“…In Table 1 the most stable members of each family are reported while Table 2 shows for the 13-ethylsteroids 1-3 all the members of the family to which the global minima belong. The preferred conformation of compounds 1-5, located in the present study, corresponds, in the tetracyclic skeleton, to the geometry already determined at the same level of calculations for progesterone 6 [10]. In fact, it can be seen from Table 1 that the most stable conformation of each compound (1A, 2A, 3A, 4A, 5A, and 6A) show very close values of torsional angles and puckering coordinates.…”