Patent ID: 7534918

Claim:
A compound represented by the following structural formula: wherein R 1 and R 2 are independently of each other unsubstituted or substituted and selected from C 1 -C 10 alkyl, C 2 -C 10 alkenyl, cycloalkyl, aryl, heterocyclyl, heteroaryl, C 1 -C 10 alkyl-C 2 -C 10 alkenyl, C 1 -C 10 alkylcycloalkyl, C 1 -C 10 alkylaryl, C 1 -C 10 alkylheterocyclyl and C 1 -C 10 alkylheteroaryl; R 3 is hydrogen or C 1 -C 10 alkyl; R 4 is hydrogen or C 1 -C 10 alkyl; and n is 5 or 6; or a stereoisomer, enantiomer, racemate, or a pharmaceutically acceptable salt thereof.