Furo[2',3':5,6]cyclohepta[1,2-c]pyran-2(3H)-one,5-ethoxy-3a,4,4a,5,8a,9,10,10a-octahydro-4a,9-dimethyl-3-methylene-, [3aR-(3aa,4ab,5a,8aa,9a,10aa)]-