Patent ID: 8809549

Claim:
A compound of formula I or a pharmaceutically acceptable salt thereof, wherein R 1 is C1-C3 alkyl, R 2 and R 3 independently from each other represent C1-C3 alkanediyl, Y 1 and Y 2 represent oxygen, and R 4 and R 5 form a 5- to 7-membered ring structure together with the nitrogen located between R 4 and R5, wherein the ring structure is selected from the group consisting of pyrrolidine, piperidine, piperazine and morpholino wherein the atoms of the ring structure formed by R 4 and R 5 together with the nitrogen located between R 4 and R 5 are unsubstituted, or substituted with a substituent selected from the group consisting of C1-C4 alkyl, C1-C4 alkoxy, C1-C4 alkylsulfide, unsubstituted amino (—NH 2 ) and dialkylamino in which alkyl is C1-C4 alkyl.