18,19-DINORPREGNA-5(10),15-DIEN-20-YN-3-ONE, 13-ETHYL-17-HYDROXY-, CYCLIC 1,2-ETHANEDIYL ACETAL, (17.ALPHA.)-
18,19-dinorpregna-5(10),15-dien-20-yn-3-one, 13-ethyl-17-hydroxy-, cyclic 1,2-ethanediyl acetal, (17.alpha.)-