A compound of formula: Y-O-W Wherein: W is H or -C(=O)-X; X is X a, X b, X c, X d or X e,: R 1a to R 10a, R 1b to R 10b, R 5c to R 10c, R 5d to R 10d, R 5e to R 10e and R 21a, R 21b, R 21c, R 21d and R 11e are each independently selected from H and C 1 -C 6 alkyl; R 11a to R 20a, R 11b to R 20b, R 11c to R 20c, R 11d to R 20d are each independently selected from H, halogen, notably fluorine, hydroxy, and C 1 -C 6 alkoxy; Ar is a phenylene group or a 5 membered heteroarylene group, said phenylene and heterorylene groups being optionally substituted with one to four groups selected from C 1 -C 6 alkyl; n is 0 or 1; m is 0, 1 or 2; o is 0, 1 or 2; provided that m+n+o =3; p is 0 or 1; q is 0 or 1; r is 1 or 2; YisZ; Z is: R 1 to R 10 and R 12, R 13 are each independently selected from H and C 1 -C 6 alkyl; R 11 is selected from H, C 1 -C 6 alkyl, C 3 -C 10 cycloalkyl, CF 3, and halogen; ------ is a single bond (C-C) or a double bond (C=C); R 14, R 15 are each independently selected from H, C 1 -C 6 alkyl, and C 3 -C 10 cycloalkyl, or one of R 14, R 15 is L and the other is H; L is L 2, or L 3: R 16, R 17, R 18, R 19, R 20, R 21, R 22, R 23, R 26, R 27, R 30, R 31, R 32, R 33, R 34, R 35, R 36, R 37, R 38, R 39, R 40, R 41, R 42, R 43, R 44, R 45, and R 46 are each independently selected from H and C 1 -C 6 alkyl; R 24, R 25, R 28, R 29 and R 47 are each independently selected from H, halogen, hydroxyl, and (C 1 -C 6)alkoxy; With the provision that when W is H, and R 11 is H, then one of R 14, R 15 cannot be C 1 -C 6 alkyl; With the exclusion of the compound wherein: Y is Z; W is H; ------ is C=C; R 11 is CH 3; R 15 is isopropyl; R 7 is CH 3; and the other radicals R 1 are H; and the stereoisomeric forms, or mixtures of stereoisomeric forms thereof. W is H or -C(=O)-X; X is X a, X b, X c, X d or X e,: R 1a to R 10a, R 1b to R 10b, R 5c to R 10c, R 5d to R 10d, R 5e to R 10e and R 21a, R 21b, R 21c, R 21d and R 11e are each independently selected from H and C 1 -C 6 alkyl; R 11a to R 20a, R 11b to R 20b, R 11c to R 20c, R 11d to R 20d are each independently selected from H, halogen, notably fluorine, hydroxy, and C 1 -C 6 alkoxy; Ar is a phenylene group or a 5 membered heteroarylene group, said phenylene and heterorylene groups being optionally substituted with one to four groups selected from C 1 -C 6 alkyl; n is 0 or 1; m is 0, 1 or 2; o is 0, 1 or 2; provided that m+n+o =3; p is 0 or 1; q is 0 or 1; r is 1 or 2; R 1a to R 10a, R 1b to R 10b, R 5c to R 10c, R 5d to R 10d, R 5e to R 10e and R 21a, R 21b, R 21c, R 21d and R 11e are each independently selected from H and C 1 -C 6 alkyl; R 11a to R 20a, R 11b to R 20b, R 11c to R 20c, R 11d to R 20d are each independently selected from H, halogen, notably fluorine, hydroxy, and C 1 -C 6 alkoxy; Ar is a phenylene group or a 5 membered heteroarylene group, said phenylene and heterorylene groups being optionally substituted with one to four groups selected from C 1 -C 6 alkyl; n is 0 or 1; m is 0, 1 or 2; o is 0, 1 or 2; provided that m+n+o =3; p is 0 or 1; q is 0 or 1; r is 1 or 2; YisZ; Z is: R 1 to R 10 and R 12, R 13 are each independently selected from H and C 1 -C 6 alkyl; R 11 is selected from H, C 1 -C 6 alkyl, C 3 -C 10 cycloalkyl, CF 3, and halogen; ------ is a single bond (C-C) or a double bond (C=C); R 14, R 15 are each independently selected from H, C 1 -C 6 alkyl, and C 3 -C 10 cycloalkyl, or one of R 14, R 15 is L and the other is H; R 1 to R 10 and R 12, R 13 are each independently selected from H and C 1 -C 6 alkyl; R 11 is selected from H, C 1 -C 6 alkyl, C 3 -C 10 cycloalkyl, CF 3, and halogen; ------ is a single bond (C-C) or a double bond (C=C); R 14, R 15 are each independently selected from H, C 1 -C 6 alkyl, and C 3 -C 10 cycloalkyl, or one of R 14, R 15 is L and the other is H; L is L 2, or L 3: R 16, R 17, R 18, R 19, R 20, R 21, R 22, R 23, R 26, R 27, R 30, R 31, R 32, R 33, R 34, R 35, R 36, R 37, R 38, R 39, R 40, R 41, R 42, R 43, R 44, R 45, and R 46 are each independently selected from H and C 1 -C 6 alkyl; R 24, R 25, R 28, R 29 and R 47 are each independently selected from H, halogen, hydroxyl, and (C 1 -C 6)alkoxy; R 16, R 17, R 18, R 19, R 20, R 21, R 22, R 23, R 26, R 27, R 30, R 31, R 32, R 33, R 34, R 35, R 36, R 37, R 38, R 39, R 40, R 41, R 42, R 43, R 44, R 45, and R 46 are each independently selected from H and C 1 -C 6 alkyl; R 24, R 25, R 28, R 29 and R 47 are each independently selected from H, halogen, hydroxyl, and (C 1 -C 6)alkoxy; With the provision that when W is H, and R 11 is H, then one of R 14, R 15 cannot be C 1 -C 6 alkyl; With the exclusion of the compound wherein: Y is Z; W is H; ------ is C=C; R 11 is CH 3; R 15 is isopropyl; R 7 is CH 3; and the other radicals R 1 are H; and the stereoisomeric forms, or mixtures of stereoisomeric forms thereof.