合成路线1

The bromination of 3,4-dimethoxybenzaldehyde (I) with Br2 in methanol gives the 6-bromo-3,4-dimethoxybenzaldehyde (II), which is regioselectively demethylated with conc. H2SO4 yielding 6-bromo-3-hydroxy-4-methoxybenzaldehyde (III). The reductocondensation of (III) with 2-(4-hydroxyphenyl)ethylamine (IV) by means of NaBH4 in ethanol affords the secondary amine (V), which is formylated with ethyl formate and formic acid in dioxane furnishing the formamide (VI). The oxidative cyclization of (VI) by means of potassium ferricyanide and K2CO3 in toluene/water gives the (+/-)-bromoformylnarwedine (VII), which is protected with propyleneglycol (VIII) and TsOH in hot toluene yielding the ketal (IX). The reduction of the formyl group of (IX) with LiAlH4 in THF affords racemic narwedine (X), which is submitted to a crystallization-induced chiral transformation using a catalytic amount of seed crystals of (-)-narwedine in refluxing ethanol containing TEA, an 80% of (-)-narwedine (XI) is obtained. Finally, this compound is stereoselectively reduced to the target compound by means of L-selectride in THF.