合成路线1

In a related procedure, malic acid (I) is converted into the O-acetylated monomethyl ester (IV) by a sequence involving O-acetylation with acetic anhydride, followed by dehydration of the resultant O-acetyl malic acid (II) to the cyclic anhydride (III), which undergoes further methanolysis to mono ester (IV). Mono-acid (IV) is then chlorinated with SOCl2, yielding acid chloride (V). Subsequent Li2CuCl4-catalyzed cross-coupling of acid chloride (V) with 2-ethylbutylmagnesium bromide (VI) affords ketone (VII). Elimination of the acetate group of (VII) with triethylamine in toluene leads to the acyl propenoate (VIII). This is subjected to cycloaddition reaction with the lithium derivative of phthalide (IX) producing the dihydroxydihydronaphthalene adduct (X). Finally, dehydration of (X) under acidic conditions furnishes the title compound.