If R26 is the radical of an alcohol, R26 is preferably linear or branched C3 -C20 alkyl or -alkenyl, C3 -C8 --, particularly C5 -C6 cycloalkyl, --CH2 --(C5 -C6 cycloalkyl), C6 -C10 aryl, in particular phenyl or naphthyl, or C7 -C16 aralkyl, in particular benzyl or 1-phenyl-2-ethyl.