合成路线1

Lithiation of 1,3-dimethoxybenzene (I), followed by addition of triisopropyl borate to the resultant lithio derivative (II) provided boronic acid (III). This was subjected to palladium-catalyzed Suzuki coupling with methyl 5-nitro-2-bromobenzoate (IV) to afford the biphenyl compound (V). Cleavage of the methyl ethers of (V) using boron tribromide gave rise to the tricyclic lactone (VI). After methylation of the hydroxyl group of (VI) with iodomethane and cesium carbonate, the resultant nitro derivative (VII) was reduced to amine (VIII) by catalytic hydrogenation. Iodine-catalyzed condensation of amine (VIII) with acetone at 105 ºC in a sealed vessel furnished the benzopyranoquinoline system (IX). The lactone function of (IX) was then reduced to the corresponding lactol (X) by means of DIBAL in cold dichloromethane. Subsequent treatment of (X) with methanol and p-toluenesulfonic acid produced acetal (XI). The acetal methoxy group of (XI) was finally displaced with allyl trimethylsilane (XII) in the presence of boron trifluoride etherate to furnish the title allyl derivative