein each of said alkyl groups may be substituted with one or more substituents independently selected from the group consisting of amino, hydroxyl, sulfhydryl and methoxy, and wherein each of said C 2-10 alkenyl or aryl groups may be substituted with one or more substituents independently selected from the group consisting of halogen, alkyl, alkoxy, nitro, cyano and hydroxy, a stereoisomer thereof, or a salt thereof.