Synthetic studies in the field of the curare alkaloids

Abstract

By oxidation and the identification of the oxidation products, it has been shown that the β-[4-(2″-alkoxy-5″-alkoxycarbonylmethylphenoxy)-3-methoxyphenyl] ethylamides of 4′-benzyloxyphenylacetic acid obtained previously and differing in their physicochemical properties are based on the same skeleton and differ only in their spatial configuration, since on Bischler-Napieralski cyclization they give isomeric dihydroisoquinoline compounds. The structure of the latter was established by oxidation to the isomeric acids 2,2′-dimethoxy-3,4,5′-tricarboxy(diphenyl ether) and 2,2′-dimethoxy-4,5,5′-tricarboxy-(diphenyl ether); the latter is identical with the compound obtained by the degradation of the methyl ester of natural tubocurarine. 1-(4′Benzyloxybenzyl)-6-methoxy-7-(2′-methoxy-5″-methoxycarbonyl methylphenoxy)-N-methyl-1,2,3,4-tetrahydroisoquinoline and a compound isomeric with it have also been synthesized, and the former has been shown to be identical with a substance obtained by independent synthesis from the 4′-benzyl ether of N-methylcoclaurine. During the synthesis of the latter it was shown that cyclization takes place unambiguously without the formation of isomeric compounds.