A compound of formula I or formula II wherein R 1 is a group of formula III hydrogen, C 1 -C 18 alkyl, C 3 -C 18 alkenyl, C 3 -C 12 cycloalkyl, C 5 -C 8 cycloalkenyl, C 6 -C 10 bicycloalkyl, C 3 -C 18 alkynyl, C 6 -C 10 aryl, C 7 -C 9 aralkyl or C 7 -C 20 aralkyl substituted by C 1 -C 4 alkyl or C 6 -C 10 aryl; R 4 is a group of formula IV hydrogen, C 1 -C 18 alkyl, C 3 -C 18 alkenyl, C 3 -C 12 cycloalkyl, C 5 -C 8 cycloalkenyl, C 6 -C 10 bicycloalkyl, C 3 -C 18 alkynyl, C 6 -C 10 aryl, C 7 -C 9 aralkyl or C 7 -C 20 aralkyl substituted by C 1 -C 4 alkyl or C 6 -C 10 aryl; R 2, R 3, R 5 and R 6 are each independently from each other C 1 -C 18 alkyl, C 3 -C 18 alkenyl, C 3 -C 12 cycloalkyl, C 5 -C 8 cycloalkenyl, C 6 -C 10 bicycloalkyl, C 3 -C 18 alkynyl, C 6 -C 10 aryl, C 7 -C 9 aralkyl or C 7 -C 20 aralkyl substituted by C 1 -C 4 alkyl or C 6 -C 10 aryl; Z 1, Z 2, Z 3, Z 4, Z 11 and Z 12 are each independently from each other C 1 -C 18 alkyloxy, C 3 -C 18 alkenyloxy, C 3 -C 18 alkynyloxy, C 6 -C 10 aryloxy, C 7 -C 9 aralkyloxy or C 7 -C 20 aralkyloxy substituted by C 1 -C 4 alkyl or C 6 -C 10 aryl; X 1 is C 2 -C 12 alkylene or C 3 -C 12 alkylene substituted by hydroxyl; or R 7 is a group of formula V hydrogen, C 1 -C 18 alkyl, C 3 -C 18 alkenyl, C 3 -C 12 cycloalkyl, C 5 -C 8 cycloalkenyl, C 6 -C 10 bicycloalkyl, C 3 -C 18 alkynyl, C 6 -C 10 aryl, C 7 -C 9 aralkyl or C 7 -C 20 aralkyl substituted by C 1 -C 4 alkyl or C 6 -C 10 aryl; R 10 is a group of formula VI hydrogen, C 1 -C 18 alkyl, C 3 -C 18 alkenyl, C 3 -C 12 cycloalkyl, C 5 -C 8 cycloalkenyl, C 6 -C 10 bicycloalkyl, C 3 -C 18 alkynyl, C 6 -C 10 aryl, C 7 -C 9 aralkyl or C 7 -C 20 aralkyl substituted by C 1 -C 4 alkyl or C 6 -C 10 aryl; R 13 is a group of formula VII hydrogen, C 1 -C 18 alkyl, C 3 -C 18 alkenyl, C 3 -C 12 cycloalkyl, C 5 -C 8 cycloalkenyl, C 6 -C 10 bicycloalkyl, C 3 -C 18 alkynyl, C 6 -C 10 aryl, C 7 -C 9 aralkyl or C 7 -C 20 aralkyl substituted by C 1 -C 4 alkyl or C 6 -C 10 aryl; R 8, R 9, R 11, R 12, R 14 and R 15 are each independently from each other C 1 -C 18 alkyl, C 3 -C 18 alkenyl, C 3 -C 12 cycloalkyl, C 5 -C 8 cycloalkenyl, C 6 -C 10 bicycloalkyl, C 3 -C 18 alkynyl, C 6 -C 10 aryl, C 7 -C 9 aralkyl or C 7 -C 20 aralkyl substituted by C 1 -C 4 alkyl or C 6 -C 10 aryl; Z 5, Z 6, Z 7, Z 8, Z 9, Z 10, Z 13, Z 14 and Z 15 are each independently from each other C 1 -C 18 alkyloxy, C 3 -C 18 alkenyloxy, C 3 -C 12 cycloalkyloxy, C 5 -C 8 cycloalkenyloxy, C 6 -C 10 bicycloalkyloxy, C 3 -C 18 alkynyloxy, C 6 -C 10 aryloxy, C 7 -C 9 aralkyloxy or C 7 -C 20 aralkyloxy substituted by C 1 -C 4 alkyl or C 6 -C 10 aryl; X 2, X 3 and X 4 are each independently from each other C 2 -C 12 alkylene or C 3 -C 12 alkylene substituted by hydroxyl. R 1 is a group of formula III hydrogen, C 1 -C 18 alkyl, C 3 -C 18 alkenyl, C 3 -C 12 cycloalkyl, C 5 -C 8 cycloalkenyl, C 6 -C 10 bicycloalkyl, C 3 -C 18 alkynyl, C 6 -C 10 aryl, C 7 -C 9 aralkyl or C 7 -C 20 aralkyl substituted by C 1 -C 4 alkyl or C 6 -C 10 aryl; R 4 is a group of formula IV hydrogen, C 1 -C 18 alkyl, C 3 -C 18 alkenyl, C 3 -C 12 cycloalkyl, C 5 -C 8 cycloalkenyl, C 6 -C 10 bicycloalkyl, C 3 -C 18 alkynyl, C 6 -C 10 aryl, C 7 -C 9 aralkyl or C 7 -C 20 aralkyl substituted by C 1 -C 4 alkyl or C 6 -C 10 aryl; R 2, R 3, R 5 and R 6 are each independently from each other C 1 -C 18 alkyl, C 3 -C 18 alkenyl, C 3 -C 12 cycloalkyl, C 5 -C 8 cycloalkenyl, C 6 -C 10 bicycloalkyl, C 3 -C 18 alkynyl, C 6 -C 10 aryl, C 7 -C 9 aralkyl or C 7 -C 20 aralkyl substituted by C 1 -C 4 alkyl or C 6 -C 10 aryl; Z 1, Z 2, Z 3, Z 4, Z 11 and Z 12 are each independently from each other C 1 -C 18 alkyloxy, C 3 -C 18 alkenyloxy, C 3 -C 18 alkynyloxy, C 6 -C 10 aryloxy, C 7 -C 9 aralkyloxy or C 7 -C 20 aralkyloxy substituted by C 1 -C 4 alkyl or C 6 -C 10 aryl; X 1 is C 2 -C 12 alkylene or C 3 -C 12 alkylene substituted by hydroxyl; or R 7 is a group of formula V hydrogen, C 1 -C 18 alkyl, C 3 -C 18 alkenyl, C 3 -C 12 cycloalkyl, C 5 -C 8 cycloalkenyl, C 6 -C 10 bicycloalkyl, C 3 -C 18 alkynyl, C 6 -C 10 aryl, C 7 -C 9 aralkyl or C 7 -C 20 aralkyl substituted by C 1 -C 4 alkyl or C 6 -C 10 aryl; R 10 is a group of formula VI hydrogen, C 1 -C 18 alkyl, C 3 -C 18 alkenyl, C 3 -C 12 cycloalkyl, C 5 -C 8 cycloalkenyl, C 6 -C 10 bicycloalkyl, C 3 -C 18 alkynyl, C 6 -C 10 aryl, C 7 -C 9 aralkyl or C 7 -C 20 aralkyl substituted by C 1 -C 4 alkyl or C 6 -C 10 aryl; R 13 is a group of formula VII hydrogen, C 1 -C 18 alkyl, C 3 -C 18 alkenyl, C 3 -C 12 cycloalkyl, C 5 -C 8 cycloalkenyl, C 6 -C 10 bicycloalkyl, C 3 -C 18 alkynyl, C 6 -C 10 aryl, C 7 -C 9 aralkyl or C 7 -C 20 aralkyl substituted by C 1 -C 4 alkyl or C 6 -C 10 aryl; R 8, R 9, R 11, R 12, R 14 and R 15 are each independently from each other C 1 -C 18 alkyl, C 3 -C 18 alkenyl, C 3 -C 12 cycloalkyl, C 5 -C 8 cycloalkenyl, C 6 -C 10 bicycloalkyl, C 3 -C 18 alkynyl, C 6 -C 10 aryl, C 7 -C 9 aralkyl or C 7 -C 20 aralkyl substituted by C 1 -C 4 alkyl or C 6 -C 10 aryl; Z 5, Z 6, Z 7, Z 8, Z 9, Z 10, Z 13, Z 14 and Z 15 are each independently from each other C 1 -C 18 alkyloxy, C 3 -C 18 alkenyloxy, C 3 -C 12 cycloalkyloxy, C 5 -C 8 cycloalkenyloxy, C 6 -C 10 bicycloalkyloxy, C 3 -C 18 alkynyloxy, C 6 -C 10 aryloxy, C 7 -C 9 aralkyloxy or C 7 -C 20 aralkyloxy substituted by C 1 -C 4 alkyl or C 6 -C 10 aryl; X 2, X 3 and X 4 are each independently from each other C 2 -C 12 alkylene or C 3 -C 12 alkylene substituted by hydroxyl.