Compounds of the general formula wherein R 1 is -(CHR') q -aryl or -(CHR') q -heteroaryl, which are unsubstituted or mono, di- or tri-substituted by lower alkyl, lower alkoxy, CF 3 or halogen, or is lower alkyl, lower alkenyl, -(CH 2) n -Si(CH 3) 3, -(CH 2) n -O-lower alkyl, -(CH 2) n -S-lower alkyl, -(CH 2) q -cycloalkyl, -(CH 2) n -[CH] m -(CF 2) p -CH q P( 3-q), or is -(CH 2) n -CR 2 -CF 3, wherein the two R radicals form together with the carbon atom a cycloalkyl ring; R' is hydrogen or lower alkyl; n is 1, 2 or 3; m is 0 or 1; p is 0, 1, 2, 3, 4, 5 or 6; q is 0, 1,2 or 3; R 2 is hydrogen or lower alkyl; R 3 is hydrogen, lower alkyl, -CH 2 CF 2 CF 3, CH 2 CF 3, (CH 2) 2 CF 3, CF 3, CHF 2, CH 2 F or is aryl, optionally mono, di or tri-substituted by halogen, or is -(CH 2) n NR 5 R 6, wherein R 5 and R 6 are independently from each other hydrogen or lower alkyl; R 4 is one of the following groups wherein R 7 is hydrogen, lower alkyl, -(CH 2) n -CF 3 or -(CH 2) n -cycloalkyl; R 8 is hydrogen, lower alkyl, -C -phenyl, -C -lower alkyl, -C O-(CH 2) n -cycloalkyl, -C O-(CH 2) n -lower alkyl, -C NH-(CH 2) n -lower alkyl or -C NH-(CH 2) n -cycloalkyl; R 9 is hydrogen, lower alkyl, -(CH 2) n -cycloalkyl or -(CH 2) n -CF 3; wherein the term "lower" in "lower alkyl" or "lower alkoxy" means that the group contains from 1 to 10 carbon atoms and the term "lower" in "lower alkenyl" means that the group contains from 2 to 10 carbon atoms; and to pharmaceutically suitable acid addition salts, optically pure enantiomers, racemates or diastereomeric mixtures thereof. R 1 is -(CHR') q -aryl or -(CHR') q -heteroaryl, which are unsubstituted or mono, di- or tri-substituted by lower alkyl, lower alkoxy, CF 3 or halogen, or is lower alkyl, lower alkenyl, -(CH 2) n -Si(CH 3) 3, -(CH 2) n -O-lower alkyl, -(CH 2) n -S-lower alkyl, -(CH 2) q -cycloalkyl, -(CH 2) n -[CH] m -(CF 2) p -CH q P( 3-q), or is -(CH 2) n -CR 2 -CF 3, wherein the two R radicals form together with the carbon atom a cycloalkyl ring; R' is hydrogen or lower alkyl; n is 1, 2 or 3; m is 0 or 1; p is 0, 1, 2, 3, 4, 5 or 6; q is 0, 1,2 or 3; R 2 is hydrogen or lower alkyl; R 3 is hydrogen, lower alkyl, -CH 2 CF 2 CF 3, CH 2 CF 3, (CH 2) 2 CF 3, CF 3, CHF 2, CH 2 F or is aryl, optionally mono, di or tri-substituted by halogen, or is -(CH 2) n NR 5 R 6, wherein R 5 and R 6 are independently from each other hydrogen or lower alkyl; R 4 is one of the following groups wherein R 7 is hydrogen, lower alkyl, -(CH 2) n -CF 3 or -(CH 2) n -cycloalkyl; R 8 is hydrogen, lower alkyl, -C -phenyl, -C -lower alkyl, -C O-(CH 2) n -cycloalkyl, -C O-(CH 2) n -lower alkyl, -C NH-(CH 2) n -lower alkyl or -C NH-(CH 2) n -cycloalkyl; R 9 is hydrogen, lower alkyl, -(CH 2) n -cycloalkyl or -(CH 2) n -CF 3; wherein the term "lower" in "lower alkyl" or "lower alkoxy" means that the group contains from 1 to 10 carbon atoms and the term "lower" in "lower alkenyl" means that the group contains from 2 to 10 carbon atoms; and to pharmaceutically suitable acid addition salts, optically pure enantiomers, racemates or diastereomeric mixtures thereof. R 7 is hydrogen, lower alkyl, -(CH 2) n -CF 3 or -(CH 2) n -cycloalkyl; R 8 is hydrogen, lower alkyl, -C -phenyl, -C -lower alkyl, -C O-(CH 2) n -cycloalkyl, -C O-(CH 2) n -lower alkyl, -C NH-(CH 2) n -lower alkyl or -C NH-(CH 2) n -cycloalkyl; R 9 is hydrogen, lower alkyl, -(CH 2) n -cycloalkyl or -(CH 2) n -CF 3;