Patent ID: 7612122

Claim:
A compound of formula (I): where: the substituents R 1 are individually selected from C 1 -C 10 alkyl groups and optionally substituted benzyl groups; the substituents R 2 are individually selected from alkyl groups or, together with the nitrogen atom to which they are attached, represent a nitrogen-containing heterocyclic group; Z is selected from C 6 -C 10 arylene groups and groups of formula —(CHR 3 ) n —, where R 3 is a hydrogen atom, a hydroxy group or a C 1 -C 4 alkyl group, and n is a number from 0 to 6; Y is selected from carbonyl groups and the —CH 2 — group; Q is selected from the residues of mono- or poly-hydroxy compounds having from 1 to 6 hydroxy groups; and x is a number from 1 to 6; and esters thereof.