合成路线1

The bromination of 3,4-dimethoxybenzaldehyde (I) with Br2 in acetic acid gives 2-bromo-4,5-dimethoxybenzaldehyde (II), which is selectively demethylated with H2SO4 yielding 2-bromo-5-hydroxy-4-methoxybenzaldehyde (III). The reductocondensation of (III) with 2-(4-hydroxyphenyl)ethylamine (IV) by means of NaBH4 affords the secondary amine (V), which is formylated with ethyl formate in dioxane/DMF giving the formamide (VI). The cyclization of (VI) by means of potassium hexacyanoferrate (III) and K2CO3 in hot toluene yields racemic N-formylbromonarwedine (+/-)(VII), which is reduced with lithium tri-tert-butoxyaluminum hydride furnishing a mixture of N-demethylbromogalanhamine (+/-)(VIII) and N-demethylepibromogalanthamine (+/-)(IX). After chromatographic separation of the two racemic epimers, resolution of racemic (+/-)(VIII) is carried out employing di-p-toluoyl tartaric acid to afford the required levo isomer. Alkylation of (-)(VIII) with 1-(3-chloropropyl)piperidine (X) gives (XI), which is finally converted to the title compound by reductive debromination in the presence of Zn and CaCl2.