C(=O)[CH2:2][CH:3]([CH3:5])[CH3:4].N1CCOCC1.C(O)C.[CH3:16][O:17][C:18]([C:20]1[C:24](=O)O[C:22]2=[CH:26][CH:27]=[C:28]([CH:31]([CH3:33])[CH3:32])[CH:29]=[CH:30][C:21]=12)=[O:19]>C1(C)C=CC=CC=1>[CH3:16][O:17][C:18]([C:20]1[C:21]2[C:22]([CH:26]=[CH:27][C:28]([CH:31]([CH3:33])[CH3:32])=[CH:29][CH:30]=2)=[C:2]([CH:3]([CH3:5])[CH3:4])[CH:24]=1)=[O:19]Isovaleraldehyde (5.16 g) and morpholine (4.36 g) are added to ethanol (14 ml) and then 3-methoxycarbonyl-6-isopropyl-2H-cyclohepta[b]furan-2-one (5) (2.46 g) is added thereto. The obtained mixture is heated under reflux for 16 hours, and then the solvent is distilled off under reduced pressure to give an oily material. The obtained oily material is dissolved in toluene (20 ml), washed twice with water (20 ml) and 4 times with 1N HCl (20 ml), and further, twice with water (40 ml). The obtained toluene layer is passed through silica gel column (1.05 kg), the column is eluted with toluene. From the eluted parts including the product (24), the solvent is distilled off under reduced pressure to give the compound (24) as a purple oily material in a yield of 2.08 g, 76.%.
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