Patent ID: 7553866

Claim:
A compound of formula I or a pharmaceutically acceptable salt, an optical isomer or a mixture of optical isomers of the compound, wherein: X is C 1 -C 4 alkylene or Ar; Ar is phenylene which is unsubstituted or substituted with one or more substituent(s) independently selected from carboxy, halo, nitro, C 1 -C 4 alkyl, C 1 -C 4 alkoxy, phenyl, phenoxy and benzyloxy; L is a bond, —CR 1 R 2 —, —O—, —S—, or —NH; Y is —CR 3 R 4 —; Z is —(CR 5 R 6 ) 2 —; and R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are independently hydrogen, C 1 -C 4 alkyl or C 2 -C 4 alkenyl, wherein the alkyl or alkenyl is unsubstituted or substituted with one or more substituent(s); provided that when L is a bond then X is methylene, propylene, butylene, or Ar.