Wan A S, Ngiam T L, Leung S L, Go M L, Francisco C G, Freire R, Hernandez R, Salazar J A, Suarez E, García G A
Steroids. 1983 Mar;41(3):339-48. doi: 10.1016/0039-128x(83)90105-8.
Esters of levonorgestrel (13 beta-ethyl-17 beta-ethynyl-17 beta-hydroxygon-4-en-3-one) with a variety of unsaturated carboxylic acids have been synthesized for evaluation as potential long-acting, injectable contraceptive agents.