(2R,7aR)-2-[(4-chlorophenoxy)methyl]-7a-(4-methoxyphenyl)-2,3,6,7-tetrahydropyrrolo[5,1-b][1,3]oxazol-5-one (2R,7aR)-2-[(4-chlorophenoxy)methyl]-7a-(4-methoxyphenyl)-2,3,6,7-tetrahydropyrrolo[5,1-b]oxazol-5-one