Patent ID: 7524854

Claim:
A compound of formula I wherein R 1 represents the groups whereby in these groups R 5 is hydrogen, lower alkyl with 1 to 4 carbon atoms, or the group wherein R 8 represents lower alkyloxy, lower alkylamino, or lower alkyl with 1 to 4 carbon atoms; R 9 represents lower alkyl with 1 to 4 carbon atoms; R 8 and R 9 together form a 5- or 6-membered heterocyclic ring containing one to two hetero atoms which can be the same or different and are oxygen or nitrogen; R 6 represents hydrogen, halogen, nitro, or lower alkyloxy; R 7 represents hydrogen; R 2 and R 3 independently represent hydrogen, lower alkyl with 1 to 3 carbon atoms, or together a lower alkylene group with 1 to 3 carbon atoms bridging the oxygen atoms and forming a five, six or seven membered ring; R 4 represents hydrogen; or a pharmaceutically acceptable salt thereof.