The structure of 6,6-dimethyl-4-trichloromethyl-3-oxabicyclo[3.1.0]hexan-2-
one-1-carboxylic acid ethyl ester (C11H13Cl3O4), a potential pyrethroid-typ
e intermediate, is presented. It is dominated by the interplanar angle [70.
1(3)degrees] formed by the lactone and the cyclopropane rings of the molecu
le. A structural comparison with other related published structures is also
presented.