(1R,1′R,2R,2′R,3R,3′R,4R,4′R,6S,6′S,8S,8′S,9R,9′R,10S,10′S,11S,11′S,13S,13′S,17S)-2,2′,3,3′,6,6′-Hexahydroxy-5,5,5′,5′,9,9′-hexamethyl-15′-oxo-18-oxaspiro[pentacyclo[11.6.1.0~1,10~.0~4,9~.0~14,19~]ico sane-17,14′-tetracyclo[11.2.1.0~1,10~.0~4,9~]hexadecane]-14(19)-ene-8,8′,11,11′-tetrayl tetraacetate