4,8-Dioxa-3,9-dithia-2,10-diazaundecanedioic acid,6,6-bis(7-methyl-3,3-dioxido-5-oxo-2,6-dioxa-3-thia-4-azaoct-1-yl)-,bis(1-methylethyl) ester, 3,3,9,9-tetraoxide