4,10-Dioxa-tricyclo[5.2.1.0~2,6~]dec-8-ene-3,5-dione AIDS-189638 AIDS189638 exo-3,6-Epoxy-1,2,3,6-tetrahydrophthalic anhydride treated BSA exo-3,6-Epoxy-1,2,3,6-tetrahydrophthalic anhydride treated bovine serum albumin