2-Quinoxalinecarboxmide, N,N'-[2,4,12,15,17,25-hexamethyl-~ 11,24-bis(1-methylethyl)-27-(methylthio)-3,6,10,13,16,19,23~ ,26-octaoxo-9,22-dioxa-28-thia-2,5,12,15,18,25-hexaazabicyclo [12.12.3]nonacosane-7,20-diyl]bis- Antibiotic C638-8, crystalline C 6388 ECHINOMYCIN Echinomycin A NSC13502 Quinomycin A