Abstract
By catalytic reduction with PtO2 as a catalyst in glacial acetic acid solution at ordinary temperature, dictamnine (I), isodictamnine (V), nordictamnine (VI), and skimmianine (IV) absorb 2 moles of hydrogen to yield C12H13NO2, colorless silky needles, m.p. 186-187°, C12H13NO2, long pillars, m.p. 185°, C11H11NO2, prisms, m.p. 262° (monoacetate, white microneedles, m.p. 247-248°), and C14H17NO4, prisms, m.p. 183°, repectively. The reduction product of (VI) was proved to be identical with 2, 4-dihydroxy-3-ethyl-quinoline, m.p. 262° (monoacetate, m.p. 248°), which was synthetically prepared from methyl N-butyrylanthranilate (pillars, m.p. 71°) by Camps' quinoline synthesis. The catalytic hydrogenation of 2, 3-furo-(2′, 3′)-quinoline compounds, therefore, causes the cleavage of the furan nucleus, producing 4-methoxy-2-hydroxy-3-ethylquinoline from (I), N-methyl-2-hydroxy-3-ethyl-γ-quinolone from (V), and 4, 7, 8-trimethoxy-2-hydroxy-3-ethylquinoline from (IV). Skimmianine used in this reduction was a sample isolated in 0.06% yield from the fresh leaves of Skimmia japonica Thunb. var. rugosa Yatabe. By the methylation of nordictamnine with diazomethane, dictamnine and isodictamnine were obtained in almost equal proportions.
