Dimethyl-3,6-epoxyperhydrophthalic anhydride; (1R,2S,3R,6S)-1,2-Dimethyl-3,6-epoxycyclohexane-1,2-dicarboxylic anhydride; 3a,7a-dimethylhexahydro-4,7-epoxy-2-benzofuran-1,3-dione; (3aR,4S,7R,7aS)-3a,7a-dimethylhexahydro-4,7-epoxy-2-benzofuran-1,3-dione; (3aR,4R,7S,7aR)-3a,7a-dimethylhexahydro-4,7-epoxy-2-benzofuran-1,3-dione; (3aR,7aS)-3a,7a-dimethylhexahydro-4,7-epoxy-2-benzofuran-1,3-dione