Phthalic Anhydride → 5-(2-Carboxybenzoyloxy)-4-methoxy-2,6,6-trimethyl-2-cyclohepten-1-one

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Reaction Conditions

Reaction Steps

To a solution of 5-hydroxy-4-methoxy-2,6,6-trimethyl-2-cyclohepten-1-one (AU154) obtained in Example 4 (1.98 g, 10 mM) in pyridine (10 ml), phthalic anhydride (1.78 g, 12 mM) and dimethyl aminopyridine (0.05 g) were added and warmed to 90° C. for three hours, left to cool, poured onto ice-water, alkalified with potassium carbonate and extracted with ethyl acetate. The aqueous layer was acidified with hydrochloric acid and extracted with ethyl acetate, washed with brine, dried over magnesium sulfate, filtered, and concentrated. The residue was crystallized from a mixed solvent of ethyl acetate and hexane to obtain 1.80 g (53%) of 5-(2-carboxybenzoyloxy)-4-methoxy-2,6,6-trimethyl-2-cyclohepten-1-one (AU218) as colorless plates. Melting point: 158.0° to 158.5° C.

Provenance & Evidence