Patent ID: 8193349

Claim:
A compound of formula (I) wherein: R1 is heteroaryl, wherein said heteroaryl is optionally substituted with one to three substituents selected from halogen, dialkylamino, alkoxy, heterocyclyl, wherein said heterocyclyl is further optionally substituted with one to three substituents selected from alkyl, hydroxy or alkanoyl, R2 is alkyl; R3 is HOC(O)—R9—O—C(O)—; R4 is alkyl or aryl-alkyl- optionally substituted by one to three alkyl or halogen; R5 is hydrogen; R6 and R7 are independently halogen, alkyl or alkoxy, wherein said alkyl is optionally substituted with one to three halogen; and R9 is (C1-C4) alkyl, (C3-C6) cycloalkyl, (C1-C4) alkyl-C3-6cycloalkyl or (C3-C6) cycloalkyl-alkyl; or a pharmaceutically acceptable salt thereof, or an optical isomer thereof; or a mixture of optical isomers thereof.