Reaction of 1-ethoxycarbonylmethyl-6, 7-dimethoxy-1, 2, 3, 4-tetrahydroisoquinoline with urea gave 2, 4-dioxo-9, 10-dimethoxy-1, 2, 3, 4, 6, 7-hexahydro-11b
H-pyrimido [4, 3-
a]-isoquinoline (II), which was reduced to 9, 10-dimethoxy-1, 2, 3, 4, 6, 7-hexahydro-11b
H-pyrimido [4, 3-
a] isoquinoline (III) with lithium aluminum hydride at 60°, but to 1-methyhlaminoethyl-6, 7-dimethoxy-1, 2, 3, 4-tetrahydroisoquinoline (IV) at 80°. Reductive methylation of (III), suffering fission of the hydropyrimidine ring, with formaldehyde and formic acid, or by formaldehyde and hydrogenation over Raney nickel under high pressure, gave 1-(2-dimethylaminoethyl)-2-methyl-6, 7-dimethoxy-1, 2, 3, 4-tetrahydroisoquinoline (V), identical with the compound obtained by the reaction of (IV) with formaldehyde and formic acid. Hydrolysis of (III), with mineral acid gave 1-(2-aminoethyl)-6, 7-dimethoxy-1, 2, 3, 4-tetrahydroisoquinoline (VIII), which was reversibly converted into (III) on treatment with formaldehyde. Reaction of (IV) with formaldehyde or vanillin gave 3-methyl-9, 10-dimethoxy-1, 2, 3, 4, 6, 7-hexahydro-11b
H-pyrimido [4, 3-a] isoquinoline (VI), the N-methyl compound of (III), or 3-methyl-4-(3′-methoxy-4′-hydroxyphenyl)-9, 10-dimethoxy-1, 2, 3, 4, 6, 7-hexahydro-11b
H-pyrimido [4, 3-a] isoquinoline (VII). The products, (VI) and (VII), were also hydrolysed into the starting material (IV), respectively liberating formaldehyde and vanillin. The compound (III), a hydropyrimidine derivative, was readily acylated or tosylated without suffering fission of the ring, which differs from an imidazolidine derivative. Physiological actions of (II), (III), (IV), (V), (VI), and (VII) are to be examined.
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