prov:value
| - each of R4 and R5, independently, is selected from methyl, ethyl, linear or branched C3-24 alkyl, C7-24 alkaryl, C5-24 aralkyl, C6-24 cycloalkyl, C6-24 aryl and the groups of formula a) and b) ##STR2## provided only one of R4 and R5 is a group of formula b); or both groups R4 and R5 together form a group of formula c); ##STR3## in which R4a and R5a, independently, are selected from --R10, and a gr
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