Studies on Ergot Alkaloids and Related Compounds. XII. Syntheses of Ethyl 4-Methyl-2,3,4,4α, 5,6-hexahydrobenzo[f]quinoline-2-carboxylate and its Dihydro Derivative

The syntheses and stereochemistries of ethyl 4-methyl-2,3,4,4α, 5,6-hexahydrobenzo-[f]quinoline-2-carboxylate (XII) and its dihydro derivative (XIII) were described. The Mannich reaction of ethl β-oxo-3,4-dihydro-1-naphthalenepropionate (VII), which was prepared by condensation of 1-acetyl-3,4-dihydronaphthalene (V) with diethyl carbonate, gave ethyl 1-oxo-4-methyl-trans(4α : 10b)-1,2,3,4,4α, 5,6,10b-octahydrobenzo[f]quinoline-2-carboxylate (VIII) and compound (VII). Sodium borohydride reduction, followed by dehydration, converted VIII into XII, which was hydrogenated over platinum oxide to XIII. Compounds (XII, XIII, and VII) showed considerably potent oxytocic activity.