134790-35-5 Boc-cyclo(glu-pro-asn-lys)ome Butyloxycarbonyl-cyclo(glutamyl-prolyl-asparaginyl-lysyl) methyl ester L-Lysine, N-((1,1-dimethylethoxy)carbonyl)-L-alpha-glutamyl-L-prolyl-Lasparaginyl-, 4-methyl ester, cyclic (1-4)- peptide