Patent ID: 8563489

Claim:
A compound of structure (I) having the general formula: wherein R 1 and R 2 are the same and are selected from the group consisting of n-propyl, 1-methylethyl, n-butyl, isobutyl, sec-butyl, 1,3-dimethylbutyl, n-pentyl, isopentyl, hexyl, 2-methyl-propenyl, cyclopentyl, cyclohexyl, wherein R 3 and R 4 are independently selected from the group consisting of C 1 -C 20 alkyl, 2-methyl-propenyl, benzyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl; and wherein R 5 and R 6 are independently selected from the group consisting of hydrogen, C 1 -C 20 alkyl, 2-methyl-propenyl, benzyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl benzyl.