The synthesis of and guinea pig contragestational screening data for several oxepane and 3, 8-dioxabicyclo [3.2. lloctane analogues of zoapatanol (1) are described and their structure- activity relationships discussed. Conversion of the 5-keto group on the nonenyl side chain of 1 into a hydroxyl function enhanced the potency. Further significant enhancement in the potency was realized with the transformation of several oxepanes into the 3, 8- ...