2,2-Dimethyl-propionic acid (3aS,4aS,7R,7aR,7bR)-7a-benzo[1,3]dioxol-5-yl-5-formyl-2,2,3a-trimethyl-octahydro-[1,3]dioxolo[4',5':3,4]cyclopenta[1,2-b]pyrrol-7-yl ester