Aztequine (I), m.p. 176°, is an alkaloid isolated in 1948 by Pallares and Garza from the leaves of a Mexican Magnoliaceae plant, yoloxochitl (
Talauma mexicana DON.). As a preliminary to the total synthesis of I, synthesis of tetramethylaztequine (II) was attempted. In general, presence of an electron-attracting group like nitro in the position
ortho or para to the halogen results in smooth progress of the Ullmann reaction, with a good yield. Therefore, 3-nitro-4-bromobenzaldehyde, obtained by nitration of 4-bromobenzaldehyde, and vanillin were submitted to the Ullmann reaction and 3-nitro-4-(2-methoxy-4-formylphenoxy)-benzaldehyed was obtained. Its reduction with sodium borohydride to the dialcohol, followed by chlorination and derivation to the dinitrile, and hydrolysis with conc. hydrochloric acid afforded the objective dihomo acid. Its fusion with homoveratrylamine or its Schotten-Baumann reaction gave the corresponding diamide (XXVII) whose Bischler-Napieralski reaction produced bis (3, 4-dihydroisoquinoline) derivative. Catalytic reduction of its methiodide (XXIX) finally afforded
rac-3-amino-3′-methoxy-4, 4′-bis (2-methyl-6, 7-dimethoxy-1, 2, 3, 4-tetrahydro-1-isoquinolylmethyl)-diphenyl ether (XXXI). Attempt to diazotize XXXI to change the amino group into hydroxyl and its methylation to obtain II did not materialize.
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