4,6-Dioxatricyclo(3.3.1.0(2,7))nonane, 1,3,3-trimethyl-, (+-)- 4,9-Dioxatricyclo(3.3.1.0(2,7))nonane, 3,3,7-trimethyl-, (1alpha,2beta,5alpha,7beta)- (+-)- 71899-16-6