aflatoxin aflatoxin B1 exo-8,9-epoxide 6aS,7aS,8aR,8bR)-4-methoxy-2,3,6a,7a,8a,8b-hexahydrocyclopenta[c]oxireno[4',5']furo[3',2':4,5]furo[2,3-h]chromene-1,10-dione C17H12O7 CAS:42583-46-0 [H][C@@]12Oc3cc(OC)c4c5CCC(=O)c5c(=O)oc4c3[C@]1([H])[C@@]1([H])O[C@@]1([H])O2