合成路线1

Ketoester (II) was prepared by condensation of dimethyl carbonate with 5-methoxy-2-tetralone (I) in the presence of NaOMe. The alkylation of (II) with allyl bromide using two equivalents of LDA at -78 C proceeded selectively on the C-3 position to give (III). Further decarbomethoxylation of (III) was carried out with LiCl in moist DMSO at high temperature, and the resulting ketone (IV) was converted to ethylene ketal (V) with ethylene glycol and p-TsOH. Then, hydroboration of (V) with disiamyl borane (VI) in cold THF, followed by oxidation of borane (VII) with H2O2-NaOH furnished the primary alcohol (VIII). After Jones oxidation of alcohol (VIII), the resulting acid (IX) was esterified with MeOH and H2SO4 to give ketoester (X). Subsequent cyclization of (X) with benzylamine (XI) and AcOH in refluxing benzene afforded the intermediate tricyclic enamide (XII), which was sequentially reduced with LiAlH4 to enamine (XIII), and then with NaBH4 in the presence of AcOH to furnish a mixture of cis and trans octahydrobenzo[g]quinolines (XIV). Separation of the major trans isomer by flash chromatography was followed by hydrogenolysis of the benzyl group over Pd/C, yielding the secondary amine (XV), whitch was N-alkylated with propargyl bromide (XVI) in hot DMF to give (XVII).