(4’R,4a’S,7a’R,12b’S)-3′-allyl-4a’-hydroxy-2′,3′,4′,4a’,5′,6′-hexahydro-1’H,7a’H-spiro[[1,3]dioxolane-2,7′-[4,12]methanobenzofuro[3,2-e]isoquinolin]-9′-yl diethylcarbamate