The molecule is a guanidinium ion resulting from the protonation of the guanidino group of Ac-(D)Phe-Pro-boroArg-OH. The major species at pH 7.3. It is a conjugate acid of an Ac-(D)Phe-Pro-boroArg-OH.
[(4R)-4-[[(2S)-1-[(2R)-2-acetamido-3-phenylpropanoyl]pyrrolidine-2-carbonyl]amino]-4-boronobutyl]-(diaminomethylidene)azanium