合成路线1

Condensation of 2-bromo-p-toluidine (I) with cyclohexane-1,3-dione (II) gives bromo enaminone (III), which is N-methylated with iodomethane and NaH, affording tertiary enaminone (IV). Treatment of (IV) with triphenylphosphine-palladium acetate complex/NHCO3 or palladium acetate in acetonitrile provides carbazolone (V). Treatment of carbazolone (V) with sodium metal in EtOH/dioxane (or sodium methoxide in 1,2-dimethoxyethane) and diethyl oxalate (VI) provides ethoxallyl derivative (VII), which is then converted into glyoxylic acid lactone (VIII). Coupling of (VIII) with 2-methylimidazol (IX) by means of benzyltriethylammonium chloride in CHCl3/H2O furnishes glyoxylate (X), which is converted into the target product by reaction again with 2-methylimidazol (IX) in dioxane and final treatment with HCl. Alternatively, glyoxylate (X) can be directly obtained from (VIII) by reaction with formaldehyde and 2-methylimidazol (IX) in dioxane.