A compound of the formula I ** Formula ** in which: R1 is CO2-tert-Bu, CO2Et, phenyl-C1-3alkyl, heteroaryl-C1-3alkyl, phenyl or heteroaryl, wherein said heteroaryl group is selected from the group consisting of pyridinyl, pyridine N-oxide, pyrimidinyl, thiophenyl, pyrrolyl, thiazolinyl, imidazolinyl or quinolyl and said phenyl or said heteroaryl is optionally substituted one to three times by moieties independently selected from the group consisting of: (a ) C1-6 alkyl, (b) C1-6 alkoxy, (c) C1-6 haloalkyl, (d) C1-6 haloalkoxy, (e) carboxyl, (f) CONR7aR7b, (g) (C1-6 alkoxy) - carbonyl, (h) cyano, (i) SO2-C1-6 alkyl, (j) SO2NR8aR8b, (k) halogen, (l) nitro, (m) cyano-C1-3 alkyl； (n) NR10aR10b, (o) NR10aSO2-C1-6 alkyl, (p) CHR11aR11bCOR12, (q) hydroxyl and (r) C1-6 heteroalkyl which is an alkyl radical as defined herein, wherein one, two or three atoms of hydrogen have been substituted by a substituent independently selected from the group consisting of ORa, -NRbRc, and S (O) nRd (where n is an integer from 0 to 2), it being understood that the point of attachment of the heteroalkyl radical is a through a carbon atom, where Ra is hydrogen, acyl, alkyl, cycloalkyl, or cycloalkylalkyl； Rb and Rc are independently from each other hydrogen, acyl, alkyl, cycloalkyl, or cycloalkylalkyl； and when n is 0, R1 is hydrogen, alkyl, cycloalkyl or cycloalkylalkyl, and when n is 1 or 2, Rd is alkyl, cycloalkyl, cycloalkylalkyl, amino, acylamino or alkylamino； R2 is -CN, -CH>； = CHCN, C1-3 alkyl or halogen； R3 is hydrogen, halogen, amino or C1-6 haloalkyl； R4 is hydrogen or amino； R5a and R5b are independently hydrogen, C1-6 alkyl, C1-6 alkoxy or halogen； R6a and R6b independently are hydrogen or, together, are ethylene； R7a and R7b (i) taken independently, one of R7a and R7b is hydrogen, C1-6 alkyl or C3-7 cycloalkyl and the other of R7a and R7b is selected from the group consisting of hydrogen, C1-6 alkyl, C1 heteroalkyl -6, which is an alkyl radical as defined herein, wherein one,
