is particularly preferably ethylene h r 1 is c 1 c 6 alkylene nr 10 u2014 co u2014 r 11 where r 2 r 3 r 4 r 10 and c 1 c 6 alkylene have the meanings indicated above under g and r 1 is c 1 c 6 alkyl benzyl phenylethyl ch u2550 chph or ch ph 2 i r 1 is c 1 c 6 alkylene nr 10 u2014 so 2 u2014 r 12 where r 2 r 3 r 4 r 10 and c 1 c 6 alkylene have the meanings indicated above under g and r 12 is furyl thienyl or naphthyl j r 1 is c 1 c 6 alkylene nr 10 u2014 co u2014 r 11 where r 2 r 3 r 4 r 10 and c 1 c 6 alkylene have the meanings indicated above under g and r 11 is phenyl which optionally has one two or three substituents which independently of one another are selected from halogen no 2 cf 3 c 1 c 6 alkyl and nhcoc 1 u2014 c 3 alkyl or c 1 c 6 alkyl benzyl or naphthyl k r 1 is u2014 ch 2 u2014 r 7 r 7 is coor 8 r 8 is h or c 1 c 6 alkyl r 2 is h or c 1 c 6 alkyl and at least one of the radicals r 3 and r 4 is oc 1 u2014 c 6.