4-[(3bS,4aS,5aR,6R,6aS,7aS,7bS,8aS,8bS)-6a-Isopropyl-8b-methyl-1-oxo-1,3,3b,4,4a,6,6a,7a,7b,8b,9,10-dodecahydrotrisoxireno[6,7:8a,9:4b,5]phenanthro[1,2-c]furan-6-yloxy]-4-oxobutyric acid sodium salt