The present invention relates to compounds of formula 1 or pharmaceutically acceptable salt thereof, wherein R1, R2, R3, R5, R4, R5, R6 and X− have the meanings as indicated in the specification, to their use as a medicament, to their use in the treatment of a disease selected from among respiratory diseases or complaints and allergic diseases of the airways, to pharmaceutical composition comprising at least one of said compound or a pharmaceutically acceptable salt thereof, as well as to medicament combinations containing one or more of said compounds or a pharmaceutically acceptable salt thereof.