Sodium (4aR,6aR,7R,10aS,10bR)-6a,10b-dimethyl-8-methylene-7-((E)-2-(2-oxo-2,5-dihydrofuran-3-yl)vinyl)decahydro-1H-naphtho[2,1-d][1,3,2]dioxaphosphinin-3-olate 3-oxide