Methyl Ethyl Ketone → (+/-)-cis-7-Methoxy-4,4,15-trimethyl-15,15c-dihydro-4H-benzo[b][1,3]-dioxolo[4',5':3,4]chromeno[6,5-g][1,8]naphthyridin-2,8[3aH]-dione

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Reaction Steps

635.62 mg of N,N′-carbonyldiimidazole are added to a solution of 200 mg of the compound of Example 3 in 90 ml of 2-butanone. The reaction mixture is refluxed for 4 days under argon and then, after cooling, diluted with an aqueous 5% Na2CO3 solution (15 ml) and extracted with ethyl acetate. The organic solutions are combined, dried over anhydrous sodium sulphate, filtered and then evaporated to dryness under reduced pressure. Chromatography on silica gel (dichloromethane and then a gradient of methanol in dichloromethane of from 0.1 to 1.5%) allow 78 mg of the expected product to be isolated.

Provenance & Evidence