Crystal structures of 2′-benzoyl-1′-(4-methylphenyl)-1,1′,2,2′,5′,6′,7′,7a′-octahydrospiro[indole-3,3′-pyrrolizin]-2-one and 2′-(4-bromobenzoyl)-1′-(2-chlorophenyl)-1,1′,2,2′,5′,6′,7′,7a′-octahydrospiro[indole-3,3′-pyrrolizin]-2-one