Compound 12

(S)-N-((S)-1-((2-Amino-2-oxoethyl)amino)-4-methyl-1-oxopentan-2-yl)-1-((3R,6S,9S,12S,15S,18S)-18-amino-6-(2-amino-2-oxoethyl)-9-(3-amino-3-oxopropyl)-12-((S)-sec-butyl)-15-(4-hydroxybenzyl)-5,8,11,14,17-pentaoxo-1-selena-4,7,10,13,16-pentaazacycloicosane-3-carbonyl)pyrrolidine-2-carboxamide

From: Selenoether oxytocin analogues have analgesic properties in a mouse model of chronic abdominal pain