A compound of formula I wherein n represents 0, 1, 2 or 3; R 1a represents H or (C 1 -C 3)alkyl; R 2a and R 2b independently from each other represent H or (C 1 -C 3)alkyl; R 3a and R 3b independently from each other represent H or (C 1 -C 3)alkyl; R 4 represents H, (C 1 -C 3)alkyl, or (C 2 -C 3)alkyl-NR 4a R 4b, wherein R 4a and R 4b are independently from each other H or (C 1 -C 3)alkyl; R 5 represents H, (C 1 -C 3)alkyl, or (C 2 -C 3)alkyl-NR 5a R 5b, wherein R 5a and R 5b are independently from each other H or (C 1 -C 3)alkyl; or R 2a and R 2b together with the carbon atom which bears them form a 3 to 6-membered cycloalkyl ring; or R 4 and R 5 together with the nitrogen atom which bears them form a 4 to 6-membered heterocycloalkyl ring; or R 4 and R 5 together with the nitrogen atom which bears them form a 6 to 8-membered bicyclic heterocycloalkyl ring, which bicyclic heterocycloalkyl ring may optionally be substituted by a group NR 6 R 7, wherein R 6 and R 7 are independently from each other H or (C 1 -C 3)alkyl; or R 4 and R 5 together with the nitrogen atom which bears them and the adjacent CR 2a R 2b or CR 3a R 3b together form an amidine group; or R 1a and R 3a, together with the carbon atoms which bear them and the carbon atom which connects these latter two atoms, form a 4 to 6-membered cycloalkyl ring, whereby R 2a, R 2b and R 3b each represent H, and n represents 1; or R 1a and R 4, together with the carbon and nitrogen atoms which bear them and the carbon atom(s) which connect(s) the latter two atoms, form a 4 to 6-membered heterocycloalkyl ring, whereby R 2a, R 2b, optional R 3a and optional R 3b each represent H, n represents 0 or 1, and said 4 to 6-membered heterocycloalkyl ring optionally contains a substituent selected from OCH 3 and CH 3; or R 2a and R 4 together with the carbon and nitrogen atoms which bear them and the optional carbon atom(s) which connect the latter two atoms, form a 4 to 6-membered heterocycloalkyl ring, whereby R 1a, optional R 3a and optional R 3b each represent H, R 2b represents H, NH 2 or OH, and n represents 0, 1 or 2; U 1 represents N or CH, U 2 represents N, CH, C-O(C 1 -C 3)alkyl, or C-CN, U 3 represents N or CH and U 4 represents N or CH, it being understood that at most three of U 1, U 2, U 3 and U 4 can represent N at the same time; V 1 represents N or CH, V 2 represents N or CH, V 3 represents N or CH and V 4 represents N or CH, it being understood that at most three of V 1, V 2, V 3 and V 4 can represent N at the same time; X represents CH or N; Q represents O or S; or a salt of this compound. n represents 0, 1, 2 or 3; R 1a represents H or (C 1 -C 3)alkyl; R 2a and R 2b independently from each other represent H or (C 1 -C 3)alkyl; R 3a and R 3b independently from each other represent H or (C 1 -C 3)alkyl; R 4 represents H, (C 1 -C 3)alkyl, or (C 2 -C 3)alkyl-NR 4a R 4b, wherein R 4a and R 4b are independently from each other H or (C 1 -C 3)alkyl; R 5 represents H, (C 1 -C 3)alkyl, or (C 2 -C 3)alkyl-NR 5a R 5b, wherein R 5a and R 5b are independently from each other H or (C 1 -C 3)alkyl; or R 2a and R 2b together with the carbon atom which bears them form a 3 to 6-membered cycloalkyl ring; or R 4 and R 5 together with the nitrogen atom which bears them form a 4 to 6-membered heterocycloalkyl ring; or R 4 and R 5 together with the nitrogen atom which bears them form a 6 to 8-membered bicyclic heterocycloalkyl ring, which bicyclic heterocycloalkyl ring may optionally be substituted by a group NR 6 R 7, wherein R 6 and R 7 are independently from each other H or (C 1 -C 3)alkyl; or R 4 and R 5 together with the nitrogen atom which bears them and the adjacent CR 2a R 2b or CR 3a R 3b together form an amidine group; or R 1a and R 3a, together with the carbon atoms which bear them and the carbon atom which connects these latter two atoms, form a 4 to 6-membered cycloalkyl ring, whereby R 2a, R 2b and R 3b each represent H, and n represents 1; or R 1a and R 4, together with the carbon and nitrogen atoms which bear them and the carbon atom(s) which connect(s) the latter two atoms, form a 4 to 6-membered heterocycloalkyl ring, whereby R 2a, R 2b, optional R 3a and optional R 3b each represent H, n represents 0 or 1, and said 4 to 6-membered heterocycloalkyl ring optionally contains a substituent selected from OCH 3 and CH 3; or R 2a and R 4 together with the carbon and nitrogen atoms which bear them and the optional carbon atom(s) which connect the latter two atoms, form a 4 to 6-membered heterocycloalkyl ring, whereby R 1a, optional R 3a and optional R 3b each represent H, R 2b represents H, NH 2 or OH, and n represents 0, 1 or 2; U 1 represents N or CH, U 2 represents N, CH, C-O(C 1 -C 3)alkyl, or C-CN, U 3 represents N or CH and U 4 represents N or CH, it being understood that at most three of U 1, U 2, U 3 and U 4 can represent N at the same time; V 1 represents N or CH, V 2 represents N or CH, V 3 represents N or CH and V 4 represents N or CH, it being understood that at most three of V 1, V 2, V 3 and V 4 can represent N at the same time; X represents CH or N; Q represents O or S; or a salt of this compound.