Studies on the Syntheses of Heterocyclic Compounds. CCIX. Total Syntheses of (±)-Isococlaurine and (-)-Lotusine

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Reductive dealkylation of 1-(4-benzyloxybenzyl)-3, 4-dihydro-6, 7-dimethoxyiso-quinoline (I) with lithium and liquid ammonia gave mainly isococlaurine (II) together with coclaurine (IV) as by-product, which were characterized as their tribenzoate, respectively. Furthermore, reductive methylation of II with formalin and sodium borohydride, followed by methylation with methyl iodide, afforded (±)-lotusine iodide (VII). Furthermore, synthesis and optical resolution of 6-acetoxy-1-(4-benzyloxybenzyl)-1, 2, 3, 4-tetrahydro-2-methylisoquinoline (XII) was carried out to give our expected (+)-N-methylisococlaurine (VI), which was converted into the methiodide (VII), followed by treatment with sliver chloride, to give (-)-lotusine chloride (VIII). The total syntheses of (±)-isococlaurine and (±)-/(-) lotusine halides have been accomplished.