Butanedioic acid, mono((2-(3-carboxy-1-oxopropoxy)-5-(2-(2,5-dihydro-2-oxo-3-furanyl)ethenyl)decahydro-1,4a-dimethyl-6-methylene-1-naphthalenyl)methyl) ester, monopotassium salt, (1R-(1alpha,2alpha,4aalpha,5alpha(E),8abeta))-