(rac-5RS,7RS,8SR)-Spiro­[7-methoxy­carbonyl-1-aza-3-thia­bi­cyclo­[3.3.0]­octane-8,1′-ace­naphthyl­en]-2′-one

The title compound, C₁₉H₁₇NO₃S, crystallizes in the monoclinic space group P2₁/c, with four mol­ecules in the unit cell. The structure contains a spiro-carbon connecting a bi­cyclo-octane group, consisting of two fused five-membered rings, to an ace­naphthyl­ene moiety. The five-membered ring containing the S atom is in an envelope conformation. The conformation of the other five-membered ring of the bi­cyclo-octane moiety is close to a half-chair. The methoxycarbonyl group is equatorially substituted.