[7-[2-[2-(8-thia-7,9-diazabicyclo[4.3.0]nona-3,5,9-trien-7-yl)ethyldis ulfanyl]ethyl]-8-thia-7,9-diazabicyclo[4.3.0]nona-3,5,9-trien-2-yl]met hanamine