A mixture of 5-[4-(cyclopropylsulfonyl)phenyl]-1-[5-(1-hydroxyethyl)-1,3-thiazol-2-yl]-6-(tetrahydro-2H-pyran-4-yl)hexane-1,4-dione (1.36 g), ammonium acetate (1.33 g) and acetic acid (15 mL) was stirred at 100° C. for 2 hr. The reaction mixture was neutralized with 8M aqueous sodium hydroxide solution, and extracted with ethyl acetate. The ethyl acetate layer was concentrated, 2M aqueous sodium hydroxide solution (4 mL), tetrahydrofuran (8 mL) and methanol (8 mL) were added to the residue, and the mixture was stirred with heating under reflux for 2 hr. Water was added to the reaction mixture, and the mixture was extracted with ethyl acetate. The ethyl acetate layer was washed with saturated brine, dried (MgSO4) and concentrated. The residue was subjected to basic silica gel column chromatography, and the title compound (0.43 g, yield 33%) was obtained as a yellow amorphous solid from a fraction eluted with ethyl acetate-hexane (4:1, volume ratio). MS: 487 (MH+).
