Patent ID: 7659429

Claim:
A compound of the formula X wherein: R1 is hydrogen, or alkyl having 1, 2, 3 or 4 carbon atoms; R6 is alkyl having 1, 2, 3, 4, 5 or 6 carbon atoms; or R6 is —(CH 2 ) t -phenyl or —O-phenyl, which are unsubstituted or substituted by 1, 2 or 3 radicals selected from the group consisting of —O u —(CH 2 ) v —CF 3 , alkoxy having 1, 2, 3 or 4 carbon atoms, alkyl having 1, 2, 3 or 4 carbon atoms, —SO 2 CH 3 ; t is zero, 1, 2, 3 or 4; u is zero or 1; v is zero, 1, 2 or 3; or R6 is —(CH 2 ) w -heteroaryl which is unsubstituted or substituted by 1, 2 or 3 radicals selected from the group consisting of —O x —(CH 2 ) y —CF 3 , alkoxy having 1, 2, 3 or 4 carbon atoms and alkyl having 1, 2, 3 or 4 carbon atoms, —SO 2 CH 3 ; w is zero, 1, 2, 3 or 4; x is zero or 1; y is zero, 1, 2 or 3; and R3 and R4, independently of one another, are hydrogen or F; and the salts thereof.