Patent ID: 8268838

Claim:
A compound of formula (I) any of its stereoisomers or any mixture of its stereoisomers, or a pharmaceutically acceptable salt thereof, wherein R 1 represents hydrogen or alkyl; one of R 2 , R 3 and R 4 represents alkyl, hydroxy-alkyl, alkoxy-alkyl, halo, trifluoromethyl, trifluoromethoxy, hydroxy or alkoxy; and the other two of R 2 , R 3 and R 4 , independently of each other, represent hydrogen, alkyl, hydroxy-alkyl, alkoxy-alkyl, halo, trifluoromethyl, trifluoromethoxy, hydroxy or alkoxy; R 5 represents phenyl optionally substituted with one or more substituents selected from the group consisting of alkyl, halo, trifluoromethyl, trifluoromethoxy, alkoxy and cyano; and R 6 represents R′OC(═O)—, wherein R′ represents alkyl, alkoxy, alkoxy-allyl or adamantanyl.