2-(7,13,16-Tris(2-(tert-butoxy)-2-oxoethyl)-1,10-dioxa-4,7,13,16-tetraazacyclooctadecan-4-yl)acetic acid

2-(7,13,16-Tris(2-(tert-butoxy)-2-oxoethyl)-1,10-dioxa-4,7,13,16-tetraazacyclooctadecan-4-yl)acetic acid,