Linaclotide Impurity 39

3- ((3S,6R,9S,15R,20R,23S,26S,29R,32R,37R,40S,45aS) -32-amino-40- (2-amino-2-oxoethyl) -15- (((S) -1-ethoxy-3- (4-hydroxyphenyl) -1-oxopropan-2-yl) carbamoyl) -23- (4-hydroxybenzyl) -9- ((S) -1-hydroxyethyl) -3-methyl-1,4,7,10,13,22,25,28,31,38,41,47-dodecaoxotetracontahydro-19H-37,20- (epiminomethano) -6,29- (methanodithiomethano) pyrrolo[2,1-s][1,2,27,28]tetrathia[5,8,11,14,17,20,23,32,35,38,41]undecaazacyclotritetracontin-26-yl) propanoic acid