Cyclo[L-Arg-L-Trp-L-Phe-L-Trp-[[1-amino*-3-(2-guanidinoethyl)cyclobutyl]carbonyl]-L-Arg-]

Cyclo[L-Arg-L-Trp-L-Phe-L-Trp-[[1-amino*-3-(2-guanidinoethyl)cyclobutyl]carbonyl]-L-Arg-]