防己科植物アルカロイド研究 (第211報)

台湾産ハスノハカズラStephania japonica MIERS. のアルカロイド その4 DL-N-Methyl-O, O-diethylisococlaurineの合成およびStepholineの構造

抄録

DL-1-(p-Ethoxybenzyl)-2-methyl-6-ethoxy-7-methoxy-1, 2, 3, 4-tetrahydroisozuinoline (V) was synthesized and its infrared spectrum (in chloroform) was compared with that of L-N-methyl-O, O-diethylcoclaurine (IV). There was hardly any difference in their absorptions (Fig. 1) but their NMR spectra were clearly different (Fig. 2). The NMR spectrum of the non-phenolic base, obtained by the cleavage of O, O-diethylstepholine with metallic sodium in liquid ammonia, indicated that this base is D-N-methyl-O, O-diethylcoclaurine and not D-N-methyl-O, O-diethylisococlaurine.
Consequently, re-examinations were made on stepholine (I) and obamegine (II), and the infrared and NMR spectra of their pure compounds were found to be identical. It was also found that the difference in the melting point of stepholine (m.p. 171-173°) and of obamegine (m.p. 135-136°) was due to the addition of benzene or not. The pure compounds of these two substances melted at 171-173°, and stepholine and obamegine were found to be identical substances. Consequently, the name stepholine will henceforth be discarded.