Linaclotide Impurity 8

(2S,2'S) -2,2'- (((3S,3'S,6R,6'R,9S,9'S,15R,15'R,20R,20'R,23S,23'S,26S,26'S,29R,29'R,32R,32'R,37R,37'R,40S,40'S,45aS,45a'S) -6,6'- (disulfanediylbis (methylene) ) bis (32-amino-40- (2-amino-2-oxoethyl) -26- (2-carboxyethyl) -23- (4-hydroxybenzyl) -9- ((R) -1-hydroxyethyl) -29- (mercaptomethyl) -3-methyl-1,4,7,10,13,22,25,28,31,38,41,47-dodecaoxotetracontahydro-19H-37,20- (epiminomethano) pyrrolo[2,1-s][1,2,27,28]tetrathia[5,8,11,14,17,20,23,32,35,38,41]undecaazacyclotritetracontine-6,15-diyl-15-carbonyl) ) bis (azanediyl) ) bis (3- (4-hydroxyphenyl) propanoic acid)