A compound of formula wherein R 1 is selected from the group R 1a consisting of heteroaryl, wherein the heteroaryl group is optionally substituted with 1 to 3 substituents independently selected from the group consisting of C 1- s-alkyl-, C 1-5 -alkyl-O-, C 1-5 -alkyl-C -, C 1-5 -alkyl-O-C -, H C-, HOOC-, C 3-6 -cycloalkyl-, (R 3) 2 N-, (R 3) 2 N-C 1-5 -alkyl-, (R 3) 3 N + -C 1-5 -alkyl-, (R 3) 2 N-C -, NC-, HO-, oxo, C 1-5 -alkyl-S -, C 1-5 -alkyl-S 2 -, halogen and imidazolyl, and wherein the above mentioned C 1-5 -alkyl-, C 1-5 -alkyl-O-, C 1-5 -alkyl-C -, C 1-5 -alkyl-O-C -, C 3-6 -cycloalkyl-, (R 3) 2 N-, (R 3) 2 N-C 1-5 -alkyl-, (R 3) 3 N + -C 1-5 -alkyl-, (R 3) 2 N-C -, C 1-5 -alkyl-S -, C 1-5 -alkyl-S 2 - and imidazolyl groups are optionally substituted with 1 to 5 substituents independently selected from the group consisting of oxo, halogen, NC-, and HO-, and wherein the heteroaryl group is a mono- or bicyclic-ring system containing one to three heteroatoms selected from N, O or S r, wherein r=0, 1 or 2, consisting of 5 to 10 ring atoms wherein at least one of the heteroatoms is part of an aromatic ring; R 2 is selected from the group R 2a consisting of H-, halogen and C 1-3 -alkyl-, wherein the above mentioned C 1-3 -alkyl-groups may optionally be substituted with 1 to 7 substituents independently from each other selected from the group consisting of halogen NC-, and HO-; R 3 is selected from the group R 3a consisting of H- and C 1-3 -alkyl-, wherein the above mentioned C 1-3 -alkyl-groups may optionally be substituted with 1 to 7 substituents independently from each other selected from the group consisting of halogen NC-, and HO-; or a salt thereof. R 1 is selected from the group R 1a consisting of heteroaryl, wherein the heteroaryl group is optionally substituted with 1 to 3 substituents independently selected from the group consisting of C 1- s-alkyl-, C 1-5 -alkyl-O-, C 1-5 -alkyl-C -, C 1-5 -alkyl-O-C -, H C-, HOOC-, C 3-6 -cycloalkyl-, (R 3) 2 N-, (R 3) 2 N-C 1-5 -alkyl-, (R 3) 3 N + -C 1-5 -alkyl-, (R 3) 2 N-C -, NC-, HO-, oxo, C 1-5 -alkyl-S -, C 1-5 -alkyl-S 2 -, halogen and imidazolyl, and wherein the above mentioned C 1-5 -alkyl-, C 1-5 -alkyl-O-, C 1-5 -alkyl-C -, C 1-5 -alkyl-O-C -, C 3-6 -cycloalkyl-, (R 3) 2 N-, (R 3) 2 N-C 1-5 -alkyl-, (R 3) 3 N + -C 1-5 -alkyl-, (R 3) 2 N-C -, C 1-5 -alkyl-S -, C 1-5 -alkyl-S 2 - and imidazolyl groups are optionally substituted with 1 to 5 substituents independently selected from the group consisting of oxo, halogen, NC-, and HO-, and wherein the heteroaryl group is a mono- or bicyclic-ring system containing one to three heteroatoms selected from N, O or S r, wherein r=0, 1 or 2, consisting of 5 to 10 ring atoms wherein at least one of the heteroatoms is part of an aromatic ring; heteroaryl, wherein the heteroaryl group is optionally substituted with 1 to 3 substituents independently selected from the group consisting of C 1- s-alkyl-, C 1-5 -alkyl-O-, C 1-5 -alkyl-C -, C 1-5 -alkyl-O-C -, H C-, HOOC-, C 3-6 -cycloalkyl-, (R 3) 2 N-, (R 3) 2 N-C 1-5 -alkyl-, (R 3) 3 N + -C 1-5 -alkyl-, (R 3) 2 N-C -, NC-, HO-, oxo, C 1-5 -alkyl-S -, C 1-5 -alkyl-S 2 -, halogen and imidazolyl, and wherein the above mentioned C 1-5 -alkyl-, C 1-5 -alkyl-O-, C 1-5 -alkyl-C -, C 1-5 -alkyl-O-C -, C 3-6 -cycloalkyl-, (R 3) 2 N-, (R 3) 2 N-C 1-5 -alkyl-, (R 3) 3 N + -C 1-5 -alkyl-, (R 3) 2 N-C -, C 1-5 -alkyl-S -, C 1-5 -alkyl-S 2 - and imidazolyl groups are optionally substituted with 1 to 5 substituents independently selected from the group consisting of oxo, halogen, NC-, and HO-, and wherein the heteroaryl group is a mono- or bicyclic-ring system containing one to three heteroatoms selected from N, O or S r, wherein r=0, 1 or 2, consisting of 5 to 10 ring atoms wherein at least one of the heteroatoms is part of an aromatic ring; R 2 is selected from the group R 2a consisting of H-, halogen and C 1-3 -alkyl-, wherein the above mentioned C 1-3 -alkyl-groups may optionally be substituted with 1 to 7 substituents independently from each other selected from the group consisting of halogen NC-, and HO-; R 3 is selected from the group R 3a consisting of H- and C 1-3 -alkyl-, wherein the above mentioned C 1-3 -alkyl-groups may optionally be substituted with 1 to 7 substituents independently from each other selected from the group consisting of halogen NC-, and HO-;