Long-acting contraceptive agents: esters of norethisterone with alpha- and/or beta-chain branching.

The synthesis of eighteen esters of norethisterone (17 alpha-ethynyl-17 beta-hydroxyestr-4-en-3-one) is described. These all possess some form of alpha- and/or beta-substitution in the ester side-chain. The work was undertaken in order to evaluate any long-acting fertility control effect intrinsic in such compounds. A pentamethyl disiloxy ether was also included in the group of substances prepared for testing because of its similar substitution pattern.