Ethyl 7′-(6-benzyloxy-2,2-dimethyltetrahydrofuro[3,2-d][1,3]dioxol-5-yl)-2-oxo-5′,6′,7′,7a'-tetrahydro-1′H,2H-spiro[acenaphthylene-1,5′-pyrrolo[1,2-c][1,3]thiazole]-6′-carboxylate