{(1aS,8S,8aR,8bR)-6-amino-8a-methoxy-5-methyl-1-[(4-methylphenyl)sulfonyl]-4,7-dioxo-1,1a,2,4,7,8,8a,8b-octahydroazireno[2',3':3,4]pyrrolo[1,2-a]indol-8-yl}methyl carbamate