{(E)-(R)-3-[(1R,3aR,6aS)-1-(4-Methoxy-benzyloxy)-2,2-dimethyl-5-oxo-hexahydro-pentalen-3a-yl]-but-1-enyl}-phosphonic acid diethyl ester

rac-diethyl ((R,E)-3-((3aS,4R,6aR)-4-((4-methoxybenzyl)oxy)-5,5-dimethyltetrahydro-1H-spiro[pentalene-2,2'-[1,3]dioxolan]-6a(3H)-yl)but-1-en-1-yl)phosphonate