(1<i>S</i>*,4′<i>S</i>*,5<i>R</i>*)-1-Isobutyl-5-methoxy-2′,3-dimethyl-4,6-dioxa-2-azaspiro[bicyclo[3.2.0]hept-2-ene-7,4′-isoquinoline]-1′,3′(2′<i>H</i>,4′<i>H</i>)-dione
Acta crystallographica. Section E